Characterization and Utilization of Cement Kiln Dusts ... · PDF fileii Characterization and Utilization of Cement Kiln Dusts (CKDs) as Partial Replacements of Portland Cement Doctor

Characterization and Utilization of Cement Kiln Dusts (CKDs)

as Partial Replacements of Portland Cement

by

Om Shervan Khanna

A thesis submitted in conformity with the requirements

for the degree of Doctor of Philosophy

Department of Civil Engineering

University of Toronto

© Copyright by Om Shervan Khanna (2009)

ii

Characterization and Utilization of Cement Kiln Dusts (CKDs)

as Partial Replacements of Portland Cement Doctor of Philosophy, 2009

Om Shervan Khanna

Department of Civil Engineering University of Toronto

Abstract

The characteristics of cement kiln dusts (CKDs) and their effects as partial replacement

of Portland Cement (PC) were studied in this research program. The cement industry is

currently under pressure to reduce greenhouse gas (GHG) emissions and solid by-

products in the form of CKDs. The use of CKDs in concrete has the potential to

substantially reduce the environmental impact of their disposal and create significant cost

and energy savings to the cement industry.

Studies have shown that CKDs can be used as a partial substitute of PC in a range of 5 –

15%, by mass. Although the use of CKDs is promising, there is very little understanding

of their effects in CKD-PC blends. Previous studies provide variable and often

conflicting results. The reasons for the inconsistent results are not obvious due to a lack

of material characterization data. The characteristics of a CKD must be well-defined in

order to understand its potential impact in concrete.

The materials used in this study were two different types of PC (normal and moderate

sulfate resistant) and seven CKDs. The CKDs used in this study were selected to provide

a representation of those available in North America from the three major types of

cement manufacturing processes: wet, long-dry, and preheater/precalciner. The CKDs

have a wide range of chemical and physical composition based on different raw material

sources and technologies. Two fillers (limestone powder and quartz powder) were also

used to compare their effects to that of CKDs at an equivalent replacement of PC.

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The first objective of this study was to conduct a comprehensive composition analysis of

CKDs and compare their characteristics to PC. CKDs are unique materials that must be

analyzed differently from PC for accurate chemical and physical analysis. The present

study identifies the chemical and physical analytical methods that should be used for

CKDs. The study also introduced a method to quantify the relative abundance of the

different mineralogical phases within CKDs. It was found that CKDs can contain

significant amounts of amorphous material (>30%) and clinker compounds (>20%) and

small amounts of slag and/or flyash (<5%) and calcium langbeinite (<5%). The

dissolution of ionic species and composition of the liquid phase play an important role in

PC hydration. The dissolved ion contributions from CKDs were compared to PC using

dilute stirred suspensions at 10 minutes and it was found that the ion contributions from

CKDs are qualitatively the same as the ion contributions from PC, with the exception of

chloride ions.

The second objective was to utilize the material characterization analysis to determine the

relationships among the composition properties of CKD-PC blends and their effects on

fresh and hardened properties. The study found that CKDs from preheater/precalciner

kilns have different effects on workability and heat evolution than CKDs from wet and

long-dry kilns due to the presence of very reactive and high free lime contents (>20%).

The blends with the two CKDs from preheater/precalciner plants had higher paste water

demand, lower mortar flows, and higher heat generation during initial hydrolysis in

comparison to all other CKD-PC blends and control cements. The hardened properties of

CKD as a partial substitute of PC appear to be governed by the sulfate content of the

CKD-PC blend (the form of the CKD sulfate is not significant). According to analysis of

the ASTM expansion in limewater test results, the CKD-PC blend sulfate content should

be less than ~0.40% above the optimum sulfate content of the PC. It was also found that

the sulfate contribution of CKD behaves similar to gypsum. Therefore, CKD-PC blends

could be optimized for sulfate content by using CKD as a partial substitute of gypsum

during the grinding process to control the early hydration of C3A. The wet and long-dry

kiln CKDs contain significant amounts of calcium carbonate (>20%) which could also be

used as partial replacement of limestone filler in PC.

iv

Acknowledgments

I wish to express my sincere gratitude to Professor Doug Hooton, my supervisor, for his

excellent guidance and invaluable advice during this investigation. Thanks are also due to

Professor Hooton for the facilities extended to me at University of Toronto.

This project was initiated by the Products and Quality Department of Lafarge North

America Centre for Technical Services in Montreal under the guidance of Mr. Bruce

Blair, Dr. Anik Delagrave, and Ms. Claude Lauzon. Acknowledgement is made of their

generous assistance and valuable cooperation throughout the research program. I wish to

extend my deepest thanks and appreciation to Dr. Laurent Barcelo of Lafarge North

America for his helpful suggestions and interest in this investigation. Dr. Barcelo also

reviewed this manuscript during the preparation of the dissertation. Thanks are also

extended to these Lafarge personnel who shared their technical knowledge and expertise

via personal meetings and/or email exchanges: Dr. Jean Philippe Perez, Dr. Ellis Gartner,

and Mr. Paul Lehoux. Thanks are due to Lafarge laboratory technicians Rino Lisella and

Patricia Martin who shared their expertise and helped in preparing many of the

specimens. Thanks also to the many other laboratory researchers and staff of Lafarge for

providing assistance: Mr. Denis Belanger, Mr. Denis Leblanc, Ms. Sona Babikan, Mr.

Claude Verville, Ms. Julie Morissette, Ms. Lorraine Phang, and Mr. Bernard Brochard.

Thanks are also due to my colleagues at the University of Toronto. I wish to extend my

gratitude to Dr. Terry Ramlochan for providing technical advice periodically throughout

the course of this project, particularly with the CKD phase quantification. I would also

like to acknowledge the help provided by other members of the Concrete Materials

Group: Dr. Gustavo Julio-Betancourt for his helpful discussions, and Ms. Ursula Nytko

and Ms. Olga Perebatova for providing guidance and help with the materials and

equipment. Thanks are also due to Dr. S. Petrov from the Department of Chemistry for

assisting with the CKD phase quantification and Mr. Dan Mathers from the Department

of Chemistry for his help in analyzing some of the solution samples.

v

Sincere thanks to my supervising committee members Dr. Brenda McCabe and Dr.

Murray Grabinsky for their insightful questions and comments while the thesis was in

progress. I would also like to thank Dr. Daman Panesar for very supportive discussions

during my Ph.D and reviewing this dissertation.

Further, the author is indebted to Lafarge North America, the Natural Sciences and

Engineering Research Council (NSERC), and the Ontario Graduate Scholarship (OGS)

Program for providing financial support throughout the project.

My thanks are also due to my wife, children, and family members for their support and

understanding throughout the course of this project.

vi

Table of Contents

1.0 INTRODUCTION .................................................................................................. 1

1.1 Background ......................................................................................................... 1

1.2 Problem Statement .............................................................................................. 2

1.3 Incentives and Objectives of This Study ............................................................ 4

1.4 Summary of Chapters ......................................................................................... 6

2.0 LITERATURE REVIEW ....................................................................................... 8

2.1 CKD Manufacture and Management .................................................................. 8

2.1.1 Portland Cement Manufacture Overview ................................................... 8

2.1.2 CKD Generation ....................................................................................... 17

2.1.3 Fresh and Landfill CKD............................................................................ 20

2.1.4 CKD Applications: Cement Industry Perspective .................................... 21

2.1.5 Costs Associated with CKD Disposal....................................................... 22

2.1.6 CKD Environmental Considerations ........................................................ 23

2.2 CKD and Portland Cement ............................................................................... 24

2.2.1 Chemical Properties .................................................................................. 24

2.2.2 Mineralogical Properties........................................................................... 26

2.2.3 Physical Properties.................................................................................... 29

2.2.4 CKD Types ............................................................................................... 32

2.2.5 Variability of CKD from a Single Plant ................................................... 34

2.3 Portland Cement Hydration .............................................................................. 35

2.3.1 Initial Hydrolysis ...................................................................................... 37

2.3.2 Induction ................................................................................................... 38

2.3.3 Acceleration .............................................................................................. 39

2.3.4 Deceleration .............................................................................................. 40

2.3.5 Slow Continued Reaction ......................................................................... 41

2.4 Effects of CKD Properties and PC Dilution ..................................................... 41

2.4.1 Calcium Carbonate.................................................................................... 41

2.4.2 Quartz........................................................................................................ 44

2.4.3 Clays ......................................................................................................... 44

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2.4.4 Free Lime and Calcium Hydroxide........................................................... 45

2.4.5 Magnesia ................................................................................................... 48

2.4.6 Sulfate ....................................................................................................... 49

2.4.7 Chloride..................................................................................................... 54

2.4.8 Alkalis ....................................................................................................... 57

2.4.9 Clinker Phases........................................................................................... 58

2.4.10 Physical Properties.................................................................................... 58

2.5 CKD-PC............................................................................................................ 60

2.5.1 CKD-PC Material Characterization.......................................................... 62

2.5.1.1 CKD-PC Chemical Composition...................................................... 62

2.5.1.2 CKD-PC Mineralogical Composition............................................... 66

2.5.1.3 CKD-PC Physical Composition........................................................ 68

2.5.2 Workability ............................................................................................... 69

2.5.3 Setting Time.............................................................................................. 77

2.5.4 Hydration Kinetics .................................................................................... 82

2.5.5 Compressive Strength ............................................................................... 87

2.5.6 Flexural and Tensile Strength ................................................................. 103

2.5.7 Volume Stability ..................................................................................... 106

2.5.7.1 Soundness ....................................................................................... 106

2.5.7.2 Drying Shrinkage ............................................................................ 108

2.5.7.3 Volume Stability Summary............................................................. 112

2.5.8 Durability ................................................................................................ 113

2.5.8.1 Alkali-Aggregate Reaction ............................................................. 113

2.5.8.2 Steel Corrosion................................................................................ 116

2.5.8.3 Permeability .................................................................................... 121

2.5.8.4 Freezing and Thawing..................................................................... 123

2.5.8.5 External Sulfate Resistance............................................................. 125

2.5.8.6 Durability Summary........................................................................ 126

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3.0 MATERIALS AND EXPERIMENTAL DETAILS........................................... 127

3.1 Materials ......................................................................................................... 127

3.2 Testing of Raw Materials................................................................................ 129

3.2.1 Chemical Properties ................................................................................ 129

3.2.2 Mineralogical Properties......................................................................... 129

3.2.3 Physical Properties.................................................................................. 130

3.2.4 Dilute Stirred Suspensions...................................................................... 130

3.3 CKD-PC Blends.............................................................................................. 131

3.3.1 Heat of Hydration ................................................................................... 131

3.3.2 Normal Consistency................................................................................ 133

3.3.3 Initial Setting Time ................................................................................. 133

3.3.4 Flow ........................................................................................................ 134

3.3.5 Compressive Strength ............................................................................. 134

3.3.6 Expansion in Limewater ......................................................................... 134

3.3.7 Autoclave Expansion .............................................................................. 135

3.3.8 Alkali Silica Reactivity ........................................................................... 135

4.0 RESULTS AND DISCUSSION......................................................................... 138

4.1 Material Characterization................................................................................ 138

4.1.1 Chemical Properties ................................................................................ 138

4.1.2 Mineralogical Properties......................................................................... 144

4.1.3 Physical Properties.................................................................................. 151

4.1.4 CKD Dissolution Analysis...................................................................... 158

4.2 CKD-PC Blends.............................................................................................. 162

4.2.1 Kinetics ................................................................................................... 167

4.2.1.1 Heat of Hydration ........................................................................... 167

4.2.2 Physical Properties of Hydration ............................................................ 195

4.2.2.1 Normal Consistency........................................................................ 195

4.2.2.2 Flow ................................................................................................ 202

4.2.2.3 Initial Setting Time ......................................................................... 210

4.2.2.4 Compressive Strength ..................................................................... 218

4.2.3 Volume Stability and Durability............................................................. 230

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4.2.3.1 Expansion in Limewater ................................................................. 230

4.2.3.2 Autoclave Expansion ...................................................................... 236

4.2.3.3 Alkali Silica Reactivity ................................................................... 242

5.0 MAIN CONTRIBUTIONS OF THE THESIS ................................................... 246

5.1 CKD Characterization..................................................................................... 246

5.2 CKD-PC Blends.............................................................................................. 248

6.0 CONCLUSIONS................................................................................................. 252

7.0 RECOMMENDATIONS FOR FUTURE WORK ............................................. 254

8.0 REFERENCES ................................................................................................... 257

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List of Tables

Table 2.1 Kiln material transformations (Manias, 2004) 12

Table 2.2 Summary of operation data on different kiln systems (Manias, 2004) 13

Table 2.3 Melting points and relative volatiles of different compounds in the kiln burning zone (Manias, 2004) 18

Table 2.4 Typical costs associated with CKD disposal, $/tonne (Kessler, 1995) 23

Table 2.5 CKD chemical oxide composition, free lime, and loss on ignition, and statistical analysis of 63 published datasets (Sreekrishnavilasam et al., 2006) 25

Table 2.6 Portland cement chemical oxide composition, total alkali content, and loss on ignition (Tennis and Bhatty, 2006) 25

Table 2.7 Mineralogical composition of U.S. CKD samples (Hawkins et al., 2004) 27

Table 2.8 Portland cement average bogue compound and Blaine fineness in 2004 (Tennis and Bhatty, 2006) 29

Table 2.9 CKD oxide composition and statistical analysis of intermittent daily samples collected from a single kiln (long-dry process) over a 3 year period (2005 – 2008) in North America (Lafarge, 2009) 34

Table 2.10 Summary of previous CKD-PC studies from literature review 61

Table 2.11 Chemical and physical composition of CKD: from CKD-PC literature review 64

Table 2.12 Chemical and physical composition of PC: from CKD-PC literature review 65

Table 2.13 Mineralogical composition of CKD: from CKD-PC literature review 67

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Table 2.14 Workability: from CKD-PC literature review 76

Table 2.15 Setting time: from CKD-PC literature review 81

Table 2.16 Hydration: from CKD-PC literature review 86

Table 2.17 Mortar compressive strength of CKD 1 at 0%, 5%, and 10% replacement of PC 3 as a function of time (Maslehuddin et al., 2008a) 89

Table 2.18 Compressive strength: from CKD-PC literature review 100

Table 2.19 Flexural and tensile strength: from CKD-PC literature review 106

Table 2.20 Soundness: from CKD-PC literature review 108

Table 2.21 Mortar drying shrinkage with 0%, 5%, and 10% CKD 1 replacement of PC 3 (Maslehuddin et al., 2008a) 110

Table 2.22 Drying shrinkage: from CKD-PC literature review 112

Table 2.23 Alkali-aggregate reactivity: from CKD-PC literature review 115

Table 2.24 Concrete resistivity and risk of reinforcement corrosion as specified in COST 509 (Maslehuddin et al., 2008b) 118

Table 2.25 Steel corrosion: from CKD-PC literature review 120

Table 2.26 Chloride permeability of PC 1 and PC 2 with CKD 1 replacement at 0%, 5%, 10%, and 15% (Maslehuddin et al., 2008b) 122

Table 2.27 Permeability: from CKD-PC literature review 123

Table 2.28 Freezing and thawing cycles: from CKD-PC literature review 125

Table 2.29 Sulfate resistance: from CKD-PC literature review 125

Table 3.1 CKD kiln process description 128

Table 4.1 Melting points and volatility of compounds in CKDs (Manias, 2004) 139

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Table 4.2 Chemical and select physical components of PC, CKD, and filler materials (mass %) 142

Table 4.3 Cements TI and TII mineralogical composition (mass %) 145

Table 4.4 CKD mineralogical compositions using direct test methods (mass %) 146

Table 4.5 Mineralogical composition of CKD and filler materials (mass %) 148

Table 4.6 Physical properties of all materials 152

Table 4.7 Ionic concentrations of 10:1 water to solid ratio (by mass) 159

Table 4.8 Range for chemical and physical properties of Cement TI blends at 10% and 20% replacement (Theoretical calculation, mass %) 163

Table 4.9 Range for chemical and physical properties of Cement TII blends at 10% and 20% replacement (Theoretical calculation, mass %) 164

Table 4.10 Iterative process to determine the water requirement for normal consistency of (a) Cement TI and (b) Cement TII 195

Table 4.11 Range of change in water demand for normal consistency of pastes 198

Table 4.12 Range of flow for all mortars 204

Table 4.13 Compressive strength range for CKD-PC blends as percent of PC alone 222

Table 4.14 Compressive strength range for PC-filler blends as percent of PC alone 222

Table 4.15 Autoclave expansions for (a) Cement TI and (b) Cement TII 236

Table 4.16 Range of autoclave expansions for all blends 239

Table 4.17 ASR concrete mix alkali loadings and CKD replacement levels for (a) Test Series I: Cement TI CKD blends and (b) Test Series II: Cement TII CKD blends 243

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List of Figures

Figure 2.1 Cement manufacturing process (Corish and Coleman, 1995) 9

Figure 2.2 Clinker reactions in kiln feed as a function of temperature (Manias, 2004) 12

Figure 2.3 Schematic of (a) a wet and long-dry pyroprocess and (b) a preheater/precalciner pyroprocess (with a single preheater tower) (Manias, 2004) 15

Figure 2.4 Schematic of electrostatic precipitator (ESP) efficiency (Peethamparan, 2002) 19

Figure 2.5 CKD and PC particle size distribution (Peethamparan et al., 2008) 30

Figure 2.6 CKD and PC particle size distribution from published literature (Sreekrishnavilasam et al., 2006) 31

Figure 2.7 Heat evolution of PC paste during hydration stages: (1) initial reaction, (2) induction, (3) acceleration, (4) deceleration, and (5) slow continued reaction (Gartner et al., 2002) 36

Figure 2.8 Relative volumes of the major compounds in the microstructure of hydrating PC pastes as a function of time (Odler, 1998) 36

Figure 2.9 Effect of firing temperature on the heat evolution of pure free calcium oxide during hydration (Shi et al., 2002) 46

Figure 2.10 Heat of hydration of cement paste determined by isothermal conduction calorimetry, (20°C and w/c = 0.44); (a) PC (b) PC + 0.5% SO3, (c) PC + 2.5% SO3 (Lawrence, 1998b) Note: Sulfate added as Gypsum (Calcium Sulfate) 51

Figure 2.11 Optimization of gypsum additions for compressive strength at different ages (Gartner et al., 2002) (Note: this PC required higher SO3 levels than normal to obtain maximum strength) 53

Figure 2.12 Effect of calcium chloride on heat development in PC (Lerch, 1944) 56

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Figure 2.13 Relationship between water demand and specific surface area of PC (Sprung et al., 1985) 59

Figure 2.14 Particle size distribution of CKD 5 and PC 7 (Wang et al., 2002) 69

Figure 2.15 Paste water/binder ratio, initial set, and final set of CKD 2 as a partial substitute of PC 4 at different levels of replacement (El-Aleem et al., 2005) 70

Figure 2.16 Mortar water/binder ratio of CKD 2 as a partial substitute of PC 4 at different levels of replacement (El-Aleem et al., 2005) 71

Figure 2.17 Mortar water/binder ratio of CKD 3 as a partial substitute of PC 5 at different levels of replacement (Al-Harthy et al., 2003) 72

Figure 2.18 Hydration of pastes showing (a) evaporable water content (%), (b) free lime content (%) (calcium oxide and calcium hydroxide), and (c) chemically combined water content, as a function of time at different percentage levels of PC 4 replacement with CKD 2 (El-Aleem et al., 2005) 83

Figure 2.19 Concrete compressive strength of CKD 1 at different replacement levels of (a) PC 1 and (b) PC 2 (Maslehuddin et al., 2008b) 88

Figure 2.20 Mortar compressive strength as a function of time at different percentage levels of CKD 2 replacement of PC 4 (El-Aleem et al., 2005) 90

Figure 2.21 Concrete compressive strengths, w/b (a) 0.70, (b) 0.60, and (c) 0.50, at different percentage levels of CKD 3 replacement of PC 5 (Al-Harthy et al., 2003) 92

Figure 2.22 Concrete drying shrinkage as a function of time at different replacement levels of PC 1 with CKD 1 (Maslehuddin et al., 2008b) 109

Figure 2.23 Concrete drying shrinkage as a function of time at two different w/b ratios with 5% CKD 12 replacement of PC 12 (Wang and Ramakrishnan, 1990) 111

Figure 2.24 Concrete specimen variation of electrical resistivity with moisture content at different percentage levels of CKD 1 replacement of (a) PC 1 and (b) PC 2 (Maslehuddin et al., 2008b) 117

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Figure 4.1 Process flow chart for CKD chemical composition analysis 140

Figure 4.2 Particle size distribution of PC, CKD and filler. The materials are in the direction and position of the arrow: LS, D, SLX, TII, TI, A, F, C, E, B, D* 155

Figure 4.3 Particle size distribution of PC, CKD and filler between 0.1 µm and 10 µm. The materials are in the direction of the arrow: LS, SLX, C, D, B, A, F, TII, TI, E, D* 155

Figure 4.4 CKD fineness correlation between (a) Blaine fineness and particle size distribution, and (b) percentage passing 45µm sieve and particle size distribution 156

Figure 4.5 Composition of pore solution w/b 0.5 high alkali PC paste (Gartner et al., 2002) 158

Figure 4.6 Schematic of isothermal conduction calorimetry curve heat liberation characterization 168

Figure 4.7 Cumulative heat of hydration during initial hydrolysis (Ai) of (a) Cement TI blends and (b) Cement TII blends (w/b = 0.4, 23°C) 170

Figure 4.8 Cumulative heat of hydration during initial hydrolysis (Ai) as a function of Free CaO (%) for (a) Cement TI CKD blends and (b) Cement TII CKD blends (w/b = 0.4, 23°C) 171

Figure 4.9 Cumulative heat of hydration during initial hydrolysis (Ai) as a function of (a) sulfate content for Cement TI CKD blends and (b) alkali content for Cement TII CKD blends (w/b = 0.4, 23°C) 173

Figure 4.10 Minimum heat of hydration rate during induction period (Qi) of (a) Cement TI blends and (b) Cement TII blends (w/b = 0.4, 23°C) 175

Figure 4.11 Minimum heat of hydration rate during induction period (Qi) as a function of sulfate content for (a) Cement TI CKD blends and (b) Cement TII CKD blends (w/b = 0.4, 23°C) 176

Figure 4.12 Minimum heat of hydration rate during induction period (Qi) as a function of calcium langbeinite content for (a) Cement TI CKD blends and (b) Cement TII CKD blends (w/b = 0.4, 23°C) 177

xvi

Figure 4.13 Time of minimum heat of hydration rate during the induction period (ti) of (a) Cement TI blends and (b) Cement TII blends (w/b = 0.4, 23°C) 179

Figure 4.14 Time of minimum heat of hydration rate during the induction period (ti) as a function of total alkali content for (a) Cement TI CKD blends and (b) Cement TII CKD blends (w/b = 0.4, 23°C) 180

Figure 4.15 Main hydration peak relative to the minimum peak rate heat of hydration during the induction period (Qw-Qi) for (a) Cement TI blends and (b) Cement TII blends (w/b = 0.4, 23°C) 182

Figure 4.16 Main hydration peak relative to the minimum peak rate heat of hydration during the induction period (Qw-Qi) as a function of calcium langbeinite content for (a) Cement TI CKD blends and (b) Cement TII CKD blends (w/b = 0.4, 23°C) 184

Figure 4.17 Heat of hydration for Cement TI with (a) CKD A and LS at 10% replacements, (b) CKD C and LS at 10% replacements, (c) 0% and LS at 20% replacements, and (d) CKD B and LS at 20% replacements (w/b = 0.4, 23°C) 186

Figure 4.18 Heat of hydration for Cement TI with (a) 0% and LS at 10% replacements and (b) CKD E and LS at 20% replacements (w/b = 0.4, 23°C) 188

Figure 4.19 Heat of hydration for Cement TII with (a) 0% and LS at 10% replacements, (b) CKD C and LS at 10% replacements, and (c) CKD C and LS at 20% replacements (w/b = 0.4, 23°C) 189

Figure 4.20 The total heat generation from induction period to 7 days hydration (A7d-Ai) for (a) Cement TI blends and (b) Cement TII blends (w/b = 0.4, 23°C) 191

Figure 4.21 Water requirement for normal consistency of (a) Cement TI blends and (b) Cement TII blends 197

Figure 4.22 Correlation between Cement TI and Cement TII blends with the same CKD and replacement level for (a) all CKDs and (b) CKDs A, B, C, and D 199

xvii

Figure 4.23 Water requirement for normal consistency as a function of free lime content for (a) Cement TI CKD blends and (b) Cement TII CKD blends 200

Figure 4.24 Mortar flow of (a) Cement TI blends and (b) Cement TII blends 203

Figure 4.25 Mortar flow as a function of free lime content for (a) Cement TI CKD blends and (b) Cement TII CKD blends 206

Figure 4.26 Mortar flow as a function of (a) percentage of volume less than 30.5 µm for Cement TI CKD blends (excluding CKDs E and F) (b) percentage passing 45 µm for Cement TII blends (excluding CKDs E and F) 207

Figure 4.27 Initial set time for (a) Cement TI blends and (b) Cement TII blends 211

Figure 4.28 Initial set time as a function of the time of minimum heat rate during the induction period (ti) for (a) Cement TI CKD blends (excluding circled data points) and (b) Cement TII CKD blends 214

Figure 4.29 Initial set time as a function of soluble alkali content for (a) Cement TI blends (excluding circled data points) and (b) Cement TII blends 216

Figure 4.30 Mortar compressive strength of Cement TI blends at 1, 3, 7, 28, and 90 days (w/b = 0.485) for (a) 10% replacement and (b) 20% replacement (w/b = 0.485) 220

Figure 4.31 Mortar compressive strength of Cement TI blends at 1, 3, 7, 28, and 90 days (w/b = 0.485) for (a) 10% replacement and (b) 20% replacement (w/b = 0.485) 221

Figure 4.32 Mortar compressive strength as a function of total sulfate content for Cement TI CKD blends at (a) 1 day and (b) 3 days (w/b = 0.485) 224

Figure 4.33 Mortar compressive strength as a function of total sulfate content for Cement TII CKD blends at (a) 1 day and (b) 3 days (w/b = 0.485) 226

Figure 4.34 Mortar compressive strength at 28 days as a function of percentage passing 45 µm for Cement TI CKD blends 228

xviii

Figure 4.35 Mortar compressive strength at 28 days as a function of calcite for Cement TII CKD blends (w/b = 0.485) 228

Figure 4.36 Expansion in limewater after 14 days for (a) Cement TI blends and (b) Cement TII blends 233

Figure 4.37 Expansion in limewater at 14 days as a function of sulfate content for (a) Cement TI CKD blends and (b) Cement TII CKD blends 234

Figure 4.38 Autoclave Expansions for (a) Cement TI blends and (b) Cement TII blends 238

Figure 4.39 Autoclave expansion as a function of free lime content (excluding data points in the circles) for (a) Cement TI CKD blends and (b) Cement TII CKD blends 240

Figure 4.40 ASR expansions over 2 years for (a) Test Series I: Cement TI CKD blends and (b) Test Series II: Cement TII CKD blends 245

xix

List of Appendices

Appendix A. CKD Chemical Composition Correction Calculations

Appendix B. PC and CKD TGA Analysis

Appendix C. CKD XRD Scans

Appendix D. PC, CKD-PC, and PC-Filler Properties

Appendix E. Isothermal Conduction Calorimetry Results

Appendix F. Mortar Flow Statistical Analysis

Appendix G. Mortar Compressive Strength Statistical Analysis

Appendix H. Mortar Expansion in Limewater Statistical Analysis

xx

List of Notation

The following notations are commonly used throughout this thesis: General

AAR Alkali-Aggregate Reaction

AASHTO American Association of State and Highway Transportation

Officials

ANOVA Analysis of Variance

ASR Alkali-Silica Reaction

ASTM American Society for Testing Materials

BS British Standard

CKD Cement Kiln Dust

CSA Canadian Standards Association

EPA Environmental Protection Agency (U.S.)

ESP Electrostatic Precipitators

GHG Greenhouse Gas

ISAT Initial Surface Absorption Test

LOI Loss on Ignition

NCHRP National Cooperative Highway Research Program

PC Portland Cement

PCA Portland Cement Association

PSD Particle Size Distribution

SCM Supplementary Cementitious Material

TCLP Toxicity Characteristic Leaching Procedure

TGA Thermal Gravimetric Analysis

XRD X-ray Diffraction

xxi

Chemical

AFm Aluminate-Ferrite-Monosubstituted, Monosulphoaluminate, or

Monosulphate

AFt Aluminate-Ferrite-Trisubstituted or Ettringite

C3S Tricalcium Silicate or Alite

C2S Dicalcium Silicate or Belite

C3A Tricalcium Aluminate or Aluminate

C4AF Tetracalcium Aluminate Ferrite or Ferrite

CH Calcium Hydroxide

C-S-H Calcium Silicate Hydrate

Na2Oe Equivalent Na2O (Na2O + 0.658 K2O) (mass %)

1

1.0 INTRODUCTION

1.1 Background

There are currently many challenges to the utilization of by-product cement kiln dusts

(CKDs) as partial replacement of Portland cement (PC). CKDs are fine powders (CKDs

typically have between 80 and 90% passing a 90 µm sieve) that are generated during the

cement manufacturing process, then carried off in the flue gases, and subsequently

collected in baghouses or electrostatic precipitators. The portion of CKDs that are not

returned back to the cement manufacture process, or otherwise used beneficially, are

placed in stockpiles or landfills. A limited number of studies have shown that CKDs

removed from the cement manufacturing process could be used as partial replacements of

PC in the range of 5 – 15%, by mass. Although standards allow for the use of CKDs at

low levels of PC replacement, very little is known about the effects of different CKDs in

pastes, mortars, and concrete. The studies that have been published on the use of CKDs

as a partial substitute of PC often report conflicting results.

Significant amounts of CKDs are placed in landfills every year. In 2000, the Portland

Cement Association (PCA) conducted a United States (U.S.) Cement Industry survey of

92 cement plants. They reported total clinker production to be 68.8 million tonnes

(clinker is the major component of PC and is typically 90 – 95% of total cement

production). The amount of CKDs removed from the cement kiln process that year for

the same 92 cement plants was 2.8 million tonnes (4.1% of clinker production). Almost

80% of the CKDs removed from cement-producing kilns were placed in landfills, while

only approximately 20% were beneficially re-used (Hawkins et al., 2004). On a global

scale, it is estimated that approximately 30 million tonnes of CKDs are removed from the

cement manufacturing process every year (Dyer et al., 1999). Approximately 25 years

ago, the CKDs in U.S. landfills were estimated to be greater than 90 million tonnes

(Collins and Emery, 1983).

2

There are many applications of CKDs that continue to be investigated: for example, as a

component in cements and masonry products, as an agricultural/soil fertilizer, as a soil

stabilizer, as a wastewater stabilizer, as a partial replacement of soda in glass production,

as an anti-stripping agent in asphalts, and as a subgrade for highway construction (Bhatty,

1995). From the perspective of the cement industry, however, the most desirable

application of CKDs that cannot be recycled back into the process is their use as a partial

replacement of PC.

1.2 Problem Statement

Four obstacles related to CKD compositions currently inhibit their use in concrete: (i)

inadequate CKD characterization, (ii) potentially deleterious interactions between CKD

and PC, (iii) unknown interactions of CKD with mineral and/or chemical admixtures, and

(iv) CKD-PC conformance to cement and concrete standards. The focus of the thesis is to

mainly address the first and second categories. Each category is briefly discussed in this

section, however, to provide the reader with a broader understanding of the problem.

In order to understand the effects of CKDs in concrete, it is essential to have a proper

characterization of an individual CKD. Comprehensive compositional analysis of a CKD

is also important for optimization of a CKD-PC blend for use in concrete field

applications. Determining the characteristics of the CKDs used in previous CKD-PC

interaction studies was not always possible due to the incomplete compositional analysis

provided. This is likely due to the insufficient and sometimes inappropriate application of

compositional analysis procedures designed for PC to determine the composition of

CKD. CKD is a unique material that has different characteristics from PC. In comparison

to PC, CKDs typically contain higher concentrations of free lime, alkalis, sulfates,

chlorides, raw materials, and trace heavy metals (Hawkins et al., 2004).

3

CKDs can influence the interactions among the basic components of concrete (PC, water,

and aggregate). The effects of the individual components found in CKDs at elevated

concentrations in concrete are generally understood. The varying concentrations of these

components in combination with each other as found in CKDs, however, are not well

understood. Therefore, it is not clear how a particular CKD will interact as a partial

replacement of a given PC. The composition of each PC can also have unique

characteristics. A given CKD may react differently with dissimilar PCs and, therefore,

result in different effects on concrete properties. It is important to understand how the

CKD-PC interaction will impact concrete properties such as workability, hydration,

setting time, strength, volume stability, and durability for optimization of a mix design in

the field.

The impact of a CKD in concrete is not limited to its interaction with PC, aggregate, and

water. The use of supplementary cementing materials (SCMs) in concrete has been

steadily increasing over the years. The presence of a CKD could influence the

mechanisms and effectiveness of SCMs and chemical admixtures in concrete. SCMs such

as slag, fly ash, and silica fume contribute to the properties of the hardened concrete

through hydraulic and/or pozzolanic action (pozzolanic action occurs when a pozzolan

combines with calcium hydroxide to exhibit cementitious properties). It has been reported

that the high alkali and sulfate content of a CKD can act as an excellent activator for

pozzolanic materials (Konsta-Gdoutos and Shah, 2003).

Chemical admixtures are also commonly used in concrete mixtures. Chemical admixtures

can be defined as materials other than water, aggregates, and hydraulic cement that are

added immediately before or during mixing of concrete. The most prominent chemical

admixtures are used to decrease the quantity of water needed to obtain a given degree of

workability or to entrain air in order to increase the resistance of concrete to damage from

freezing (Taylor, 1997). Chemical admixtures can also be used to increase workability by

dispersion of cement in the aqueous phase of concrete and to accelerate or retard the

4

normal rate of hydration (Dodson, 1990). There is little, if any, published research on the

interaction of CKDs and PC with chemical admixtures.

Cement and concrete standards include limitations on the chloride, sulfate, and alkali

content in PC and concrete to ensure acceptable performance and durability. If it is

shown that the elevated concentrations of these components in CKDs do not compromise

performance and durability in concrete, regulatory standards may need to be modified to

allow for increased amounts of their replacement of PC. In order to allow for the use of

industrial by-products such as CKDs, there is a move away from prescriptive or

compositional standards towards performance standards. ASTM C150 allows the use of

processing additions meeting the requirements of ASTM C465 for use in the manufacture

of hydraulic cements.

1.3 Incentives and Objectives of This Study

The use of CKDs as a partial replacement of cement has the potential to substantially

reduce the environmental impact of CKD disposal and create significant cost and energy

savings to the cement industry. From an environmental perspective, CKD removal from

the cement manufacturing process leads to excessive generation of gas emissions and

increased need for land disposal sites. Partial substitution of PC with CKDs would

decrease the need for clinker production and reduce the amount of energy wasted due to

partial pyropressing of CKDs. A reduction of clinker production would also reduce

greenhouse gases that are related to fuel burning and limestone decarbonation. As

environmental concerns increase, it is also important to recognize that obtaining landfill

permits is becoming increasingly difficult. The use of CKDs as a partial replacement of

cement could help minimize the size and number of landfill disposal sites.

In addition to the environmental benefits related to CKD-PC blends, reducing the clinker

factor in cement would also create several financial benefits. First, the lifespan of the

limestone quarry and other natural resources would increase. Second, the reduction of

5

raw materials required for PC production would reduce material costs and energy

consumption related to mining, crushing, and grinding. Third, a reduction of clinker

production would reduce pyroprocess, dust collection, and landfill disposal costs. Fourth,

since the CKD is already a fine powder, there will be less energy consumption in the

finish mill to achieve the target fineness compared to the energy needed to interground

clinker. Finally, the typical transport costs for other materials used for blend cements

would not be incurred since CKD is generated on the same site as the PC. It is important

to acknowledge that the cement and concrete industry may need to incur costs related to

building and maintaining systems that allow for blending of CKD with cements that meet

quality control targets.

The study of CKD as a partial replacement of PC has been a sporadic research area for

the past 30 years. The concrete industry has been very successful in utilizing other

industrial by-products – such as slag, fly ash, and silica fume – as partial replacements of

PC. Once considered to be waste products, these SCMs are now widely used to improve

the workability, strength, and durability characteristics of concrete. Although there are

many studies that report the effects of different binary and ternary blends of CKDs with

PC, silica fume, fly ash, and/or slag, it is very difficult to make conclusions regarding

performance due to conflicting results and incomplete CKD characterizations. The

reasons for the different effects of CKD-PC blends have not been thoroughly explored.

The interaction between different CKDs and PC must be well understood before

introducing chemical admixtures and other SCMs. Understanding the CKD-PC

interactions and developing appropriate limits for specific deleterious components could

ultimately allow for the standardization and optimization of blended cements with high

replacement levels (5 – 15%, by mass) of PC with CKD in concrete, leading to both

environmental and economic benefits.

6

The first objective of this study was to compare the chemical, physical, mineralogical,

and rapid ion dissolution properties of different CKDs with PC. Since there is a lack of

proper CKD characterization in previous CKD-PC blend research, the present study aims

to identify the appropriate chemical and physical analytical methods that should be used

for CKD composition analysis. Mineralogical composition analysis is a fine complement

to chemical composition analysis since the effects of CKD elements in a CKD-PC blend

may vary depending upon the form in which they actually exist. Therefore, a method to

quantify the relative abundance of the different mineralogical phases within CKDs was

introduced. Since the availability of ions in the liquid phase greatly influences PC

hydration, the rapid ion dissolutions from CKDs compared to PC were also investigated.

The second objective was to utilize the material characterization analysis to determine the

relationships among the composition properties of CKD-PC blends and their effects on

hydration, mechanical properties, and volume stability. Paste and mortar tests were used

to assess the effects of CKDs on: (i) heat of hydration, (ii) water demand, (iii) flow, (iv)

initial setting time, (v) compressive strength, (vi) expansion in limewater, and (vii)

autoclave expansion. Regression analysis was performed where possible to examine the

relationships among CKD-PC blend properties and various independent variables.

Additionally, concrete prisms were used to evaluate the impact of CKDs on a key

durability concern – alkali silica reactivity (ASR).

1.4 Summary of Chapters

The topics addressed in this study are presented in eight chapters. A brief summary of

Chapters 2 to 8 is given below.

Chapter 2 is a literature review that provides an understanding of CKD manufacture and

management; a basic understanding of CKD composition and its variability relative to

PC; a review of PC hydration and the known effects of the individual components of

CKDs in pastes, mortars, and concrete; and a review of previous studies on CKD-PC

7

interaction. All performance parameters in previous CKD-PC blend studies are presented

in order to provide a general overview of the subject, although some aspects are not part

of the current study.

Chapter 3 describes the materials and test methods used in the current study. The CKDs

selected for this study are representative of those available in North America. Various test

methods related to material characterization and CKD-PC performance used for the

experimental program are described.

Chapter 4 presents the results and discussions of the current study. The first part of this

chapter explores the material characterization and analytical methods used to determine

accurate CKD characterizations. The second part of this chapter focuses on the effects

and relationships of using CKDs as a partial replacement of PC on heat of hydration,

workability, setting time, compressive strength, expansion in limewater, and soundness.

Additionally, it also discusses the impact of CKDs on ASR.

Chapter 5 highlights the main contributions of the thesis, giving a thorough explanation

of the value of the research that was conducted. In Chapter 6 the conclusions of the

thesis are presented.

Chapter 7 provides recommendations for future research that will enhance the use of

CKDs in concrete. This research study is a first step towards a comprehensive

understanding of how CKD-PC blends can be optimized.

Chapter 8 provides the list of the references that were consulted in the process of research

for the thesis.

8

2.0 LITERATURE REVIEW

2.1 CKD Manufacture and Management

2.1.1 Portland Cement Manufacture Overview

A critical examination of CKD utilization as a partial replacement of PC cannot be

conducted without an understanding of basic cement manufacturing. The composition

and variability of a CKD produced at a plant is directly related to the cement

manufacturing process at that plant. PC is produced by burning ground mixtures of

limestone and other materials up to high temperatures (greater than 1450˚C) in a rotary

kiln to form clinker (Manias, 2004). The clinker is cooled and then ground in a finish mill

along with a small amount of gypsum to make a gray powder called PC. ASTM C219

defines PC as “a hydraulic cement produced by pulverizing Portland-cement clinker, and

usually containing calcium sulfate”. Low levels of mineral additives such as limestone,

however, are increasingly common in PC. Clinker consists of predominantly crystalline

calcium silicates. Hydraulic means that it sets and hardens by chemical interaction with

water. Although every plant has significant differences in equipment design and

operation, the chemical and physical transformation of raw materials into PC is

essentially the same at all cement plants. The basic steps of cement manufacturing are

illustrated in Figure 2.1.

The principal raw mix components that are required for the production of clinker are

calcium, silica, aluminum, and iron (Taylor, 1997). Calcium carbonate and argillaceous

substances (clay) are naturally occurring raw materials that typically contain the principal

chemical elements. Limestone, the most common form of calcium carbonate, is the usual

calcium source for cement manufacturing. Other forms of calcium carbonate such as

chalk, shell deposits, and calcareous muds can also be used. Clays are essentially hydrous

aluminum silicates with complete or partial substitution of magnesium and/or iron in

9

place of aluminum in certain minerals. Alkalis or alkaline earths are also present as

essential constituents in clays (Chatterjee, 2004). The natural raw materials are

traditionally mined at quarries close to the cement plant. At times, auxiliary raw materials

that contain iron, alumina, and/or silica are required in order to achieve the proper raw

mix proportion. Blast furnace slag, fly ash, iron oxide, bauxite, and spent catalysts are

widely used auxiliary raw materials (Bhatty and Gajda, 2004).

Figure 2.1 Cement manufacturing process (Corish and Coleman, 1995)

A finely ground mixture typically consisting of approximately 75% calcium carbonate,

15% silicon dioxide, 3% aluminum oxide, and 2% iron oxide provides the major

components in the raw materials. The raw materials also contain a certain amount of

volatiles (less then 5% by mass). Some of these volatiles are alkalis (potassium oxide and

sodium oxide), sulfur, and chloride (Taylor, 1997). In addition to the major elements

10

which make up cement, smaller concentrations of almost every other element will be

present in the raw materials. Magnesium, titanium, manganese, and phosphorous are

common but they are minimized to prevent potentially deleterious effects on cement

burning and quality. Minor trace metals can also be present in the raw materials but are

also kept at low levels to avoid adverse effects (Bhatty, 2004).

In an open quarry, limestone mining operations begin with removal of overburden (waste

rock) by bulldozers to expose the top surface of the limestone. Drills are used to create

deep holes close to the open face of the limestone quarry for dynamite placement. The

limestone rock is then blasted with the dynamite to reduce its maximum diameter to

between approximately 1 and 2 metres. Front-end loaders load the blast rock into trucks

or railroad cars to be sent to the crushing system. The primary and secondary crushing

systems reduce the limestone size to between approximately 10 mm and 50 mm in

diameter (Chatterjee, 2004).

The crushed limestone and other raw materials are fed into a grinding mill to obtain the

correct size and composition for the raw mix. In the wet process, the raw materials are

mixed with approximately 30 – 40% water during grinding to form a slurry. The

composition of earth minerals in limestone and clays can be quite variable and may

require substantial blending and analysis to maintain a homogenous mixture.

Homogeneity of the raw mix is essential for quality control and plant efficiency. The wet

process homogenization system utilizes mechanical and/or pneumatic systems to agitate,

blend, and store the homogenized raw mix in cylindrical tanks or basins until it is fed into

the pyroprocessing system. The most common homogenization system used for dry

process cement plants over the past several decades is the pneumatic system based on the

air fluidization method. The homogenized raw mix is commonly referred to as kiln feed

(Chatterjee, 2004).

11

The pyroprocess is the focal point of the cement manufacturing process. Rotary kilns are

long, cylindrical, and slightly inclined (3 – 4%) furnaces that are lined with refractory

bricks to protect the steel shell and retain heat within the kiln (Manias, 2004). The kiln

feed is fed into the upper end of the kiln that rotates on its longitudinal axis. The fuels for

the kiln are burned at the lower end of the kiln. As the kiln feed enters the pyroprocess

the materials are gradually heated to form calcium oxide, which combines with silicon

dioxide at temperatures exceeding 1400oC in the kiln. Alumina and iron act as fluxing

agents, lowering the reaction temperature of the mix to a practical firing temperature.

Although there are many different kiln system designs, all kiln feed undergoes the same

reactions during the pyroprocess to form clinker – the hard pellets that typically range in

size from 0.3 to 5.1 cm in diameter. The chemical and physical transformations of the

kiln feed to clinker are quite complex, but can be viewed conceptually as the sequential

events listed in Table 2.1 (Manias, 2004).

The four major compounds of clinker that constitute approximately 95% of the clinker,

by mass are: tricalcium silicate (C3S) (35 – 65%), dicalcium silicate (C2S) (10 – 40%),

tricalcium aluminate (C3A) (0 – 15%), and tetracalcium aluminoferrite (C4AF) (5 – 15%)

(Taylor, 1997). C3S and C2S are commonly referred to as alite (impure C3S) and belite

(impure C2S), respectively. Alite typically contains 3 – 4% of substituent oxides, the most

significant of which are Fe2O3, MgO, and Al2O3. Belite may contain 4 – 6% of

substituent oxides of which Al2O3 and Fe2O3 are most common (Taylor, 1997). Alite and

belite constitute about 65 – 75% of PC and the combined total content of the four

principal clinker compounds in PC is approximately 85%. Cement chemistry

nomenclature abbreviations are as follows: C = CaO, S = SiO2, A=Al2O3, and F=Fe2O3.

Several other compounds – such as alkali sulfate and calcium oxide – are present in

minor amounts. Figure 2.2 shows the phase transformation of kiln feed to clinker at

different stages within the pyroprocess (Manias, 2004).

12

Table 2.1 Kiln material transformations (Manias, 2004)

Temperature, ˚C Material Transformation

100 Evaporation of free water

100-300 Removal of adsorbed water in clay materials

450-900 Removal of chemically bound water

700-850 Calcination of carbonate materials

800-1250 Formation of belite (C2S), aluminates, and ferrites

>1250 Formation of liquid phase melt

1330-1450 Formation of alite (C3S)

1300-1240 Cooling of clinker to solidify liquid phase

1250-100 Clinker cooled in cooler

Figure 2.2 Clinker reactions in kiln feed as a function of temperature (Manias, 2004)

13

The pyroprocess is the most energy intensive component of the overall manufacturing

process. The most commonly used fuels are coal, natural gas, and oil. Coal can contain

significant quantities of sulfur, trace metals, and other halogens that can influence the

clinker composition as well as kiln operation dynamics. Natural gas and oil typically

contain less sulfur for an equal amount of calorific energy. The use of supplemental fuels

– such as petroleum coke, used tires, impregnated sawdust, waste oils, lubricants, sewage

sludge, metal cutting fluids, and waste solvents – has expanded in recent years. Minor

trace elements from these supplemental fuels can influence clinker composition and kiln

performance (Greco et al., 2004).

The pyroprocess at each cement plant can differ substantially depending on the state of

technological advancement and the raw materials used. The three major types of kiln

pyroprocessing for cement manufacturing in North America are: wet, long-dry, and

preheater/precalciner. The main kiln design, production, and energy consumption

characteristics for each process are provided in Table 2.2. An important common aspect

of different cement pyroprocesses is the presence of the burning zone where the flame

temperatures exceeds 1400oC (Manias, 2004).

Table 2.2 Summary of operation data on different kiln systems (Manias, 2004)

Kiln Systems rpm tpd/m3 Length/Diameter

Specific Fuel Consumption,

kcal/kg kWh/t

Residence Time

minutes

Wet 1 0.45-0.8 30-35 1300-1650 17-25 180-240

Long-dry 1 0.5-0.8 30-35 1100-1300 20-30 180-240

Preheater 2 1.5-2.2 14-16 750-900 25 30-40

Precalciner 3.6 3.5-5.0 10-14 720-850 25 20-30

rpm: revolutions per minute

tpd/m3: clinker produced in tonnes per day cubic metre

kWh/t: electric energy consumed in kilowatt hour per tonne of clinker

14

In the wet and long-dry processes the entire pyroprocess occurs in the kiln, as shown in

Figure 2.3(a). In the wet process the raw materials are introduced to the kiln as slurry

containing 30 – 40% water, which results in a relatively high energy consumption (El-

Sayed et al., 1991). The kiln usually has a system of chains near the feed end of the kiln

to improve heat transfer from hot gases to the solid materials. Kiln rotation allows the

chains to be exposed to the hot gases, and they transfer heat to the cooler materials at the

bottom of the kiln. The long-dry kiln process is a newer technology than the wet process;

while both processes are similar, the long-dry kiln feed is dry. The long-dry kiln process

is the most widely used process for clinker production today and is more energy efficient

than the wet process (Manias, 2004).

Due to higher energy prices and improved technology, the design of long-dry kiln

systems has evolved into a process consisting of a preheater with a number of cyclone

stages (five or, in modern kiln systems, even six) to promote heat exchange between the

hot kiln exit gases at 1000°C and the incoming dry kiln feed, as shown in Figure 2.3(b).

Calcination (decarbonation) is the decomposition of calcium carbonate to free calcium

oxide. The material entering the rotary kiln section is already at around 800°C and partly

calcined (20 – 30%) with some of the clinker phases already present. The improved heat

transfer allows the length of the kiln to be reduced, relative to the length of kilns in the

wet and long-dry kiln processes. In recent decades, the precalcination technology has also

been introduced as an energy saving measure and is a modification of the preheater

process. In the precalciner process, the combustion air for burning fuel in the preheater no

longer passes through the kiln, but is taken from the cooler region by a special tertiary air

duct to a specially designed combustion vessel in the preheater tower. Typically, 60% of

the total fuel is burnt in the calciner, and the kiln feed is more than 90% decarbonated

before it reaches the rotary kiln section allowing for increased efficiency (Manias, 2004).

15

(a)

(b)

Figure 2.3 Schematic of (a) a wet and long-dry pyroprocess and (b) a

preheater/precalciner pyroprocess (with a single preheater tower) (Manias, 2004)

16

The final component of all pyroprocess systems is the clinker cooler. The most common

types of clinker coolers are rotary, planetary, and reciprocating grate. The clinker is

cooled from approximately 1250°C to 100°C by ambient air. The air passes through the

bed of clinker and then passes into the kiln for use as combustion air. Clinker that is

cooled rapidly typically results in a higher quality clinker (Peray, 1986).

The last step of PC manufacturing is the blending and grinding of clinker and up to 5% –

6% calcium sulfate in a ball or tube mill (finish mill). Calcium sulfate, typically in the

form of gypsum and/or natural anhydrite, is generally acquired from a source external to

the cement plant. The finish mill reduces the size of the clinker and calcium sulfate to a

maximum diameter of 100 micrometers and consumes a large portion of the electric

energy in the cement manufacturing process (30 to 50 kWh/ton of cement). The total

electric energy consumption to make PC is between 110 and 130 kWh/ton of cement.

(Hawkins et al., 2004).

CKDs are removed from the pyroprocess mostly for quality control and/or stable

operation of the kiln (CKD removal from the pyroprocess is discussed in further detail in

the following section). The U.S. cement plant average rate of CKD removal from the

manufacturing process has been reported to be 11.5% of clinker production for wet kilns,

10.5% of clinker production for long-dry kilns, and 4.0% of clinker production for

preheater/precalciner kilns (EPA, 1993). It appears that the development of

preheater/precalciner systems has resulted in significantly lower amounts of CKDs

removed from the pyroprocess per tonne of clinker relative to the wet and long-dry kiln

processes.

17

2.1.2 CKD Generation

CKDs are a fine by-product of the PC rotary kiln production operation that is captured in

the air pollution control dust collection system. As kiln feed travels through the kiln, the

finest particles of the raw materials, partially processed feed, and components of the final

product are entrained in the combustion gases flowing countercurrent to the feed. The

particulates and combustion gas precipitates that are removed from the gas stream by air

pollution dust collection systems are collectively referred to as CKD (Hawkins et al.,

2004).

Many cement plants return all or a portion of the CKD from the dust collection system to

the pyroprocess with kiln feed or at mid-kiln with dust scoops. The most desirable

application of CKDs is to introduce as much as possible back into the clinker production

cycle. The CKDs that are not returned as a pyroprocess input or otherwise used

beneficially are placed in landfills (Hawkins et al., 2004). Although it is difficult to

quantify a direct correlation between dust generation and plant operation, the amount of

CKD generated strongly depends upon the type of process and design of gas velocities in

the kiln. Other factors include kiln feed composition, fuel composition, kiln operation,

and type of dust collection system (Bhatty, 1995).

The raw materials and fuel inputs can have a significant impact on the chemical

composition and amount of CKD removed from the pyroprocess. If the raw material

and/or fuel inputs contain substantial amounts of volatiles (sodium, potassium, chloride,

and/or sulfur), a higher quantity of CKD will likely be generated in the pyroprocess.

These elements partially or completely volatilize in the sintering/burning zone close to

the flame and are collected in the gas stream flowing counter-current to kiln feed

(Hawkins et. al., 2004). Some of the volatile compounds cannot readily exit the

pyroprocess with the gas stream because they condense in the cooler parts of the system.

As volatile compounds pass through the melting, vapourizing, and condensing cycle,

their concentration in the pyroprocess can increase to the point where they can be

18

catalysts for undesirable coating buildup and ring formation in the kiln. The melting

points and relative volatilities of common kiln volatile compounds are shown in Table

2.3. Materials that volatilize in the burning zone will tend to accumulate onto the surfaces

of smaller particles of kiln feed in the cooler parts of the pyroprocess or remain in the gas

stream and be collected in the dust collectors as a CKD (Manias, 2004).

Table 2.3 Melting points and relative volatiles of different compounds in the kiln burning

zone (Manias, 2004)

Volatile Compounds Melting Point, ˚C Range of volatility*, %

CaCl2 772 60 to 80

KCl 776 60 to 80

NaCl 801 50 to 60

Na2SO4 884 35 to 50

K2SO4 1069 40 to 60

CaSO4 1280 ---

*Range of volatility: % of compound that will volatilize at melting point

The location at which a CKD is extracted from the pyroprocess also has an impact on its

characteristics. For example, preheater and precalciner kilns typically extract the CKDs

with an alkali/chloride bypass system that is located between the preheater tower and the

kiln feed end of the rotary kiln. The temperatures in this region are very different from

the temperatures that CKDs are exposed to in the wet and long-dry kiln processes and

this gives it unique characteristics. In the bypass system, a portion of the kiln exit gas

stream is removed and quickly cooled by air or water to condense the volatiles to fine

particles (Manias, 2004).

19

The CKD particles in the kiln exit gas stream of all pyroprocess are removed by dust

collection systems. Common kiln dust collection systems include electrostatic

precipitators (ESPs), baghouses, and cyclones. Kiln processes equipped with ESPs

separate the CKD in multiple electric fields as illustrated in Figure 2.4. The CKD

collected in the subsequent fields are generally smaller in size and tend to have higher

concentrations of volatiles than the coarser CKD particles. Therefore, it is possible to

return the less volatile CKD from the first fields to the pyroprocess and remove the more

volatile CKD in the last fields. Baghouses and cyclones do not allow for segregation of

CKD based upon volatile concentration.

Figure 2.4 Schematic of electrostatic precipitator (ESP) efficiency (Peethamparan, 2002)

20

There are three major reasons for removal of CKD from the pyroprocess (Kessler, 1995).

First, clinker quality must be maintained. For example, the level of alkalis, chlorides,

and/or sulfates in the raw materials may be higher than the quality control targets and,

therefore, a portion of CKD would need to be removed to reduce the concentration of

volatiles. Second, a portion of CKD may need to be removed to maintain stability of the

kiln process. As previously discussed in this section, volatiles at high concentrations in

the kiln can cause severe material build-up. This can lead to challenging operational

problems such as instability, production loss, and blockage, even to the point where the

kiln must be shut down (Peray, 1986). The third major reason for removal of CKD from

the pyroprocess is due to the lack of a mechanism to return the CKD to the kiln. This is

more prevalent in wet process cement plants that were designed and built when the

manufacturing challenges and costs associated with recycling CKD back to the kiln from

the dust collection system were greater than the costs of removing CKD from the

pyroprocess and placing it in landfills.

2.1.3 Fresh and Landfill CKD

Fresh CKDs are generally difficult to handle because of their fine, dry, powdery nature

and caustic characteristics. The addition of water to mitigate blowing and dusting

problems during transport of fresh CKDs to landfills is common. Adding water at this

stage can cause hydration of the free lime and significantly reduce possible cementitious

potential for other applications. CKD landfills normally represent many years of cement

production. They are usually found in very large above-ground stockpiles or backfill

quarries. The surface of the landfill site typically crusts over and becomes hard while the

interior of the pile can stay relatively loose. Some of the interior material can remain

unhydrated, even after many years, if exposure to moisture is limited. CKD landfills are

usually located relatively close to the cement manufacturing plants and vary in age and

composition. Exposure to the elements (moisture in particular) reduces the chemical

reactivity of the kiln dusts thereby making landfill CKD composition very different from

that of fresh CKD.

21

Fresh CKD and landfill CKD should be assessed independently for their potential use as

a partial replacement of PC. Changes in composition can occur when CKDs are subject to

weather conditions and compaction procedures. In addition to converting lime to calcium

hydroxide, exposure to the natural environment could also decompose calcium

langbeinite into syngenite and gypsum. The particle size of a CKD can also change due to

hydration and compaction. These changes could have large effects on the hydration of a

CKD-PC blend.

There are large amounts of CKDs in stockpiles and landfills that are a potential source for

CKD applications. The process of utilizing landfill CKDs, however, can be very

challenging. Landfill CKDs will often harden and require crushing and screening

equipment to remove over-sized pieces as well as any waste that may have become

combined with the CKDs.

2.1.4 CKD Applications: Cement Industry Perspective

The cement industry has a keen interest in finding practical applications for CKDs in

order to reduce costs and environmental concerns related to managing their removal from

the pyroprocess. ASTM D5050 lists several beneficial applications of CKD that include:

soil fertilization, soil stabilization, raw material for glass manufacture, sewage and

wastewater treatment, and waste pollution control.

Although there have been significant developments in the use of CKDs, large amounts

continue to be placed in landfills each year. Researchers continue to investigate the use of

CKDs in several fields. In particular, the use of CKDs as a partial replacement of

traditional construction materials continues to be an area of active interest. A number of

researchers have investigated the use of CKDs for subgrade consolidation for highway

construction, cement and masonry products, contaminated soil and sludge stabilization,

and partial replacement of asphalt. Most of the previous research on CKD applications

22

has been conducted using fresh CKDs while the issue of using CKDs from landfills and

stockpiles has not been explored in great detail (Sreekrishnavilasam et al., 2006).

From the perspective of the cement industry, the most beneficial utilization of CKDs that

are removed from the pyroprocess is as partial replacement of PC. ASTM currently

authorizes the use of processing additions, including CKDs, as a partial replacement of

PC provided that the blend complies with the requirements of ASTM C150 and ASTM

C465. The American Association of State Highway and Transportation Officials

(AASHTO) limits the amount of processing addition to 1% of the total blend. Canadian

Standards Association (CSA) has similar standards as ASTM, but if the processing

addition is above 1% of the total blend, the nature and amount of processing addition in

the finished product must be provided. At the time of writing this thesis, the National

Cooperative Highway Research Program (NCHRP) 18-11 “Improved Specifications and

Protocols for Acceptance Tests on Processing Additions in Cement Manufacturing” is

preparing a report recommending that up to 5% of a processing addition can be used as a

partial replacement of PC provided that the blend complies with the requirements of

ASTM C150 and ASTM C465. (CKDs are one of the processing addition materials

assessed as part of the NCHRP study.)

2.1.5 Costs Associated with CKD Disposal

The typical costs associated with CKD disposal in the U.S. in 1995 are presented in Table

2.4. The average cost for CKD disposal, adjusting for inflation increases over 13 years at

approximately 2.62% per year and converting short tons to tonnes, is $21.60/tonne in

2008 U.S. Dollars. The average annual clinker production of a cement plant in the U.S. is

approximately 800,000 tonnes. As an example, the cost of CKD disposal for a U.S. long-

dry kiln that produces 800,000 tonnes of clinker and removes CKD at 10.5% of clinker

production in 2008 is approximately $1.8 million dollars per year. The cost to manage

CKD disposal for a Canadian cement plant under the same conditions is comparable.

23

Table 2.4 Typical costs associated with CKD disposal, $/tonne (Kessler, 1995)

Items Low Average High

Raw Material Costs $1.50 $4.00 $5.50

Kiln Feed Costs: Crushing, Conveying, Drying, and Grinding $3.00 $4.50 $6.00

Kiln Fuel Costs: Dust Calcination and Sensible Heat $1.00 $1.50 $2.00

CKD Transport: Conveying, Hauling, and Dedusting $0.50 $1.00 $1.50

Landfill Maintenance: Monitoring, Pile Maintenance, and Closing $1.00 $3.00 $5.00

Total $7.00 $14.00 $20.00

2.1.6 CKD Environmental Considerations

The United States Environmental Protection Agency (EPA) has conducted extensive

studies on the issues of production of fresh CKDs and management of stockpile and

landfill CKDs. Fugitive dust emissions, surface water pollution, and groundwater

pollution have been addressed in these studies. In recent years, hazardous waste has been

used as a fuel in cement kiln operations. The use of waste materials in cement kiln

operations has raised concerns regarding the accumulation of heavy metals in CKD

generated by plants that use these alternative materials.

The EPA (1993) has classified CKDs as a non-hazardous material under the Bevill’s

Amendment; however, it also stated that the runoff from CKD storage and landfill piles

has the potential to generate leachate containing hazardous characteristics. Runoff and

precipitation from CKD piles have exhibited pH levels above 12.5, which can be highly

corrosive. The EPA has also expressed apprehension regarding uncontrolled transport,

storage, and disposal of large volumes of CKDs in uncovered and unlined piles that are

easily removed by wind and eroded by water (EPA, 1993). Due to the leachate and

fugitive dust concerns, standards and guidelines have been developed for management of

CKD stockpiles and landfills.

24

2.2 CKD and Portland Cement

A basic understanding of CKD compositions and variabilities is fundamental to any

investigation of their use. CKDs never contain just a single component and the range of

the components and fineness varies not only with the type of cement kiln operation, but

also with the raw materials. The chemical, mineralogical, and physical property

differences among CKDs and between CKDs and PC must be well understood in order to

understand the potential effects in concrete. CKDs are derived from the same raw

materials and pyroprocess as clinker. Since CKDs are only partially burnt (relative to

fully burnt clinker), CKD compositions differ from PC (Corish and Coleman, 1995). The

fineness of a CKD can also be a factor in its influence on concrete properties and is an

additional component to be considered.

2.2.1 Chemical Properties

Sreekrishnavilasam et al. (2006) summarized statistics on the chemical oxide

composition of CKDs based on 63 published datasets from different cement plants, as

shown in Table 2.5. The table presents a statistical analyses of the main oxides present in

CKDs as well as the total alkalis (based upon equivalent sodium molar mass), loss on

ignition (LOI), and free calcium oxide content (note: free calcium oxide content was not

available for all datasets).

The chemical composition of PC is usually given as oxides on a mass percent basis,

determined by various analytical tests, such as those in ASTM C114. PC has a typical

range for each of the four main oxides: CaO (60 – 66%), SiO2 (19 – 25%), Al2O3 (3 –

8%), and Fe2O3 (1 – 5%) (Taylor, 1997). There are five categories of PC in ASTM C150

with equivalent cement types in CSA: ASTM TI and CSA-GU (normal/general use),

ASTM TII and CSA-MS (moderate sulfate resistant), ASTM TIII and CSA-HE (high

early strength), ASTM TIV and CSA-LH (low heat of hydration), and ASTM TV and

CSA-HS (high sulfate resistant). In 2005, a survey of the 123 cement plants in North

America was conducted to determine the chemistry of the different categories of PC

25

manufactured in North America (Tennis and Bhatty, 2006). The data from the 92 cement

plants that responded is presented in Table 2.6. The free calcium oxide and chloride

contents for PC normally appear in minimal quantities and are therefore, not typically

reported. Lawrence (1998a) reported that 132 samples of PC had an average free lime

content of 1.24% in a range of 0.03 – 3.68%. PC chloride content is typically less than

0.01%. Tennis and Bhatty (2006) did not present data for TIV, as it is not produced in

significant amounts in North America.

Table 2.5 CKD chemical oxide composition, free lime, and loss on ignition, and

statistical analysis of 63 published datasets (Sreekrishnavilasam et al., 2006)

Chemical Composition, %

CaO SiO2 Al2O3 Fe2O3 MgO SO3 Na2O K2O

Equivalent Alkali %

fCaO & Ca(OH)2

%

Loss on Ignition

%

Average 43.99 15.05 6.75 2.23 1.64 6.02 0.69 4.00 3.32 6.75 21.57

Standard Deviation 8.01 4.74 7.83 1.04 0.68 3.93 1.02 3.01 2.44 7.83 8.50

COV (%) 18 31 116 47 41 65 147 75 74 116 39

Max. 61.28 34.30 27.18 6.00 3.50 17.40 6.25 15.30 11.42 27.18 42.39

Min. 19.4 2.16 0.00 0.24 0.54 0.02 0.00 0.11 0.14 0.00 4.20

COV (%) = Co-variance Equivalent Alkali: Na2O + 0.658 x K2O fCaO: free calcium oxide (free lime) Ca(OH)2: Calcium hydroxide

Table 2.6 Portland cement chemical oxide composition, total alkali content, and loss on

ignition (Tennis and Bhatty, 2006)

Chemical Composition, % Type of Portland Cement (ASTM)

CaO SiO2 Al2O3 Fe2O3 MgO SO3

Equivalent Alkali %

Loss on Ignition

%

TI Normal: Average 63.23 20.17 5.07 2.66 2.51 3.26 0.70 1.52

Standard Deviation 1.04 0.66 0.54 0.44 1.02 0.62 0.26 0.48

TII Moderate Sulfate Resistant: Average 63.66 20.85 4.62 3.32 1.98 2.91 0.56 1.39


TIII High Early Strength: Average 63.33 20.38 4.84 2.86 2.21 3.60 0.61 1.51


TV Sulfate Resistant: Average 63.85 21.61 3.80 3.87 2.18 2.34 0.45 1.29


Equivalent Alkali = Na2O + 0.658 x K2O

26

The data in Table 2.5 indicates that calcium and silica oxides are the major constituents

for CKDs, although these values are lower than what is found for PC in Table 2.6. Free

calcium hydroxide can sometimes appear as calcium hydroxide due to exposure to

moisture. The CKD combined free calcium oxide and calcium hydroxide contents and

LOI are significantly higher than in PC for this dataset. It is also observed that CKDs

generally contain higher concentrations of sulfates and total alkalis than PC. These

findings are not surprising since volatiles are preferentially drawn towards CKD in the

kiln pyroprocess. The alumina, iron, and magnesium concentrations of CKD and PC

appear to be similar. The CKDs tend to have higher concentrations of potassium than

sodium in this dataset, which is to be expected since there is usually a similar ratio for

cement raw materials in North America. Although not included in Table 2.5, chlorides

can appear in significant levels in CKDs. In an early study, Haynes and Kramer (1982)

reported that 113 CKD samples from 102 cement plants in the U.S had an average

chloride content of 0.71% with a range between less than 0.01% to as high as 12.3%.

Similar to other construction materials, PC and CKDs have a wide range of trace metals.

Trace metals reported in clinker and CKD analyses are normally present in quantities

small enough not to influence the performance of the cement (<0.05%) (Corish and

Coleman, 1995). Small quantities of trace metals only leach out of CKDs using vigorous

procedures such as the U.S. EPA toxicity characteristic leaching procedure (TCLP)

(Corish and Coleman, 1995).

2.2.2 Mineralogical Properties

The Portland Cement Association (Hawkins et al., 2004) compiled a mineralogy

summary table (Table 2.7) of 113 CKD samples from 102 cement plants in the U.S. by

X-ray diffraction using raw data from the research conducted by Haynes and Kramer

(1982). Of the 113 CKD samples, 106 had a calcite level greater than 30%, which

indicates that the majority of the CKDs were from wet or long-dry kilns (CKDs from

preheater and precalciner kilns generally have low calcite and high free lime levels).

27

Additional common minerals found in the 113 CKDs, although to a lesser degree than

calcite, were: free lime (CaO), anhydrite (CaSO4), quartz (SiO2), dolomite

((CaMg(CO3)2), mica, and feldspar. Other minerals found in only a number of the

samples were: aphthitalite ((K,Na)2SO4), arcanite (K2SO4), sylvite (KCl), portlandite

(Ca(OH)2), halite (NaCl), gypsum (CaSO4.2H2O), and chlorite

(Mg3(Si4O10)(OH)2.Mg3(OH)6). Althought it is reported that CKDs coming from zones of

high temperatures in wet and long-dry kilns often contain silicate compounds (i.e. C2S)

(Adaska et al., 1998), it is surprosing that Haynes and Kramer (1982) did not report the

presence of PC primary compounds in any of the CKDs.

Table 2.7 Mineralogical composition of U.S. CKD samples (Hawkins et al., 2004)

Alkali chlorides and alkali sulfates in CKDs are of particular interest as they tend to be

water soluble and enter solution in the early stages of hydration. Usually potassium is

more volatile than sodium in the kiln. The molar ratio of sulfate to water soluble alkalis

may indicate which sulfate phases are likely to be present in a CKD. Since chlorides are

not always present in the raw materials, very little is discussed in the literature regarding

alkali chloride formation in the pyroprocess. Due to the lower volatilization temperature

28

of chlorides as compared to sulfates, it is believed that chlorides will preferentially

combine with alkalis before sulfates (Lehoux, 2006).

The formation of the alkali sulfates depends upon the available amounts of the remaining

alkali and sulfate ions. Potassium and sulfur have a very high mutual affinity. Alkalis and

sulfate will preferentially form the double alkali sulfate, aphthitalite (3K2SO4.Na2SO4),

and/or the single alkali sulfate, arcanite (K2SO4). Arcanite will likely form if there are not

enough available sodium ions to produce aphthitalite. Thenardite (Na2SO4) will only

likely be present if the amount of sodium is greater than the amount of potassium in the

cement raw materials, which is rare in North America. In the cases where sulfate is

present in excess of the alkalis, the double salt known as calcium langbeinite

(2CaSO4.K2SO4) will likely form. If there is excess sulfate or a lack of potassium ions,

anhydrite (CaSO4) may also be present. Anhydrite, although water soluble, does not enter

solution as quickly as alkali sulfate compounds. There is no equivalent mineralogical

phase for sodium to mimic the potassium in calcium langbeinite (Bhatty, 2004).

The mineralogical composition of PC is most commonly determined using Bogue

equations that are described in North American Standards (ASTM C150, AASHTO M85,

CSA A3001). The data from the Tennis and Bhatty (2006) survey of the 123 cement

plants in North America for average Bogue compound composition and Blaine fineness

(surface area) of different PCs is presented in Table 2.8. The remaining 15% of PC

composition is the minor compounds that normally consist of gypsum (5%), limestone

(5%), magnesia (1%), the sodium equivalent alkali oxides (1%), and free calcium oxide

(1%).

29

Table 2.8 Portland cement average bogue compound and Blaine fineness in 2004 (Tennis

and Bhatty, 2006)

Type of Portland Cement (ASTM) C3S %

C2S %

C3A %

C4AF %

Blaine m2/kg

TI Normal Standard Deviation

56.9 4.57

14.8 3.71

8.9 1.81

8.2 1.37

384 19.3

TII Moderate Sulfate Resistant Standard Deviation

56.5 3.93

17.1 3.48

6.7 0.88

10.1 1.20

377 20.0

TIII High Early Strength Standard Deviation

56.2 4.13

16.2 3.91

7.8 2.14

8.8 1.80

556 55.5

TV Sulfate Resistant Standard Deviation

57.7 3.47

18.4 3.93

3.5 1.17

11.8 2.03

389 42.5

2.2.3 Physical Properties

Konsta-Gdoutos and Shah (2003) state that CKDs are generally off-white or light brown

in appearance. The limited number of research studies that provide fineness data typically

report Blaine fineness, relative density, and/or particle size distribution. The Blaine

fineness values of CKDs vary in the literature between 318 and 1400 m2/kg, which is

generally higher than the typical range of values for PC, as shown in Table 2.8.

Comparing the Blaine fineness values has led some researchers to conclude that CKDs

are finer than PC (Lachemi et al., 2008; Wang and Ramakrishnan, 1990; Ravindrarajah,

1982). The relative densities of CKDs have been reported to be typically between 2.6 and

2.8, which is closer to the density of raw material and less than the 3.15 relative density

typically assigned to PC (Konsta-Gdoutos and Shah, 2003).

PC consists of individual angular particles that are mostly (approximately 95%) smaller

than 45 µm. The average particle size of a PC particle is approximately 15 µm.

Peethamparan et al. (2008) presented the particle size distribution for four different fresh

CKDs and a Type I PC, as shown in Figure 2.5. CKD-1 (long-dry pyroprocess) and

CKD-2 (precalciner pyroprocess) had the finest and coarsest particle size distributions,

respectivley. CKD-3 (preheater/precalciner pyroprocess) and CKD-4 (wet pyroprocess)

had particle size distributions very similar to that of the Type I PC. CKD-3 and CKD-4

30

had a greater percentage of particles smaller than the PC up to between 10 and 20 µm,

but beyond 20 µm there was a smaller percentage of particles smaller than the PC. The

D50 values for the CKDs ranged between approximately 7.5 µm and 30 µm while the D50

value for the PC was approximately 15 µm.

Figure 2.5 CKD and PC particle size distribution (Peethamparan et al., 2008)

CKD Pyroprocess CKD 1: long-dry CKD 2: precalciner CKD 3: preheater/precalciner CKD 4: wet

31

Sreekrishnavilasam et al. (2006) presented the particle size distribution of five fresh

CKDs, one PC, two microcements, and one landfill CKD from previous studies, as

shown in Figure 2.6. The authors stated that the various CKDs show significant variation

in the mean particle size (D50 = 2.8 µm to 55 µm) as well as in the gradation (Cu = 5 to

25). Each CKD has a greater percentage of particles smaller than the PC between 0 and 8

µm. This shows that the CKDs contain more fine particles (smaller than 8 µm) than the

PC. Beyond 8 µm, however, the CKD particle size curves are on both sides of the PC

particle size curve.

Figure 2.6 CKD and PC particle size distribution from published literature

(Sreekrishnavilasam et al., 2006)

32

2.2.4 CKD Types

Inconsistency of any material can inhibit its use in construction applications. In realistic

terms, there is no typical or average CKD. The characteristics of CKDs vary from plant

to plant depending on the kiln feed composition, kiln design and operation, fuel type, and

the type of dust control systems (Hawkins et al., 2004). Therefore, a distinct CKD that is

used as a partial substitute of a PC at a given replacement level may perform differently

from another CKD that is used as a partial substitute of the same PC at an equivalent

replacement level.

The typical composition of CKDs covers a wide range of values as shown in Table 2.5

and Figure 2.6. Despite the fact that PC from cement plants across North America has

relatively little variation due to adherence to cement standard specifications, components

found in CKDs vary significantly. CKD composition differences among cement plants

are due to variations in raw materials, fuels, equipment design, and kiln operations.

As shown in Table 2.5, free calcium oxide content and LOI show large variation in

CKDs, although they only appear in minimal amounts in PC. Sreekrishnavilasam et al.

(2006) reported that the majority of CKDs in the literature studies have low free calcium

oxide contents (less than 5% free calcium oxide for 40 out of 43 samples). This implies

that the majority of CKDs in this sample set are from either wet or long-dry kilns. CKDs

from the wet and long-dry processes typically have much lower free calcium oxide (free

lime) and higher LOI than CKDs from the preheater/precalciner processes (Hawkins et

al., 2004). As preheater/precalciner pyroprocesses become more prominent in the cement

industry, the number of cement plants generating CKDs with free calcium oxide

concentrations greater than 20% will increase.

The concentration of volatiles in CKDs can be influenced by the type of fuel used in the

pyroprocess. Coal fuel has more sulfur than oil and gas fuels, which can increase the

concentration of volatiles in the pyroprocess. As well, oil and gas fuels tend to volatilize

33

more alkalis as compared to coal fuel. This is perhaps due, at least in part, to the higher

hydrogen levels in these fuels, which leads to higher water vapour concentrations in the

burning zone. Consequently, CKD from gas or oil fired kilns contain higher proportions

of soluble alkalis as compared to those from coal fired kilns (Klemm, 1980).

The variability of CKD particle size distributions can be largely attributed to differences

in dust collection systems and pyroprocess technologies. Some dust collection systems

are able to separate the fine CKDs from the total CKDs. There are often significant

chemical differences between total and separated CKDs, with the finer CKDs usually

having higher concentrations of volatiles and a lower free calcium oxide content (Collins

and Emery, 1983). CKDs from the bypass of precalciner kilns have also been described

to be coarser than CKDs from wet and long-dry kilns (Klemm, 1980).

Bhatty (1984, 1985a, 1985b, 1986) is the only researcher that has studied CKD-PC

interaction to categorize CKDs according to their compositions. The CKD classification

system used by Bhatty (1985b) was (i) low alkali-low chloride-low sulfate; (ii) low

alkali-low chloride-high sulfate; (iii) moderate alkali-low chloride-moderate sulfate; and

(iv) high alkali-high chloride-low sulfate. This illustrates the necessity to differentiate

CKDs according to their composition in considering their potential impact on cement

properties.

34

2.2.5 Variability of CKD from a Single Plant

The composition of CKDs not only varies between different cement plants, but CKD can

also vary from batch to batch within the same plant (Wang and Ramakrishnan, 1990). It

is very difficult to produce a homogenous CKD from the pyroprocess and cement plants

do not attempt to do so since a large portion is destined for landfills. Table 2.9 presents

summarized statistics on the CKD chemical oxide composition of intermittent daily

samples collected from a single kiln (long-dry process) over a 3-year period. Although

more variable than PC, the CKDs from a specific cement plant will generally have

considerably less compositional variation than the CKDs given in Table 2.5, which are

from a wide variety of sources (Corish and Coleman, 1995). As an example, the CKD

standard deviation of SO3 content from the single long-dry process plant is 1.53%, while

that from a wide variety of sources is 3.93%.

Table 2.9 CKD oxide composition and statistical analysis of intermittent daily samples

collected from a single kiln (long-dry process) over a 3 year period (2005 – 2008) in

North America (Lafarge, 2009)

Component SiO2 Al2O3 Fe2O3 CaO SO3 MgO K2O Na2O TiO2 P2O5 SrO Mn2O3 Cl

Average 14.91 4.11 1.43 43.86 5.78 1.20 2.59 0.13 0.20 0.05 0.06 0.06 0.43

Standard Deviation

0.91 0.24 0.13 2.61 1.53 0.22 0.67 0.04 0.01 0.00 0.01 0.01 0.15

No. of samples

565 565 565 565 565 565 565 565 565 565 565 565 565

As knowledge regarding the use of CKDs in concrete improves, the cement industry may

look to invest in the systems and resources that will be required to produce CKDs with

less variability from an individual cement plant. CKDs that will be used as a partial

replacement of PC must be handled in a fashion that is similar to conventional PC to

ensure a consistent and high quality product (sampling ports for quality monitoring,

metering systems, pneumatic handling systems, and silos for storage).

35

2.3 Portland Cement Hydration

Any study on the use of CKDs as a partial replacement of PC first requires an

understanding of PC hydration. C3S and C2S both react with water to form calcium

silicate hydrate (C-S-H) and calcium hydroxide (CH) (also known as portlandite). The C-

S-H provides most of the strength developed by PC. C3S hydration occurs more rapidly

than C2S hydration. Therefore, C3S provides most of the early age strength while C2S

contributes mostly to the later age strength (Gartner et al., 2002).

The reaction between PC and water is mostly an exothermic reaction that takes place in a

sequence of stages. Traditionally, isothermal conduction calorimetry has been used to

follow the progression of hydration by monitoring the rate of heat liberation of the

cement paste. Most researchers have identified five stages of PC hydration. A typical

isothermal conduction calorimetric curve for a Type I PC is shown in Figure 2.7 with the

stages of hydration indicated as: (1) initial reaction, (2) induction, (3) acceleration, (4)

deceleration, and (5) slow continued reaction (Taylor, 1997). The main hydration peak

occurs during stages 3 and 4 and is associated with C3S hydration that produces C-S-H,

the main component that contributes to PC paste strength. The intensity and location of

the sulfate depletion peak, characterized by the formation of monosulfate during stages 4

and 5, are normally dependent on the amount of C3A and sulfate in the cement (Tennis

and Kosmatka, 2004). A representation of the relative volumes of the major compounds

in the microstructure of hydrating PC pastes as a function of time is shown in Figure 2.8.

36

Figure 2.7 Heat evolution of PC paste during hydration stages: (1) initial reaction, (2)

induction, (3) acceleration, (4) deceleration, and (5) slow continued reaction (Gartner et

al., 2002)

Figure 2.8 Relative volumes of the major compounds in the microstructure of hydrating

PC pastes as a function of time (Odler, 1998)

C

2

3

4

5

37

It is widely accepted that gypsum is added to PC to control the reaction of C3A. Most

researchers believe that this allows the setting and hardening to be controlled by the C3S

and water reaction (Gartner et al., 2002). Gypsum and alkali sulfates provide readily

soluble sulfate that surrounds the C3A and forms ettringite (C3A.3CaSO4.H2O32). There

are other ions that can partially or completely replace sulfate, whereas iron and silica may

substitute for alumina. Therefore, ettringite in cement paste should be indicated by the

more general AFt (Gartner et al., 2002). The AFt continues to form if sufficient sulfate

ions are present in the solution. Once the sulfate is depleted, the remaining C3A reacts

with the AFt to form monosulphates (AFm). The hydration of the C4AF forms hydration

products similar to C3A, both with and without gypsum (Gartner et al., 2002). Without

the presence of calcium and sulfate ions, the C3A reacts very rapidly with water to

produce calcium aluminate hydrates, such as C3AH6. The formation of calcium aluminate

hydrates at this stage is undesirable as they may cause rapid setting of the PC as a whole

(flash set).

Many factors other than the four major components of PC can impact cement paste,

mortar, and concrete properties. Besides the clinker composition, the presence of minor

oxides may also affect the resultant cement strength. For example, the uptake of elements

(i.e., sulfate or alkali) in the C-S-H formation can occur during hydration of C3S (Taylor,

1997).

2.3.1 Initial Hydrolysis

The first stage of PC hydration is initial hydrolysis. As soon as PC contacts water, an

initial heat peak occurs that mainly involves C3A, C4AF, alkali sulfates, free lime, and

calcium sulfates. The C3A and C4AF first react very rapidly and exothermally, which

results in the contribution of calcium and aluminate ions into solution. Iron is not

typically soluble. The aluminate concentration then reduces within seconds due to the

precipitation of AFt, which forms a layer over the cement particles. Alkali sulfates,

hemihydrates, and gypsum provide the readily soluble sulfates which contribute to AFt

38

formation at this stage. Free lime usually dissolves rapidly and exothermally but the

amount varies widely depending upon its reactivity. Reactive free lime in sufficient

amounts can lead to portlandite supersaturation (Gartner et al., 2002).

The dissolution of alkali sulfates is very rapid and endothermic. The alkalis enter into

solution and reach constant concentration within one minute of hydration. In order to

balance the cations and anions in solution as SO3 begins to combine with other elements

to form AFt, the alkali sulfates are replaced by alkali hydroxides which rapidly increase

the pH of the solution. Dissolution of calcium sulfate proceeds more slowly (relatively

modest amounts dissolve within the first few minutes of hydration) and is mildly

exothermic. The rate and amount of calcium sulfate dissolution is affected by its form.

At normal temperatures, hemihydrate is the most soluble form of calcium sulfate,

dihydrate is less soluble, and anhydrite is the least soluble. PCs that contain high levels of

metastable sulfates – such as hemihydrate and calcium langbeinite – often react to form

the precipitate phases gypsum and/or syngenite. These phases can lead to observable

changes in workability (Gartner et al., 2002).

2.3.2 Induction

The second stage of PC hydration is a period of reduced heat evolution after the initial

reaction. The lack of heat evolution, however, does not mean there is nothing occurring.

The slow formation of early C-S-H and AFt leads to an increase in viscosity. The causes

of the induction period and its termination have been the subject of many studies (Taylor,

1997). Many of these studies have used the hydration of C3S as a model for the hydration

of PC. Although there has been much debate, Taylor (1997) stated that the balance of the

evidence favours a combination of two hypotheses for the cause and end of induction.

The first hypothesis is that the induction phase causes the formation of a protective layer

on the C3S particles, the induction phase ending when this layer is destroyed or rendered

more permeable by aging or phase transformation. The second hypothesis states that the

39

rate of reaction in the induction phase is controlled by nucleation and growth of the C-S-

H formed in the main reaction; the induction period ends when C-S-H growth begins.

The termination of the induction period coincides with crystallization of calcium

hydroxide. The length of the induction period seems to depend upon how quickly the

calcium concentration rises to reach the maximum calcium hydroxide supersaturation.

This supports the idea that a certain minimum calcium hydroxide concentration is

required for the onset of the acceleration stage (Gartner et al., 2002). Setting does not

occur during the induction phase unless abnormal setting occurs. Flash set is a common

form of abnormal setting and occurs when there is an inadequate supply of calcium and

sulfate ions to react with the C3A, which results in the early formation of

monosulfoaluminate (AFm) phases. False set, another common form of abnormal setting,

most commonly occurs when there is an excess of sulfate in the liquid phase leading to

secondary gypsum formation. A false set paste can be re-mixed to regain its plastic form,

while a flash set paste cannot.

2.3.3 Acceleration

The acceleration phase of PC typically represents the change from a plastic to rigid

consistency (initial and final set) and early strength development. Initial set, as defined in

ASTM C150, is the time it takes for the depth of penetration of a needle in paste to be

less than 25 mm within 30 seconds. Setting is the formation of a network of partially

hydrated cement particles connected by PC hydration products (Nonat, 1994). Therefore,

as the water to solid ratio increases, the setting times will also increase. It is generally

accepted that initial setting is controlled by the hydration of C3S. Under normal

conditions, initial set and the transition from the induction phase to the acceleration phase

are reported to be correlated. The termination of induction will typically not correlate

with pastes that undergo abnormal setting (false or flash) since very little heat is evolved

during false set. It is important to note that the termination of induction and the beginning

40

of the acceleration are not always well-defined (Gartner et al., 2002). Final setting, as

defined in ASTM C150, normally occurs near the mid-point of the acceleration phase.

There is a high rate of heat evolution during this phase. The acceleration phase of C3S

hydration performs very similarly to the acceleration phase of PC. In both instances, the

main reaction is the formation of C-S-H and portlandite. It is generally accepted that the

rate of hydration in the acceleratory period is controlled by the nucleation and growth of

C-S-H. The rapid formation of hydrates leads to solidification and a decrease in porosity.

Sulfates, and possibly other ions, are significantly adsorbed and/or entrapped by C-S-H

(Gartner et al., 2002). The major heat peak of the PC hydration curve occurs at the end of

acceleration (Taylor, 1997).

2.3.4 Deceleration

The rate of C-S-H formation and portlandite decreases during the deceleration phase.

This results in reduced rate of heat evolution. There is general agreement that the main

reaction (C3S hydration) makes a transition from chemical control to diffusion control

sometime prior to the acceleration peak and continues in the deceleration phase. This is

likely due to the precipitation of hydrates surrounding the C3S particles, although the

form of the diffusion barrier is not clear (Gartner et al., 2002).

The sulfate in the liquid solution begins to decline due to continued formation of AFt as

well as uptake by the C-S-H. The sulfate depletion typically occurs between 12 and 36

hours and is indicated by a small peak during deceleration. At the time of sulfate

depletion there is a conversion of AFt formation to AFm formation. If there is an excess

amount of sulfate in the liquid phase and depletion does not occur, AFt will continue to

form until C3A is depleted.

41

2.3.5 Slow Continued Reaction

The continuous strength gain and reduction in porosity of paste, mortar, and concrete

occurs during the slow continued reaction phase, but at a continually decreasing rate.

Beyond one day, the only ions in solution above concentrations of a few mmol/l are

potassium, sodium, and hydroxyl ions. The concentrations of these ions tend to rise

slightly approaching a limit after about 28 to 90 days, primarily due to consumption of

the fluid phase (from ongoing hydration) (Taylor, 1997). Although the strength and

porosity development are important to the long term performance and durability of

concrete, hydration studies during this phase are limited (Mostafa and Brown, 2005).

2.4 Effects of CKD Properties and PC Dilution

The effects of different CKD-PC blends often provide conflicting and variable results,

due in large part to the compositional variability of CKD among different sources.

Although the effects of these components in combination and at varying replacement

levels are not well understood, there is considerable knowledge of the effects of each

individual component at varying replacement levels and dilution of PC. In an attempt to

understand the interaction of CKD-PC blends, it is important to appreciate how each

component of CKD replacement can individually influence hydration, performance, and

durability. In this way, it is possible to appreciate some of the potential effects of CKD. A

detailed explanation of the synergistic effects of a combination of the various components

within a CKD is beyond the scope of this literature review.

2.4.1 Calcium Carbonate

CKDs can consist of up to 50% calcium carbonate. Limestone is the most common form

of calcium carbonate in North America. The question of whether limestone additions

should be permissible has stimulated a great deal of debate and research. Various national

standards have adopted different positions. The European Standard (EN 197) allows up to

35% and North American Standards (CSA, ASTM, and AASHTO) allow up to 5%. CSA

will soon allow up to 15% limestone addition. The effects of the limestone as a partial

42

substitute of PC are both physical and chemical (Taylor, 1997). The chemical effects of

calcite will be discussed in this section. The physical effects of limestone addition are

covered in more detail in Section 2.4.10.

During normal PC hydration, C3A and calcium sulfate react to form AFt. Sulfate

depletion typically occurs before the C3A consumption is complete, resulting in the

conversion of AFt to AFm. The presence of calcium carbonate, however, alters these

reactions. First, AFt formation is accelerated in the presence of calcium carbonate

(Ramachandran and Zhang, 1986). Second, the conversion of AFt to AFm is delayed or

prevented due to the reaction between C3A and calcium carbonate to form calcium

carboaluminates. The formation of calium carboaluminates occurs as some of the sulfate

ions are replaced by carbonate ions during C3A hydration (Vernet and Noworyta, 1992).

Bensted (1980) investigated the use of limestone for partial substitution of the gypsum to

control the early hydration of C3A. Although he concluded that sulfate ions are more

effective than carbonate ions, Bensted (1980) also stated that it is possible to substitute

limestone for up to 50% of the gypsum without a deleterious effect. This has been cited

for the optimum sulfate content decrease when limestone addition increases (Cochet and

Sorrentino, 1993). The importance of the reactivity between C3A and calcium carbonate

additions is highlighted by reports that carbonate additions with sulfate resistant cement

(low C3A) act primarily as an inert diluent (Klemm and Adams, 1990).

Calcium carbonate additions also influence the hydration of C3S. Taylor (1997) stated

that the accelerating effect of carbonates in suitable concentrations appears to be confined

to the initial stage of reaction. The accelerating effect occurs with pure C3S as well as

with PC and is, therefore, associated with the behaviour of that phase. Limestone

enhances the rate of formation of C-S-H and CH, probably because it offers nucleation

sites for growth. Ramachandran (1988), however, reported that calcium carbonate also

forms a complex with the hydrated products of C3S. More recently, Pera et al. (1999)

43

reported that hydration of C3S in the presence of CaCO3 produced calcium carbosilicate

hydrate.

Barker and Mathews (1989) reported on the heat evolution of limestone filler cements.

Their studies indicated that as the amount of limestone increased, the major heat peak and

total amount of heat released both decreased. The time that the major peak appeared,

however, was dependent upon the method of limestone-PC blend preparation. Blending

the limestone with PC was shown to either have no effect or to retard the time of the

major peak, while intergrinding limestone and PC was shown to accelerate the time of the

major peak. Hooton (1990) determined the 7-day heat evolution (ASTM C186) for

commercially available PCs and limestone-PC blends made from the same clinkers. The

author reported that there was no consistent effect of limestone on the total heat of

hydration.

Sprung and Siebel (1991) reported reduced water demand with limestone filler cements

and attributed this to improved particle packing. Cochet and Sorrentino (1993) stated that

the water-reducing action of the fillers is greater for a water to cement ratio (w/c) of less

than 0.4, but this effect is dependent upon the quality of the limestone. A limestone from

clay rock deposits or soft and porous rock leads to an increase in the water demand and

reduces the positive effects of a limestone, discussed in further detail in Section 2.4.3.

Researchers have observed that the setting times are marginally reduced as the limestone

additions increase (Brookbanks, 1989; Vuk et al., 2001).

Hawkins et al. (2005) assessed the compressive strength data for mortars and concrete

made with and without limestone as being up to 6% in PC from various data sources.

This data analysis showed that up to 5% limestone addition can provide strengths similar

to PCs without limestone. Beyond the 5 – 10 % range of limestone addition to PC,

strengths are lower than for PC alone, due to the dilution effect. This effect can be offset

to an extent by grinding the limestone-PC blend finer (Sprung and Siebel, 1991).

44

The presence of calcium carbonate additions may increase the likelihood of thaumasite

(CaSiO3.CaCO3.CaSO4.15H2O) formation. Thaumasite formation occurs in cold and wet

environments by reaction of the C-S-H with sulfates and carbonate ions (Hooton and

Thomas, 2002). The thaumasite form of sulfate attack results in the decomposition of the

C-S-H and can completely destroy the binding capacity of the cement paste. The

conventional form of sulfate attack requires the involvement of C3A. Sulfate resistant

cement (low C3A), however, does not present any special protection from thauamsite

since the attack is in the silicate phase and not the aluminate phase. Although thaumasite

can cause severe damage, there are very few cases where it is the primary cause of

deterioration (Taylor, 1997).

2.4.2 Quartz

CKDs have been reported to contain up to 30% quartz. Quartz is inert (insoluble) and is

typically not found in PC. The partial replacement of PC with CKDs may have an impact

on cement properties due to the presence of unreactive raw materials within CKD. The

physical effects of quartz due to fineness (nucleation and filler effects) are discussed in

Section 2.4.10.

2.4.3 Clays

CKDs may contain clays or de-hydrated clays, although previous studies have not stated

this. PC generally does not contain clays, except those present in mineral additives such

as limestone. Since CKDs typically consist of partially decarbonated limestone, clays

may be present in CKDs. The presence of clay can lead to an increase in water demand

(Cochet and Sorrentio, 1993). The effect on hardened concrete is deleterious to freezing

and thawing resistance (Detwiler et al., 1996). Unreacted clay minerals could cause

problems in hardened concrete if they swell when exposed to water. There is also a

potential for an increase in sorption of certain cations, and no hydration products are

generated by clays in the presence of PC (Mattus and Gilliam, 1994). However, heat-

45

treated clays, such as metakaolin, can be pozzolanic. The pozzolanic reaction occurs in

the presence of calcium hydroxide and silica from the pozzolan to produce C-S-H, the

main PC hydrate that contributes to strength in concrete.

2.4.4 Free Lime and Calcium Hydroxide

CKDs generally have higher free limes than PC and have been reported to contain up to

40% free calcium oxide (free lime). A small portion of the free lime in CKDs is

sometimes found in the form of calcium hydroxide due to exposure to moisture.

Approximately 1.5% or less free lime is generally an advisable quantity for a given PC

(Bensted, 1983a). Free lime (uncombined lime) appears in the form of calcium oxide

(CaO) in clinker and is typically considered hard burnt. In PC, however, the addition of

damp gypsum and use of water spray to control temperature in the grinding mill can

hydrate some or all of the free lime to form calcium hydroxide. A large amount of the

hard burnt lime is not very reactive chemically towards water, but sufficient calcium and

hydroxyl ions are available in the solution phase during PC hydration to enable the

various chemical reactions that are influenced by calcium hydroxide to occur (Bensted,

1983a).

The calcium hydroxide formed by the hydration of C3S and that formed by hydration of

free lime are slightly different. The hydration of free lime to calcium hydroxide produces

poorly developed crystals that have a lower decomposition temperature using thermal

analytical methods such as thermal gravimetric analysis (TGA), differential scanning

conduction calorimetry (DSC), or differential thermal analysis (DTA) (Bye, 1999).

The hydration activity of free lime formed at different decarbonation temperatures is

variable. The rate of heat evolution of pure free calcium oxide decreases with increase of

firing temperature, as shown in Figure 2.9. The difference in microstructure of free

calcium oxide fired at various temperatures results in its different hydration activity.

When calcium carbonate initially decomposes at approximately 900˚C (Soroka, 1979),

46

the free lime retains its rhombohedral structure of calcite and the crystallite size is small.

It is known that reactive free lime (soft burnt lime) can significantly affect the rheological

properties of the CKD-PC mixture due to its high affinity for water molecules. With the

rise of decarbonation temperature, the crystals of free calcium oxide grow and change to

the cubic structure. Industrial free calcium oxide contains small amounts of SiO2, Al2O3,

Fe2O3, and other oxides and, consequently, the hydration reactivity is lower than that of

pure free calcium oxide (Shi et al., 2002).

Figure 2.9 Effect of firing temperature on the heat evolution of pure free calcium oxide

during hydration (Shi et al., 2002)

47

Gartner et al. (2002) has stated that the presence of free calcium oxide can enhance AFt

expansions. It appears that the formation of AFt in the presence of a deficiency of free

calcium oxide develops more blocky crystal with much less expansion and can rapidly

develop a strong matrix. The presence of calcium hydroxide has been reported to enhance

the ability of gypsum to retard the hydration of C3A (Collepardi et al., 1978; Brown et al.,

1984). The delayed formation of AFt and subsequent conversion to AFm has been

attributed to the development of a more effective AFt diffusion barrier.

Lime has an important role to play in the initial hydration of PC by supplying calcium

ions to the system. Nonat (1994) stated that the lime concentration is the most important

parameter during C3S hydration that determines thermodynamic, kinetic, morphological,

and structural formations of C-S-H. Therefore, any change in lime concentration or

displacement of the solubility equilibrium of portlandite – such as the addition of calcium

salts or alkalis – may change the formation characteristics of C-S-H. Nonat (1994) also

reported that the lime concentration in solution determines both the particle interactions

and solubility of hydrates that control the origin of setting. The duration of the induction

period, however, depends essentially on the number of nuclei of C-S-H precipitated from

the solution in its state of maximum supersaturation with respect to C-S-H. Therefore, the

lower the lime concentration, the greater the number of nuclei and, as a consequence, the

shorter the induction period (Damidot and Nonat, 1992). Since, under normal conditions,

initial set and the end of the induction period are reported to have a strong correlation

(Gartner et al., 2002), it is likely that an increase in lime concentration would retard the

induction period and, hence, the initial setting time. Nonat (1994) also reported that a

decrease in the w/b ratio of pastes mixed with saturated limewater shortened the

induction period due to the increase in the number of contacts between particles, even

though the number of initial nuclei is reduced due to a higher concentration of lime in

solution.

48

The free lime that reacts after cement has set will form calcium hydroxide. The volume of

calcium hydroxide is greater than the original free calcium oxide, which causes

expansion and damages the concrete internally. This type of expansion is called

unsoundness (Neville, 1996). Soundness cannot be predicted reliably from the free lime

content due to the varying hydration activity of free lime. Soundness issues related to free

lime reactivity occur after the paste is set, so it is likely that the hard burnt free lime at

high temperatures will cause soundness issues. Soft burnt lime hydrates rapidly before

the paste has set and, therefore, does not produce unsoundness.

2.4.5 Magnesia

The amount of magnesia oxide in CKDs is characteristically similar to that found in PC.

CSA A3001 and ASTM C150 limit the total magnesia content in PC to 6% by mass.

Magnesia is mostly present in the main silicate phases of PC, but some may be present as

crystalline magnesium oxide (periclase). Similar to free calcium oxide, the reactivity of

magnesia oxide depends upon the temperature at which thermal decomposition from

magnesium carbonate occurs. At lower temperatures of decomposition (700°C –

1000°C), the magnesia oxide may react with water prior to set, and thus not contribute to

expansion in the hardened state. The magnesia oxide in PC that has been exposed to high

burning temperatures will react with water slowly over a period of years to form

magnesium hydroxide and potentially cause expansion (unsoundness) in the hardened

paste (Soroka, 1979). Therefore, the amount of magnesia oxide in CKDs may not be a

good indicator of potential unsoundness. The effect of periclase on soundness is also

influenced by its particle size and distribution in clinker. Slow cooling of clinker allows

large periclase crystals to form such that when these hydrate slowly in concrete, the

expansion can cause unsoundness (Manias, 2004). Therefore, rapid cooling of clinker is

preferred for smaller and uniformly distributed periclase crystals that have less impact on

soundeness (Peray, 1986).

49

2.4.6 Sulfate

Most CKDs have higher levels of sulfate in comparison to PC. The sulfates found in

CKDs typically occur as single sulfates (K2SO4 and/or Na2SO4), apthitalite

(3K2SO4.Na2SO4), calcium langbeinite (2CaSO4.K2SO4), and/or anhydrite (CaSO4). The

sulfate phases often identified in CKDs are also commonly found in the clinker fraction

of PC. Gypsum, which is added to clinker during PC grinding, is the most important

source of sulfate in PC. During PC hydration, calcium and sulfate ions are supplied by

gypsum to control the reaction of C3A. Although CKDs do not typically contain gypsum,

they could provide readily soluble calcium ions (from free lime and calcium langbeinite)

and readily soluble sulfate ions from alkali sulfates during the early stages of hydration.

Therefore, the effects of alkalis and calcium in conjunction with sulfate must be

considered in this review.

It is generally accepted that the alkali sulfates and combined alkali/calcium sulfates are

rapidly (within minutes) dissolved upon hydration, whereas alkalis present in the

aluminate, ferrite, and silicate phases are released more slowly (perhaps even over

months or years). Sandberg and Roberts (2005) stated that the rate of solubility of the

different sulfate forms vary in the following order (highest to lowest rate of dissolution):

alkali sulfate and calcium langbeinite > plaster (calcium sulfate hemihydrates) > chemical

anhydrite (soluble calcium sulfate anhydrite) > gypsum (calcium sulfate dihydrate) >

syngenite > natural anhydrite.

The amount of gypsum addition to PC is very important. The supply of sulfate ions

controls the setting and maximizes the early strength development of cement. This

process is disturbed if the renewed hydration of C3A takes place early. Therefore, it is

desirable to suppress the C3A hydration with an appropriate amount of sulfate so that it

does not coincide with the C3S hydration. The optimum amount of sulfate in PC should

(i) retard C3A hydration, (ii) inhibit C3A hydration until C3S hydration takes place to

cause the setting of the cement, and (iii) not form an excessive amount of ettringite to

50

cause deleterious expansion after the cement has set and hardened (Bhattacharja, 1997).

Each PC is unique and the optimum amount of gypsum for set control as well as other

properties – such as early compressive strength – must be determined individually. It is

also important to note that the optimum amount of gypsum is not the same for all

performance parameters (Gartner et al., 2002).

Tang and Gartner (1988) reported that the presence of soluble sulfates strongly retards

initial C3A hydration. In addition, the chemical and physical form is very important. The

interblended mixed alkali/calcium sulfates (calcium langbeinite and syngenite) are more

effective retarders of C3A than either gypsum or pure alkali sulfates alone. The proposed

mechanism takes into account the rate at which the sulfate phases can supply both

calcium and sulfate ions to the surfaces of the aluminate phases during early stage

hydration. Tang and Gartner (1988) concluded that the use of alkali/calcium double salts

increases the rate and chemical potential at which calcium and sulfate ions enter the

solution. Single alkali sulfates (K2SO4 and Na2SO4) and apthitalite (3K2SO4.Na2SO4),

however, are generally not known to be effective retarders of C3A hydration.

Lawrence (1998b) examined the heat of hydration for a PC with different levels of

gypsum addition, shown in Figure 2.10. With 0.5% sulfate addition to the PC, the heat

evolution of the aluminate peak that was originally superimposed on the main silicate

hydration peak was retarded and weakened, and at 2.5% sulfate addition, the aluminate

hydration peak was suppressed. Lawrence (1998b) also observed that the main silicate

heat peak is depressed at calcium sulfate levels above optimum.

51

(a)

(b)

(c)

Figure 2.10 Heat of hydration of cement paste determined by isothermal conduction

calorimetry, (20°C and w/c = 0.44); (a) PC (b) PC + 0.5% SO3, (c) PC + 2.5% SO3

(Lawrence, 1998b) Note: Sulfate added as Gypsum (Calcium Sulfate)

52

As the amount of gypsum added to a PC increases, the setting time also increases until a

level of stability is reached and the setting time becomes insensitive to further additions

of gypsum (Frigione, 1983). The hydration of silicate phases is accelerated in the

presence of calcium sulfates (Ish-Shalom and Bentur, 1972). The effect of calcium sulfate

on compressive strength at various ages of a PC is shown in Figure 2.11. It is clear that

the optimum sulfate is different for the three ages of compressive strength. Soroka and

Relis (1983) stated that the optimum content in the compressive strength curve for PC at

a particular age implies that the addition of gypsum involves two opposing effects. The

lower range of sulfate content has a beneficial effect on strength and can be attributed to

the allowance of C3S to hydrate to a beneficial strength by controlling C3A hydration.

The range of sulfate greater than the optimum has an adverse effect on strength. Two

suggested mechanisms of excessive sulfate ions are: (i) excessive AFt formation and the

associated volume increase cause internal cracking of the hardened paste and (ii) C-S-H

formation is accelerated but has lower intrinsic strength due to incorporation of sulfate

ions into its structure. Both mechanisms may contribute to the phenomenon caused by

excessive calcium sulfate (Gartner et al., 2002).

Abnormal setting behaviour is usually related to chemical reactions involving aluminates

and sulfate phases (Gartner et al., 2002). False set generally occurs when there is too

much readily soluble sulfate, which can come from plaster and/or alkali sulfates. The

liquid phase becomes over-saturated with sulfate and precipitation as secondary gypsum

occurs. The crystals of gypsum are needle-shaped and weak, but can still restrict the

workability of the mix. It is called false set because upon re-mixing the needles will

break-up and the mix will revert to its original consistency. Although not commonly

reported, false set may also arise due to precipitation of syngenite or ettringite (Gartner et

al., 2002).

53

Figure 2.11 Optimization of gypsum additions for compressive strength at different ages

(Gartner et al., 2002) (Note: this PC required higher SO3 levels than normal to obtain

maximum strength)

54

Excessive sulfate in PC can also lead to expansion problems due to formation of AFt. The

reaction between C3A and calcium and sulfate ions to form AFt involves increases in the

volume of solids. When the appropriate amount of calcium sulfate (optimum sulfate) is

present in PC, AFt formation occurs when the paste is plastic and volume increases do

not impact the integrity of the paste. At higher levels of sulfate (i.e., greater than

optimum sulfate), however, the formation of AFt may take place in the hardened paste

and possibly cause expansion and/or cracking (Soroka and Relis, 1983).

2.4.7 Chloride

The range of chloride content in CKDs from previous studies is between 0 and 12%. PC,

however, generally has less than 0.01% chloride content. The American Concrete

Institute (ACI 318) guideline for maximum water soluble chloride ion (Cl-) in concrete,

as a percent by mass of cement, is limited to: 1% for reinforced concrete exposed to

neither a moist environment nor chlorides, 0.15% for reinforced concrete exposed to a

moist environment or chlorides or both, and 0.06% for prestressed concrete.

CKD chloride ions generally appear as alkali chlorides (NaCl and/or KCl). Alkali

chlorides are more soluble than alkali sulfates and will enter solution within minutes of

hydration. Although calcium chloride in CKDs is rare, it is important to consider its

effects as well as those of alkali chlorides. Calcium ions could be present during the early

stages of hydration due to the presence of calcium-bearing phases that are readily soluble.

Therefore, the effects of alkali and calcium ions in conjunction with chloride ions are also

considered in this review. Bhatty (1984) also suggested that the alkali chlorides in CKDs

would probably behave similarly to calcium chloride.

Calcium chloride is a highly soluble salt that releases calcium and chloride ions into

solution and has long been used to shorten both the setting and hardening time of

concrete by accelerating the hydration reactions. Calcium chloride is one of the most

effective accelerators of PC pastes but the mechanism is not well understood. A practical

55

dosage is typically between 1 and 2%, by mass of cement, and its acceleration effects

increase as the concentration of calcium chloride increases (Juenger et al., 2005).

Potassium chloride (KCl) and sodium chloride (NaCl) are less effective accelerators than

calcium chloride. At very high concentrations, some salts (such as NaCl) act as retarders

of C3S (Taylor, 1997). Calcium ions are considerably more effective than any other

cation in salts used for accelerating hydration, suggesting that a specific effect is

superimposed on a general one (Taylor, 1997).

It is well known that the chemical binding of chlorides is influenced by the amount of

aluminate phases. C3A can react with chlorides to form calcium chloroaluminate hydrate

or Friedel’s salt (Taylor, 1990). The presence of sulfate ions in the binder, however,

reduces the chloride binding capacity of cement. Holden et al. (1983) attributed the

reduction in the chloride binding capacity to the preferential reaction of sulfate ions with

the C3A phase forming AFt. It is generally accepted that chlorides react with C3A only

after AFt formation is complete and sulfate depletion occurs (Taylor, 1997).

The effect of calcium chloride on PC heat evolution is shown in Figure 2.12. The

accelerated hydration of PC is indicated by a higher heat liberated at the major peak, the

shift of the major peak to the left side, and a narrower curve around the major peak. Early

strengths will tend to be higher but the final strengths will be reduced. Shoaib (2002)

also stated that the larger amounts of chloride present in CKDs can cause a sort of

crystallization of hydration products. The crystallization results in opening the pore

system within the hardened samples leading to a reduction in strength. It is well accepted

that the acceleration of PC hydration with calcium chloride is mostly due to an

acceleration of C-S-H growth. The presence of chlorides is typically associated with

higher early strengths (1 and 3 days) and lower later strengths (beyond 28 days). Despite

a significant amount of effort to understand the acceleration effect of chloride on PC

hydration, however, the detailed mechanism still remains unclear.

56

Figure 2.12 Effect of calcium chloride on heat development in PC (Lerch, 1944)

The presence of chlorides is a durability concern for steel reinforced concrete. The

chlorides that are not bound or that leach from the bound hydrates can contribute to steel

corrosion. The corrosion of steel in concrete is an electrochemical process and it is a

consequence of this corrosion that the surrounding concrete is damaged (Neville, 1983).

57

2.4.8 Alkalis

The CKD equivalent alkali contents (Na2O + 0.658 x K2O) from previous studies range

between 0.14 and 11.42%. The equivalent alkali content of PC is typically lower

(between 0.5 and 1%). Alkali cations in PC typically occur either as sulfates or in the

major clinker phases. The balancing anion sooner or later enters a hydration product of

low solubility and an equivalent amount of hydroxyl ion is released (Taylor, 1997).

Alkalis (potassium and sodium) in CKD that can greatly impact PC hydration normally

occur as readily soluble alkali sulfates and/or alkali chlorides. CKD alkalis can also occur

in less soluble form within other mineralogical phases.

In general, soluble alkalis are reported to accelerate hydration at an early age, which is

attributed to an increase in the permeability of the layer of hydration product surrounding

the alite grains after the reaction has become diffusion controlled (Neville 1983). Set time

may shorten due to the increased C3S hydration. It is widely reported that increasing

alkali content generally increases early strength (1 and 3 days) and decreases late strength

(28 day). However, these effects are modified by the gypsum content of PC. Osbaeck and

Jons (1980) reported that the alkali effects on strength are diminished or absent at

gypsum contents above the optimum sulfate level. Further, Jackson (1998) stated that

when alkalis are present as calcium langbeinite (2CaSO4.K2SO4), a reduction in early

strength and an increase of the same magnitude of strength at 28 days would not, relative

to a PC with less alkali sulfate, be unexpected.

Excess soluble potassium is widely known to precipitate syngenite which may lead to

early stiffening and false set. The presence of soluble alkalis can also impact the rate of

gypsum consumption and, thus, affects the levels of calcium and sulfate in solution. It has

been reported that the optimum gypsum content increases as the alkali content increases.

Calcium salts and alkali hydroxides that are both soluble can influence initial dissolution

of C3S due to the common ion effect (Gartner et al., 2002).

58

Increased alkali content in concrete presents durability concerns (Taylor, 1997). ASR is a

reaction between hydroxyl ions and certain forms of silica in aggregate to form ASR gel.

ASR gel formation causes durability problems that arise as a result of tensile cracks in

concrete. The presence of soluble alkalis can also influence air entrainment in fresh

concrete (Greening, 1967). Although the exact nature of this influence has not been

determined, it is believed that both the air content and the average size of the air voids

tend to increase with the amount of soluble alkalis. This can have an adverse effect on

freezing and thawing resistance.

2.4.9 Clinker Phases

CKDs can contain some or all of the four major clinker phases. Any changes in the

amount of C3A could impact the optimum sulfate balance. Due to the reduced amount of

silicates typically found in CKDs relative to PC and assuming all other parameters being

equal, the CKD strength gain contribution will be less than the contribution from the

replaced PC.


The effect of CKDs as partial replacement of PC can be influenced by the CKD physical

properties. The overall particle size distribution of PC and CKDs is called “fineness.”

CKDs may tend to have more fine particles than PCs below 8 µm (Section 2.2.3). The

densities of CKDs are generally lower than the PC industry standard of 3.15 (Konsta-

Gdoutos and Shah, 2003). Consequently, when CKDs are used as a partial replacement of

PC by mass, more CKD particles are required to replace the PC, which may affect

rheological properties. The fineness of a CKD will likely affect its chemical reactivity,

ability to act as a filler material (providing nucleation sites for hydration), and soundness

as a partial replacement of PC.

59

There is a strong correlation between fineness of PCs and water demand, as shown in

Figure 2.13. As the Blaine fineness (specific surface area) of a PC increases, the water

demand also increases, which is likely in part related to increased chemical reactivity

during the early stages of PC hydration. Increased Blaine fineness of a CKD may allow it

to have more impact on early age hydration in a CKD-PC blend by means of increased

ion dissolution. Therefore, a CKD-PC binder that has increased chemical reactivity

during early stages of hydration in comparison to the PC alone may also have a higher

water demand.

Figure 2.13 Relationship between water demand and specific surface area of PC (Sprung

et al., 1985)

CKDs may also contain significant amounts of calcite and quartz, which are both widely

known to be fillers (although it is recognized that limestone does chemically react with

aluminate phases to form carboaluminates). The presence of fine calcite and quartz

particles generally accelerates early PC hydration (Taylor, 1997). Greater fineness of the

CKD filler components could increase the hydration rate of the CKD-PC binder, most

likely by an increased surface area that also increases the number of active sites for the

60

nucleation of PC hydration products (nucleation effect). Alternatively, CKDs may

contain fine calcium carbonate particles that could fill the gaps between the cement

particles; improved particle packing of very fine filler has been attributed to reductions in

water demand as well as higher compressive strengths (Hawkins et al., 2005; Sprung and

Siebel, 1991).

The fineness or specific surface of the PC is one of the factors that influence the

autoclave expansion soundness assessment. If all other parameters of a PC are equal,

coarser ground cements have always exhibited a greater amount of autoclave expansion

(Klemm, 2005). Narang et al. (1981) quantified the effects of PC fineness on autoclave

expansion using a high MgO content PC. The PC was initially ground to a fineness of

225 m2/kg and had an autoclave expansion of 7.06%. When the same PC was ground to a

higher fineness of 350 m2/kg, the autoclave expansion was reduced to 1.39%. At an even

higher fineness of 400 m2/kg, the autoclave expansion was reduced to 0.24%.

Consequently, a reduction in fineness of a CKD-PC blend in comparison to the PC alone

may have an adverse effect on the soundness.

2.5 CKD-PC

The study of CKDs as a partial replacement of PC has been an intermittent research area

for the past 30 years. A list of the CKD-PC interaction studies, the number of CKD and

PC used, CKD replacement levels of PC investigated, the type of specimens used (paste,

mortar, and concrete), and the recommended limit of CKD replacement of PC for each

study are summarized in Table 2.10. Although these studies have shown that CKDs can

be used as a partial replacement of PC in the range of 5% to 15%, very little is known

about their exact role in cement paste, mortar, and concrete performance. The studies that

have been published on the use of CKDs as a partial substitute for PC often report

conflicting effects and mechanisms.

61

This section summarizes the materials, test methods, results, and conclusions of CKD-PC

interaction studies conducted over the past 30 years. Performance tests and properties for

CKD–PC blends – such as workability and water demand, setting time, hydration,

compressive strength, tensile and flexural strength, volume stability, and durability – are

presented. In order to focus on understanding the interaction between CKD and PC, the

literature review only considers studies of binary mixes.

Table 2.10 Summary of previous CKD-PC studies from literature review

Author # of

CKD # of PC

% CKD Replacement Tested P / M / C

Maximum % CKD Replacement

Recommended

Maslehuddin et al. (2008b) 1 2 0, 5, 10, 15 C 5%

Maslehuddin et al. (2008a) 1 1 0, 5, 10 P, M 10%

El-Aleem et al. (2005) 1 1 0, 2, 4, 6, 8, 10 P, M 6%

Al-Harthy et al. (2003) 1 1 0, 5, 10, 15, 20, 25, 30 M, C 5%

Udoeyo and Hyee (2002) 1 1 0, 20, 40, 60, 80 C N.R.

Wang et al. (2002) 1 1 0, 15, 25, 50 P, M 15%

Konsta-Gdoutos et al. (2001) 1 1 0, 15, 25 M 15%

Shoaib et al.(2000) 1 1 0, 10, 20, 30, 40 C <10%

Dyer et al. (1999) 2 1 0, 20, 35, 50, 75 P, M N.R.

Batis et al. (1996) 2 1 0, 6 C 6%

El-Sayed et al. (1991) 1 1 0, 3, 4, 5, 6, 7, 10 P, M 5%

Wang and Ramakrishnan (1990) 1 1 0, 5 P, M, C 5%

Ramakrishnan and Balaguru (1987) 1 3 0, 5 C 5%

Ramakrishnan (1986) 1 1 0, 5 P, M, C 5%

Bhatty (1986) 3 1 0, 10 M N.R.

Bhatty (1985b) 4 4 0, 10, 15, 20 P N.R.

Bhatty (1985a) 3 1 0, 10, 20 M N.R.

Bhatty (1984) 5 5 0, 10, 15, 20 P N.R.

Ravindrarajah (1982)

1

1

0, 25, 50, 75, 100 (P) 0, 15, 25, 35, 45 (C)

P, C

15%

CKD = Cement Kiln Dust; PC = Portland Cement P = Paste; M= Mortar; C = Concrete N.R. = Not Reported

62

2.5.1 CKD-PC Material Characterization

To effectively assess the effects of CKD as well as its reaction mechanisms involved as a

partial substitution of PC, it is essential to take into account the physical, chemical, and

mineralogical properties of both CKD and PC. The impact of CKD in a binary mixture

may be affected not only by the characteristics of the kiln dust, but also by the

characteristics of the cement.

The composition of CKDs that are removed from the pyroprocess is dependent upon the

raw material, fuel, kiln pyro-process, dust collection system, and type of cement being

produced. As a result, the composition of CKDs varies with respect to chemical

composition, particulate size, and mineralogy. Although there are variations among the

CKDs produced by different pyroprocesses and even within the same pyroprocess, there

are also similarities across all types of CKDs. All CKDs are a particulate mixture of

partially calcined and unreacted raw feed, clinker dust, and ash enriched with alkali

sulfates and other volatiles. All CKDs are also small enough to be carried by the

pyroprocess exhaust gases (Hawkins et al., 2004).

2.5.1.1 CKD-PC Chemical Composition

Bhatty (1984, 1985a, 1985b, 1986), one of the earliest published researchers to study

CKDs as a partial replacement of PC, stated that the chemical components of CKDs that

can affect cement/mortar/concrete properties are sulfates, alkalis, chlorides, free lime, and

calcium carbonate (CKDs typically contain higher concentrations of these chemical

components than PC). The chemical composition of the CKDs and PC used in each

CKD-PC interaction study over the past 30 years are presented in Table 2.11 and Table

2.12, respectively.

63

Very few researchers have characterized the complete chemical composition of the

CKD(s) used in their CKD-PC research study. From Table 2.11, it can be observed that

the CKD chemical components Bhatty (1985a) identified as affecting

cement/mortar/concrete properties are rarely reported; this is likely due to analyzing the

CKDs with the same procedures as for PC. For the chemical components that have been

reported, it is clear that the CKDs from different research studies, and even within the

same study, vary significantly. CKD chemical composition variabilities are heavily

influenced by variabilities in raw feed, fuel type, kiln process type, and product

specifications for the PC produced (Konsta-Gdoutos and Shah, 2003).

Table 2.12 shows the chemical composition of the PC that was used in each previous

research study to assess the use of CKDs as a partial substitute. The majority of the

previous research studies utilized TI cements. PC’s other than TI cement (PC 2, PC 12,

PC 13, and PC 14) were excluded from the statistical analyses in Table 2.12.

The chemical variability of the TI cements is considerably lower than that of the CKDs.

Since it is one of the volatile components, chloride (Cl) is not typically present in PC

(generally less than 0.01%) and, therefore, not reported. Typically the concentrations of

free lime (fCaO) in PC are low (typically less than 1.5%). Both chloride and free lime,

however, have a wide variation in CKDs. For the CKD free lime values reported, the

literature review does not cover the full range of free lime found in CKDs. The maximum

free lime reported in the literature review is 21.7%, whereas some CKDs have been tested

to contain as high as 35% free lime (Lafarge, 2005). The alkali (Na2O, K2O) and sulfate

(SO3) contents of the CKDs are generally higher in CKDs than in the TI cements. The

calcium oxide (CaO) and silica oxide (SiO2) contents of the CKD are generally lower

than in the TI cements, mainly as a consequence of partial decarbonation.

64

Table 2.11 Chemical and physical composition of CKD: from CKD-PC literature review

CaO SiO2 Al2O3 Fe2O3 MgO SO3 Na2O K2O Na2Oe Cl fCaO LOI Blaine

Author Material* % % % % % % % % % % % % m2/kg

Maslehuddin et al. (2008a and

2008b) CKD 1 49.3 17.1 4.24 2.89 1.14 3.56 3.84 2.18 5.27 6.9 N.R. 15.8 N.R.

El-Aleem et al. (2005) CKD 2 42.99 13.37 3.36 2.29 1.90 5.10 3.32 3.32 5.50 7.50 2.59 15.96 318

Al-Harthy et al. (2003) CKD 3 63.80 15.80 3.60 2.80 1.90 1.70 0.30 3.00 2.27 1.10 N.R. N.R. N.R.

Udoeyo and Hyee (2002) CKD 4 52.72 2.16 1.09 0.54 0.68 0.05 N.R. 0.11 0.33 N.R. N.R. 42.39 N.R.

Wang et.al. (2002)

Konsta-Gdoutos et al. (2001) CKD 5 56.99 17.67 5.06 2.75 0.91 6.55 0.30 3.43 2.56 0.38 N.R. 8.00 N.R.

Shoaib et al. (2000) CKD 6 49.75 11.95 1.12 2.45 1.86 6.35 3.87 2.66 5.62 6.80 N.R. 17.92 N.R.

Dyer et al. (1999) CKD 7 34.30 34.30 3.50 2.00 0.80 11.40 1.20 8.20 6.60 8.10 0.00 N.R. N.R.

Dyer et al. (1999) CKD 8 34.80 12.20 3.20 1.80 0.90 10.60 1.60 7.50 6.54 2.80 1.40 N.R. N.R.

Batis et al. (1996) CKD 9 43.95 10.12 4.07 2.89 0.95 0.27 0.18 0.82 0.72 0.38 N.R. N.R. N.R.

Batis et al. (1996) CKD 10 42.59 13.68 4.36 2.30 1.23 0.10 0.28 0.79 0.80 0.17 N.R. N.R. N.R.

El-Sayed et al. (1991) CKD 11 48.80 13.00 3.33 2.00 2.02 8.70 4.19 2.73 5.99 7.40 18.57 12.59 N.R.

Wang and Ramakrishnan

(1990) Ramakrishnan and Balaguru

(1987) CKD 12 45.71 15.78 3.95 1.09 0.98 2.32 N.R. N.R. N.R. N.R. N.R. N.R. N.R. Ramakrishnan

(1986)

Bhatty (1984-1986) CKD 13 49.30 14.70 3.31 2.04 1.03 3.07 0.23 2.60 1.94 0.24 10.43 23.43 511

Bhatty (1984-1986) CKD 14 51.70 15.50 3.84 2.13 1.59 11.10 0.22 2.50 1.87 0.26 21.72 10.50 489

Bhatty (1984-1986) CKD 15 41.90 15.40 2.65 1.51 1.35 0.25 0.23 4.90 3.45 3.47 3.00 34.06 439

Bhatty (1984, 1985b) CKD 16 41.70 14.00 2.85 1.51 2.73 5.55 0.27 3.60 2.64 0.29 4.31 27.81 566

Bhatty (1984) CKD 17 44.50 16.50 3.71 1.79 1.43 5.67 0.31 3.50 2.61 0.15 7.46 21.33 718

Ravindrarajah (1982) CKD 18 42.70 12.20 5.80 2.30 1.30 6.50 0.80 4.30 3.63 N.R. 6.10 22.10 528

#

samples 18 18 18 18 18 18 16 17 17 15 10 12 7

Average 46.53 14.75 3.50 2.06 1.37 4.94 1.32 3.30 3.43 3.06 7.56 20.99 510

St. Dev. 7.23 5.99 1.15 0.63 0.54 3.82 1.54 2.11 2.10 3.29 7.33 9.97 122

* CKDs are numbered as they are referred to in subsequent discussion N.R. = Not Reported; Na2Oe = 0.658 x K2O + Na2O fCaO = free calcium oxide (free lime) and calcium hydroxide LOI = Loss on Ignition

65

Table 2.12 Chemical and physical composition of PC: from CKD-PC literature review

CaO SiO2 Al2O3 Fe2O3 MgO SO3 Na2O K2O Na2Oe fCaO LOI Blaine Author Material* Type % % % % % % % % % % % m2/kg

Maslehuddin et al. (2008b) PC 1 TI 64.35 22.0 5.64 3.80 2.11 2.10 0.19 0.36 0.33 N.R. 0.7 N.R.

Maslehuddin et al. (2008b) PC 2 TV 64.07 20.52 4.08 4.24 2.21 1.96 0.21 0.31 0.41 N.R. 0.8 N.R.

Maslehuddin et al. (2008a) PC 3 TI N.R. N.R. N.R. N.R. N.R. N.R. N.R. N.R. N.R. N.R. N.R. N.R.

El-Aleem et al. (2005) PC 4 TI 64.00 21.06 5.43 3.41 0.75 2.48 0.10 0.12 0.18 0.22 2.42 300

Al-Harthy et al. (2003) PC 5 TI 62.50 20.60 4.50 3.60 2.60 2.70 0.20 0.50 0.53 N.R. N.R. N.R.

Udoeyo and Hyee (2002) PC 6 TI N.R. N.R. N.R. N.R. N.R. N.R. N.R. N.R. N.R. N.R. N.R. N.R.

Wang et. al. (2002)

Konsta-Gdoutos et al. (2001) PC 7 TI 64.29 20.35 5.24 3.58 1.13 2.56 0.11 0.60 0.50 N.R. 1.10 N.R.

Shoaib et al. (2000) PC 8 TI 62.70 21.42 3.30 5.23 2.40 2.35 2.41 0.45 2.71 N.R. 1.22 N.R.

Dyer et al. (1999) PC 9 TI 64.90 21.10 5.00 2.70 1.60 3.30 0.30 0.60 0.69 N.R. N.R. N.R.

Batis et al. (1996) PC 10 TI 65.50 20.54 4.74 3.74 1.52 2.61 0.10 0.48 0.42 N.R. N.R. N.R.

El-Sayed et al. (1991) PC 11 TI 62.66 20.40 5.19 3.26 2.62 2.37 2.48 0.32 2.69 0.30 1.17 366

Wang and Ramakrishnan

(1990) PC 12 TIII 63.05 20.98 6.13 2.61 1.39 2.50 N.R. N.R. N.R. 0.43 N.R. 540 Ramakrishnan and Balaguru (1987) PC 13 TII N.R. N.R. N.R. N.R. N.R. N.R. N.R. N.R. N.R. N.R. N.R. N.R.

Ramakrishnan and Balaguru (1987) PC 14 TIII N.R. N.R. N.R. N.R. N.R. N.R. N.R. N.R. N.R. N.R. N.R. N.R.

Ramakrishnan and Balaguru (1987)

Ramakrishnan (1986) PC 15 TI 70.27 19.93 1.83 3.03 1.93 2.58 N.R. 0.90 N.R. N.R. N.R. N.R.

Bhatty (1985a & 1986) PC 16 TI 64.60 21.40 5.10 3.50 2.10 1.70 0.23 0.46 0.53 0.70 1.10 326

Bhatty (1984, 1985b) PC 17 TI 63.85 20.16 4.75 2.51 1.46 3.93 0.10 0.47 0.41 0.78 2.13 441

Bhatty (1984, 1985b) PC 18 TI 63.33 21.10 4.90 2.57 2.08 2.78 0.15 0.83 0.70 0.93 1.05 398

Bhatty (1984, 1985b) PC 19 TI 63.02 24.06 4.20 2.68 2.29 2.51 0.15 0.39 0.41 0.60 0.71 313

Bhatty (1984, 1985b) PC 20 TI 62.66 21.12 4.42 2.05 3.95 2.78 0.16 0.93 0.77 0.88 1.74 438

Bhatty (1984) PC 21 TI 64.59 21.44 3.93 2.74 1.81 3.48 0.13 0.35 0.36 0.93 1.47 417

Ravindrarajah (1982) PC 22 TI 63.00 20.00 6.00 3.00 1.50 2.00 N.R. N.R. 1.00 0.00 2.00 N.R.

#

samples+ 16 16 16 16 16 16 14 15 15 9 12 8

Average+ 64.14 21.04 4.64 3.21 1.99 2.64 0.49 0.52 0.82 0.59 1.40 375

St. Dev. + 1.88 1.00 1.00 0.74 0.74 0.56 0.83 0.22 0.79 0.34 0.56 57

* PCs are numbered as they are referred to in subsequent discussion N.R. = Not Reported; Na2Oe = 0.658 x K2O + Na2O fCaO = free calcium oxide (free lime) and calcium hydroxide LOI = Loss on Ignition + only includes TI cements (PC 2, PC 12, PC 13, and PC 14 were excluded).

66

2.5.1.2 CKD-PC Mineralogical Composition

In the majority of studies, CKD mineralogical composition data is rarely reported. The

composition of a CKD consists of unreacted phases from the raw material, partially

calcined raw feed, condensed volatiles (alkalis, chlorides, and sulfates), and/or PC clinker

particles. Since CKDs are a by-product resulting from the partial decarbonation of

limestone (CaCO3), either free lime (free CaO) or calcite is expected to be the

predominant mineralogical component. Calcium carbonate is an important mineralogical

component of CKDs that can affect CKD-PC blend properties (Bhatty, 1985a). The

reported mineralogical composition data of CKD in the literature is shown in Table 2.13.

Although there are only eight data points for calcite content, the standard deviation

reflects its variability in CKDs.

Dyer et al. (1999) used Rietveld Refinement on X-ray diffraction traces over an angular

range of 3° to 80° 2θ using commercially available software program to estimate

proportions of the compounds present in CKDs 7 and 8; this is shown in Table 2.13. This

analysis, however, cannot be used as an estimate of the actual amount of the compounds

in the CKDs due to the lack of consideration for the amorphous content. Also, CKD 7

appears to be out of the ordinary since the free calcium oxide content is 0%.

As stated in the previous section, the CKD chemical components that can affect

properties of CKD-PC blends are alkalis, sulfates, chlorides, and free lime (Bhatty,

1985a). The chemical composition, however, is not the only important factor to consider

in assessing the potential impact of using a CKD-PC blend. The physical form of these

chemical components can also be significant. For example, alkalis are known to impact

cement properties, but can behave very differently if present in different forms. Readily

soluble alkali (alkali chlorides and alkali sulfates) can impact early hydration of PC much

more significantly than alkali found in crystal structures that are less soluble. Further,

alkali chlorides and alkali sulfates impact the hydration of PC differently.

67

Table 2.13 Mineralogical composition of CKD: from CKD-PC literature review

Mineralogical Phase CKD 2 CKD 7 CKD 8 CKD 13 CKD 14 CKD 15 CKD 16 CKD 17 Avg. St.Dev.

CaCO3 (calcite) + 8.9 52.8 50.94 22.65 60.4 44.58 64.68 43.56 20.45

CaO (free calcium oxide) + 0.0 1.4 + + + + +

Ca(OH)2 (portlandite) + 26.5 8.4

CaSO4 (anhydrite) + 9.8 6.1 + + + +

SiO2 (quartz) + 3.5 6.9 + + + + + Na2SO4

(thenardite) 7.9 0.0 Ca2Al(OH)6Cl2(H2O)2

(Friedel’s salt) 3.1 0.0 Na0.31K0.69Cl

(halite, potassium) + 0.0 2.9 K3Na(SO4)2 (aphthitalite) 0.0 10.2 +

K2Al4(Si6Al2O20)(OH)4 (Muscovite 2m1) 0.0 3.3

Ca2Si12Al4O32(H2O)12 (calcium harmotome) 0.0 0.9

KCl (sylvite) 20.4 7.0 +

K2Ca(SO4).H2O (syngenite) 19.9 0.0

K2SO4 (arcanite) 0.0 0.0 + + + + alpha C2S

(belite) + 0.0 0.0 CKD 2: El-Aleem (2005); CKD 7-8: Dyer (1999); CKD 13-15: Bhatty (1986), Bhatty (1985b), Bhatty (1985a), and Bhatty (1984); CKD 16: Bhatty (1985b) and Bhatty (1984); CKD 17: Bhatty (1984).

+: means it was identified as a component

68

2.5.1.3 CKD-PC Physical Composition

The majority of CKD-PC interaction studies do not report the physical characteristics of

the materials used. For the studies that did describe the physical properties of the

materials, the characterization methods consisted of Blaine fineness, particle size

distribution, percentage passing sieve, and density. Blaine fineness was the most

prominent method used to characterize the fineness of CKDs and PC, which is presented

in Table 2.11 and Table 2.12.

The range of the seven reported CKD Blaine fineness values is between 318 m2/kg and

718 m2/kg. The average Blaine fineness value of the 7 CKDs (510 m2/kg) is higher than

the average range of the PCs used in the same research studies (375 m2/kg). The standard

variation of the Blaine fineness for CKDs (122 m2/kg) is also higher in comparison to the

standard variation of Blaine fineness values for PC (57 m2/kg), as Blaine fineness in PC

is a process control parameter. The Blaine fineness values reported in the literature have

led some researchers to conclude that CKDs are finer than PC.

Wang et al. (2002) and Konsta-Gdoutos et al. (2001) were the only authors to have

provided particle size distribution analyses for the materials used in their CKD-PC

interaction study. CKD 5 and PC 7 particle size distributions are shown in Figure 2.14

(slag was also used in their research study and is included in the figure). Based upon the

particle size distribution curve, Wang et al. (2002) concluded that CKD 5 is coarser than

PC 7.

Ramakrishnan and Balaguru (1987) reported CKD 12 to be 98.56% passing a No. 200

sieve (70 µm), which is higher than each reported percentage passing a No. 200 sieve for

the three cements used in this research study (PC 13 = 95.20%, PC 14 = 97.90%, PC 15 =

95.50%). Based upon the 75 µm (No. 200 sieve), CKD 12 is finer than PC 14. The

density values are reported for CKD 4 (Udoeyo and Hyee, 2002) and CKD 18

69

(Ravindrarajah, 1982), which are 2.65 and 2.72 respectively. PC specific density is

generally accepted to be 3.15, although it generally varies between 3.1 and 3.2.

Figure 2.14 Particle size distribution of CKD 5 and PC 7 (Wang et al., 2002)

2.5.2 Workability

Maslehuddin et al. (2008a) studied the effect of replacing PC 3 with CKD 1 at 0%, 5%,

and 10% replacement by mass in pastes. The water required to maintain normal

consistency (ASTM C187) of PC alone was at a water to binder ratio (w/b) of 24.6%. The

w/b marginally increased to 24.9% at both 5% and 10% CKD replacement. Therefore, the

use of CKD 1 at up to 10% replacement of PC 3 did not significantly change the water

requirement.

El-Aleem et al. (2005) studied the workability effect of replacing PC 4 with CKD 2 at

0%, 2%, 4%, 6%, 8%, and 10% replacement by mass in pastes and mortars. The authors

observed that the addition of CKD increased the water required to maintain normal

consistency of pastes and constant flow of mortars (ASTM C1437), as shown in Figure

2.15 and Figure 2.16, respectively. As the amount of PC replacement with CKD

70

increased, the water demand also increased in both pastes and mortars. For the pastes, the

w/b increased almost linearly from 26.5% with no CKD replacement to 29.5% at 10%

CKD replacement of PC. For the mortars, the w/b also increased somewhat linearly from

0.485 with no CKD replacement of PC to 0.595 at 10% CKD replacement of PC.

El-Aleem et al. (2005) suggested that the increased water demand may be attributed to

the high amounts of alkalis, sulfates and volatile salts, and free lime in CKD 2 in

comparison to PC 4. El-Aleem et al. (2005) also mentioned that the slightly higher

surface area (Blaine fineness value) of CKD 2 could be a factor in the increased water

demand of pastes.

Figure 2.15 Paste water/binder ratio, initial set, and final set of CKD 2 as a partial

substitute of PC 4 at different levels of replacement (El-Aleem et al., 2005)

71

0.45

0.50

0.55

0 .60

0 2 4 6 8 10

CKD Replacement of PC, %

Wa

ter

/ b

ind

er

Figure 2.16 Mortar water/binder ratio of CKD 2 as a partial substitute of PC 4 at different

levels of replacement (El-Aleem et al., 2005)

Al-Harthy et al. (2003) determined the water demand of mortar mixes to maintain the

same workability using CKD 3 at a 0%, 10%, 20%, 25%, and 30% replacement level of

PC 5, as shown in Figure 2.17. As the level of CKD 3 replacement increased in the

mortar mixes, the water demand also increased. The w/b increased almost linearly from

0.644 with no CKD to 0.677 at 10% CKD replacement of PC and 0.759 at 25%

replacement. At 30% replacement, however, the water requirement decreased to w/b of

0.731. Al-Harthy et al. (2003) stated that the increased cohesiveness of the mortar mixes

is caused by the very fine particles of CKD. It is not clear whether the sudden w/b

decrease as the CKD increased from 25% to 30% replacement is caused by a chemical or

physical effect. Al-Harthy et al. (2003) also reported the workability effect using 0%, 5%,

10%, 15%, 20%, 25%, and 30% CKD 3 replacement by total mass of PC 5 in concrete

mixtures. Three w/b ratios of 0.50, 0.60, and 0.70 were used for each concrete mixture.

For each level of w/b ratio, the measured slump was the same or it decreased as the

amount of CKD replacement level increased. As the w/b ratio increased, the impact of

CKD 3 replacement of PC 5 on slump loss became more significant.

72

0 .60

0.65

0.70

0.75

0 .80

0 10 20 25 30

CKD Replacement of PC, %

Wa

ter

/ b

ind

er

Figure 2.17 Mortar water/binder ratio of CKD 3 as a partial substitute of PC 5 at different

levels of replacement (Al-Harthy et al., 2003)

Udoeyo and Hyee (2002) studied the workability effect of CKD 4 substitution at 0%,

20%, 40%, 60%, and 80% of PC 6 in concrete mixes. Each concrete mix was batched

according to the mix ratio of 1:3:4:0.65 (binder: sand: coarse aggregate: water). The

results show that as the CKD replacement level increases, the measured slump decreases.

Udoeyo and Hyee (2002) did not suggest mechanisms for the loss of slump in the CKD-

PC concrete mixes.

Wang et al. (2002) conducted viscosity tests on pastes with CKD 5 at partial replacement

levels of PC 7 at 0%, 15%, 25%, and 50% with a w/b ratio of 0.50. They further reported

that the viscosity of the pastes, measured using a rheometer with coaxial cylinders,

increased as the amount of CKD used to replace the cement increased. Wang et al.

(2002) suggested three factors that could contribute to increased viscosity. First, CKD 5

is coarser than PC 7, based upon the particle size distribution comparison shown in

Figure 2.10 and is, therefore, increasingly viscous. The authors state that coarse particles

73

can behave independently of colloidal particles and act as amplifiers that increase the

viscosity of a concentrated suspension system, such as fresh cement paste. The authors

cited research conducted by Sengun and Probstein (1997) that used bimodal suspensions

containing both colloidal and noncolloidal size particles, where a particle size ratio

typically larger than 10 is treated as bimodal. It should be noted, however, that the fine

and coarse fraction of a CKD generally has only a small fraction of the particle size ratio

greater than 10. Second, there is an increase in rapid ion dissolution during the early

stages of hydration due to the presence of CKD, which may result in high viscosity.

Third, the size irregularity of CKD particles may increase friction between the cement

and CKD particles when compared to paste with cement particles only.

Wang and Ramakrishnan (1990) investigated the workability of pastes and concrete made

with a binary blend consisting of 5% CKD (CKD 12) and 95% TIII cement (PC 12). The

normal consistency w/b ratio for the plain cement paste was 27.0% and the paste with

CKD 12 had a w/b ratio of 28.0%. Although the water content required for normal

consistency was 1% higher, the authors did not believe this necessarily meant that the

CKD-PC blend needed a higher water content to produce the same concrete slump as a

plain cement. Wang and Ramakrishnan (1990) stated that the Vicat paste test measures

viscosity whereas the concrete slump test indicates the lubricating ability of the paste.

The concrete mixes were tested at three w/b ratios: 0.45, 0.52, and 0.55. Wang and

Ramakrishnan (1990) reported there was no significant difference in the slump between

the plain and CKD blended concretes.

Ramakrishnan (1986) investigated the workability of pastes and concrete made with a

binary blend consisting of 5% CKD (CKD 12) and 95% TI cement (PC 15). The w/b

ratio for the plain cement paste was 0.245 and the paste with CKD 12 had a w/b ratio of

0.255. The CKD-PC blend had 1% higher normal consistency than the plain cement. The

concrete mixes were tested at a cement content of 386 kg/m3 and w/b ratio of 0.45. Six

74

sets of each concrete mix were batched. Ramakrishnan (1990) reported there was no

significant difference in the slump between the plain and CKD blended concretes.

Bhatty (1985a) used a TI cement (PC 16) with three different CKDs (CKD 13, CKD 14,

and CKD 15) to investigate their effect on paste workability. CKD-PC blends were

prepared by replacing 0%, 10%, and 20% of cement at a w/b ratio of 0.45. Workability

was determined by the size of a mini-slump pat area and was consistently reduced for

blends with CKD compared to the control pastes. Although the workability of all CKD-

PC blends decreased as the amount of CKD increased from 10% to 20%, the magnitude

varied significantly.

Bhatty (1984) also conducted mini-slump pat area studies on pastes using five companion

cements and CKD obtained from five different cement plants. The five companion

cement kiln dust blends were: PC 17 and CKD 13, PC 18 and CKD 14, PC 19 and CKD

15, PC 20 and CKD 16, and PC 21 and CKD 17. For each CKD-PC blend, the CKD

replacement of the cement was 0%, 10%, 15%, and 20% by mass at a w/b ratio of 0.50.

As the percentage of CKD replacement increased, the blends containing CKD 13, CKD

14, CKD 16, and CKD 17 generally decreased workability. The opposite trend was

observed for blends with CKD 15. Bhatty (1984) stated that as the amount of high

chloride from the CKD increased in the CKD blends, workability also increased.

Ravindrarajah (1982) used pastes and concrete to study the workability effect of CKD-PC

interaction. For pastes, CKD 18 was used as a partial cement replacement of PC 22 by

mass at 0%, 25%, 50%, 75%, and 100%. Water was added to each paste mix to maintain

a standard consistency. The author reported that as the percentage of CKD increased in

the cement paste, the amount of water had to increase in order to attain a normal

consistency. For concrete, CKD 18 was used as a partial cement replacement of PC 22 by

mass at 0%, 15%, 25%, 35%, and 45%. Water was added to each concrete mix to

maintain the same slump for all concrete mixes. Similar to pastes, Ravindrarajah (1982)

75

determined that as the CKD percentage increased in the concrete mix, the water demand

to maintain the same slump also increased. The author attributed the increased water

demand in pastes and concrete to the higher surface area (Blaine fineness) of the kiln dust

compared to cement and the increased solid volume of the mix (since the density of CKD

is lower than that of cement).

A summary of the studies conducted on the workability effects of CKD-PC blends

compared to each of the respective reference plain cements is shown in Table 2.14. The

majority of researchers found that the workability was reduced as the amount of CKD

increased, and that the trend was somewhat linear until a plateau was reached. The

suggested reasons for a reduction in workability when CKD is used as a partial substitute

for PC vary considerably: CKD alkali content, chloride content, sulfate and volatile salts

content, lime content, a high fineness of CKD, rapid ion dissolution, high coarseness of

CKD, particle size, and lower density of CKD. It is interesting to note that both higher

fineness (based upon Blaine fineness) and higher coarseness (based upon particle size

distribution) of CKD compared to cement were suggested to have the same impact of

reducing workability of pastes. The researcher with the only CKD-PC blend that

increased workability stated that as the amount of high chloride from the CKD increased

in the CKD blends, workability also increased. Chlorides, however, are not widely

known to impact workability (refer to 2.4.7).

76

Table 2.14 Workability: from CKD-PC literature review

Author(s)

Blend Type w/b % CKD Replacement

General Effect on

Workability

Author Suggested Mechanism(s)

Maslehuddin et al. (2008a)

CKD 1/PC 3 P V 0,5,10 N.C.

El-Aleem et al. (2005)

CKD 2/PC 4 P M

V V

0,2,4,6,8,10 0,2,4,6,8,10

↓

↓

(1) Higher amounts of alkalis, sulfates and volatile salts, and lime in CKD.

(2) Higher Blaine fineness in CKD.

Al-Harthy et al. (2003)

CKD 3/PC 5 M C

V K

0,10,20,25,30 0,10,20,25,30

↓

↓

(3) Increased cohesiveness caused by very fine CKD particles in pastes.

(4) Impact of CKD replacement in concrete was more dramatic at higher w/b ratios.

Udoeyo and Hyee (2002)

CKD 4/PC 6 C 0.65 0,20,40,60,80 ↓

Wang et al. (2002)

CKD 5/PC 7 P 0.50 0,15,25,50 ↓ (5) CKD coarseness increases viscosity.

(6) Rapid ion dissolution due to presence of CKD.

(7) CKD particle size irregularity

Wang and Ramakrishnan (1990)

CKD 12/PC 12 P C

V 0.45

0,5 0,5

↓ N.C.

Ramakrishnan (1986)

CKD 12/PC 15 P C

V 0.45

0,5 0,5

↓ N.C.

Bhatty (1985a)

CKD 13/PC 16 CKD 14/PC 16 CKD 15/PC 16

P P P

0.45 0.45 0.45

0,10,20 0,10,20 0,10,20

↓ ↓ ↓

Bhatty (1984)

CKD 13/PC 17 CKD 14/PC 18 CKD 15/PC 19 CKD 16/PC 20 CKD 17/PC 21

P P P P P

0.50 0.50 0.50 0.50 0.50

0,10,15,20 0,10,15,20 0,10,15,20 0,10,15,20 0,10,15,20

↓ ↓ ↑ ↓ ↓

(8) As the amount of high chloride from the CKD increased in the CKD blends, workability also increased.


CKD 18/PC 22 P C

V V

0,25,50,75,100 0,15,25,35,45

↓ ↓

(9) Higher fineness of the CKD in comparison to the PC

(10) Increased solid volume (since the density of the CKD is lower than that of the cement).

P = Paste; M = Mortar; C = Concrete. V = varied the w/b ratio to maintain consistent workability K = constant w/b ratio, but more than one w/b ratio was tested. N.C. = No Change

77

2.5.3 Setting Time

Maslehuddin et al. (2008a) studied the setting time effect of replacing PC 3 with CKD 1

at 0%, 5%, and 10% replacement by mass in pastes, with water added to maintain a

constant normal consistency according to ASTM C187 and ASTM C191. The plain

cement paste had an initial setting time of 175 minutes and a final setting time of 256

minutes. The initial and final setting times of the paste with 5% CKD replacement were

10 minutes (6%) and 6 minutes (2%) faster than the control plain cement, respectively.

The initial and final setting times of the paste with 10% CKD replacement were 20

minutes (11%) and 18 minutes (7%) faster than the control plain cement, respectively.

The authors attributed the decrease in both initial and final setting times to the high

amounts of lime and alkalis in the CKD, which accelerate the hydration process leading

to faster setting times.

El-Aleem et al. (2005) studied the set time effect of replacing PC 4 with CKD 2 at 0%,

2%, 4%, 6%, 8%, and 10% replacement by mass in pastes, with water added to maintain

a constant normal consistency. El-Aleem et al. (2005) reported that as the CKD

replacement increases, the water demand increases and the setting time decreases. This is

contrary to what many expect since it is well known that an increase in w/b results in

longer settings times for a given paste. It is important to note that the established

influence of w/b refers to its effect on a single blend and not on blends with different

chemical/mineralogical and physical properties. As shown in Figure 2.15, the decrease of

both initial and final setting times is almost linear as a function of CKD replacement. The

initial set time decreased from approximately 135 minutes with no CKD to approximately

65 minutes with 10% CKD replacement of PC. The final set time decreased from

approximately 230 minutes with no CKD to approximately 110 minutes with 10% CKD

replacement of PC. Similar to Maslehuddin et al. (2008a), El-Aleem et al. (2005)

suggested that this was due to the high amounts of lime and alkalis in CKD.

78

Udoeyo and Hyee (2002) studied the setting time effect of replacing PC 6 with CKD 4 at

20%, 40%, 60%, and 80% replacement by mass in concrete at a w/b ratio of 0.65.

Udoeyo and Hyee (2002) reported that at a 20% CKD 4 replacement level of PC 6, the

initial setting time increased slightly from 0.72 h to 0.78 h, and the final set time

remained unchanged at 1.62 h. As the CKD 4 content increased beyond 20%

replacement, the set time increased significantly. At a very high replacement level of

80%, the initial set time was 1.33 h and final set time was 2.5 h. Udoeyo and Hyee (2002)

stated that the values of the initial and final setting times were within the relevant BS and

ASTM standards, but did not suggest possible mechanisms for the increased setting

times.

Wang and Ramakrishnan (1990) used CKD 12 at 5% cement replacement of a TIII

cement (PC 12) to determine the impact on paste and concrete setting time. The normal

consistency w/b ratio for the plain cement paste was 27.0% and the paste with CKD 11

had a w/b ratio of 28.0%. The plain cement paste had an initial setting time of 122

minutes and a final setting time of 155 minutes. The CKD-PC blend initial and final

setting times were 45 minutes (38%) and 53 minutes (34%) longer than the control plain

cement, respectively. Wang and Ramakrishnan (1990) attributed the longer setting times

of the CKD paste to the higher water content required to maintain normal consistency.

The concrete mixes were tested at three w/b ratios: 0.45, 0.52, and 0.55. The effects of

CKD on the initial and final setting times of concrete were determined by concrete

penetration resistance (ASTM C403). Both the initial and final set of the CKD-PC

concrete occurred 30 minutes later than for plain concrete (the w/b ratio for the concrete

mixes used to assess setting times was not specified). Wang and Ramakrishnan (1990)

did not suggest possible mechanisms for the increase in concrete setting times.

Ramakrishnan (1986) used CKD 12 at 5% cement replacement of a Type I cement (PC

15) to determine the impact on paste (ASTM C191) and concrete setting time (ASTM

C403). The w/b ratio for the plain cement paste was 24.5% and the paste with CKD 12

79

had a w/b ratio of 25.5%. Ramakrishnan (1986) stated that the initial and final setting

times of the CKD-PC blend were longer than that of the plain cement. The author

reported the differences to be 22 minutes and 40 minutes, respectively, for initial and

final setting times. The concrete mixes were tested at a cement content of 386 kg/m3 and

w/b ratio of 0.45. Six sets of each concrete mix were batched. Ramakrishnan (1986)

reported the initial and final setting time for one of the six concrete mixes for each of the

CKD blend and plain cement. The initial and final setting times for the plain cement

concrete mix was 5 hours and 42 minutes and 7 hours and 20 minutes, respectively. The

initial and final setting times for the concrete mix with CKD 12 were 6 hours and 4

minutes and 7 hours and 48 minutes, respectively. Ramakrishnan (1986) concluded that

the setting time of the CKD pastes was slightly longer than the plain cement paste, but

the setting time of the CKD concrete mix and plain concrete mix were almost the same

(within 5%). It is important to note, however, that the concrete initial and final setting

times of the CKD concrete mixes were 22 minutes and 28 minutes, respectively, longer

than the plain concrete mix.

Bhatty (1985a) used a TI cement (PC 16) with three different CKDs (CKD 13, CKD 14,

and CKD 15) to investigate their effect on paste set time. Cement and CKD blends were

prepared by replacing 0%, 10%, and 20% of cement at a w/b ratio of 0.45. Bhatty (1985a)

stated that time of initial set was always shorter compared to cement for any blends

containing 10% CKD. Longer time of initial set was obtained for blends made with 20%

CKD 13 and 20% CKD 15, as compared to blends made with 10% of CKD 13 and 10%

of CKD 15 or to cement alone. The blend made with 20% of CKD 14 had a considerably

shorter time of initial set when compared to all other CKD blends and cement alone.

CKD 14 is characterized by high sulfate (11.10%), high free lime (21.72%), and low

chloride (0.26%) contents.

Bhatty (1984) also conducted setting time tests on pastes using five companion cements

and dusts obtained from five different cement plants. The five companion cement kiln

80

dust blends are: PC 17 and CKD 13, PC 18 and CKD 14, PC 19 and CKD 15, PC 20 and

CKD 16, and PC 21 and CKD 17. For each cement kiln dust blend, the CKD replacement

of the cement was 0%, 10%, 15%, and 20% at a w/b ratio of 0.50. As the CKD

replacement level increased, the setting time for blends with CKD 13, CKD 14, CKD 16,

and CKD 17 decreased. Blends with CKD 15 had the opposite effect and increased

setting time. Bhatty (1984) concluded that the time of set generally decreased with

increased dust addition levels, although no effects of CKD chemistry were specified.

Ravindrarajah (1982) used cement pastes to assess the set time of partial and complete

replacement of cement with CKD 18 and PC 22. Cement was partially replaced by mass

at 0%, 25%, 50%, 75%, and 100%. The pastes were mixed with necessary water content

to produce a consistent workability. As the percentage of cement replacement increased,

the final setting time increased. The data shows that all samples had set within 10 hours,

which was the specified limit in the British Standard. The initial setting time also

lengthened, but the rate of increase slowed after 50% of cement had been replaced by

CKD. Ravindrarajah (1982) stated that the increased set times are opposite to what is

expected with CKDs, since a higher alkali concentration promotes shortened setting

times. The author suggested the effect of increased set time may be attributed to (i) the

physical presence of inactive particles and (ii) the kiln dust that acted as a barrier between

the cement particles and water. The nature of the suggested barrier was not specified by

the author.

A summary of the studies conducted on the setting time effects of CKD-PC blends

compared to each of the respective reference plain cement is shown in Table 2.15. The

effect of CKDs on setting times is decidedly mixed. The same CKD at different

replacement levels of a PC can have different effects on setting time. The setting time

impact of CKD is likely a function of the total composition of the CKD-PC blend.

81

Table 2.15 Setting time: from CKD-PC literature review

Author(s)


General Effect on Setting

Time



CKD 1/PC 3 P V 0,5,10 ↓

(1) High amounts of lime and alkalis in CKD accelerate hydration and lead to fast setting.


CKD 2/PC 4 P

V

0,2,4,6,8,10

↓

(2) High amounts of lime and alkalis in CKD accelerate hydration and lead to fast setting.


CKD 4/PC 6 C 0.65 0,20,40,60,80 ↑


CKD 12/PC 12 P C

V N.R.

0,5 0,5

↑ ↑

(3) Higher set times in paste attributed to higher water demand due to the CKD.

Ramakrishnan (1986)

CKD 12/PC 15 P C

V 0.45

0,5 0,5

↑ N.C.

Bhatty (1985a)


P P P

0.45 0.45 0.45

0,10,20 0,10,20 0,10,20

10% ↓; 20% ↑ 10% ↓; 20% ↓ 10% ↓; 20% ↑

Bhatty (1984)


P P P P P

0.50 0.50 0.50 0.50 0.50

0,10,15,20 0,10,15,20 0,10,15,20 0,10,15,20 0,10,15,20

↓ ↓ ↑ ↓ ↓


CKD 18/PC 22 P C

V V 0,25,50,75,100

0,15,25,35,45

↑ ↑

(1) Physical presence of inactive particles in the kiln dust.

(2) The dust may act as a barrier between the cement particles and water.

P = Paste; M = Mortar; C = Concrete. V = varied w/b ratio to maintain consistent workability K = constant w/b ratio, but more than one w/b ratio was tested. N.C. = No Change

82

2.5.4 Hydration Kinetics

El-Aleem et al. (2005) studied the hydration behavior effect of replacing PC 4 with CKD

2 at 0%, 2%, 4%, 6%, 8%, and 10% replacement by mass in pastes with water added to

maintain a constant normal consistency. El-Aleem et al. (2005) assessed the hydration

behaviour of each mix by determining the free lime as well as evaporable water and

chemically combined water contents at 3, 7, 28, and 90 days, as shown in Figure 2.18.

The free lime was determined using the alcohol ammonium acetate method, which does

not distinguish between calcium oxide and calcium hydroxide. The evaporable water

content of the hardened paste was determined by subtracting the total water content (loss

on ignition at 1000°C of the saturated sample) from the combined water content (loss on

ignition at 1000°C for 2 hours). The authors reported that the quantity of free lime

increased with curing time due to the continuous hydration of the main cement phases

and leaching from CKD 2.

El-Aleem et al. (2005) also noted that at any given time, the quantity of free lime

increased with CKD 2 content in the blend. Continuous hydration of the cement phases

led to a decrease in evaporable water. It was reported that the evaporable water content in

pastes increased with the CKD 2 content due to the increase in mixing water and low or

no hydraulic properties of CKD 2, in comparison to the high hydraulic cement properties

of PC 4. Generally, the hydration and accumulation of hydration products mainly as

calcium silicate and sulfoaluminate hydrates cause the chemically combined water

content to decrease. The cement pastes with CKD 2 and PC 4 exhibited lower values of

combined water content than the control PC 4 paste. This indicated to the authors that the

C-S-H formed in the blends with CKD 2 and PC 4 blend is lower than that in PC 4 alone.

83

(a)

(b)

(c)

Figure 2.18 Hydration of pastes showing (a) evaporable water content (%), (b) free lime

content (%) (calcium oxide and calcium hydroxide), and (c) chemically combined water

content, as a function of time at different percentage levels of PC 4 replacement with

CKD 2 (El-Aleem et al., 2005)

I.1 Control I.2 2% CKD I.3 4% CKD I.4 6% CKD I.5 8% CKD

I.6 10% CKD

84

Wang et al. (2002) conducted hydration tests on pastes with CKD 5 at partial replacement

levels of PC 7 at 0%, 15%, 25%, and 50% with a w/b ratio of 0.50 using adiabatic

calorimetric tests. Wang et al. (2002) reported that during initial hydrolysis the pastes

with partial replacement of PC 7 with CKD 5 had a much higher heat of evolution than

the pastes with PC 7 alone. The induction period began and ended much later than for the

pastes with cement alone. The authors suggested that both of these characteristics may be

due to the high alkali content of the CKD, which may accelerate ion dissolution of the

silicates in the binder system resulting in a high initial heat evolution and an extended ion

dissolution period. The cement paste with 15% CKD and 85% cement produced a higher

heat peak value for rate of heat evolution than the paste with cement alone. The authors

stated this higher value generally reflects the hydration of C3S and C2S in PC and implied

that the binder system may have an optimum alkali to silicate ratio. They stated that the

alkalis, mainly from the CKD, may facilitate dissolution of the silicates and accelerate the

formation of calcium silicate hydrates (C-S-H). The paste with 25% CKD and 75% PC,

however, had a lower heat peak value for rate of heat evolution than the paste with 15%

CKD and 85% cement. Wang et al. (2002) reported that as the percentage of cement

replaced with CKD increased, the heat evolution decreased when the CKD content was

greater than a certain proportion. Additionally, excessive amounts of alkalis in the paste

may have depressed dissolution and retarded hydration of the silicates. The peak

appearance of the 25% CKD paste was delayed when compared to the 15% CKD paste

and plain cement paste. Wang et al. (2002) concluded that for a specified CKD content,

the peak rate of heat evolution increased as the alkali:silica ratio in the paste also

increased. The high peak rate of heat evolution generally indicates early strength

development.

Dyer et al. (1999) studied the hydration chemistry of cement pastes using two CKDs

(CKD 7 and CKD 8) and one cement (PC 9). Dyer et al. (1999) used isothermal

conduction calorimetry to assess the maximum rate heat evolution and the time at which

this peak occurs at 0%, 20%, 35%, 50%, and 75% CKD replacement of PC. The w/b ratio

85

was 0.50 for each paste. The results from the magnitude of the maximum heat rate

evolution indicated that both types of CKD accelerated the hydration of cement. The

results for the time at which the peak occurred, however, indicated that the CKDs had the

effect of slowing hydration. Dyer et al. (1999) suggested two possible reasons for the

conflicting results. First, the combination of potassium chloride (which accelerates

hydration) and sulfate compounds (which generally accelerates the hydration of calcium

silicate cement phases while retarding the hydration of calcium aluminate phases) in each

CKD could produce this effect. Second, a dense membrane of initial hydration products

could be forming on the cement grains as a result of the large amounts of ions released

into solution by each CKD. CKDs commonly consist of water soluble compounds – such

as alkali chlorides, alkali sulfates, and lime – that result in highly alkaline solutions when

mixed with water (Dyer et al., 1999). The high pH levels produced by each CKD

dissolving into solution are also likely to promote the formation of hydration products

and lead to higher heat evolved values. Dyer et al. (1999) also arrested hydration of the

cement pastes at 2, 7, and 28 days. As discussed in the report, the hydration of pastes

with cement alone typically involves the reduction of sulfate ions to the point at which

further formation of AFt becomes impossible and AFm hydrates begin to form. Dyer et

al. (1999) concluded that the increased quantities of sulfate introduced as part of each

CKD inhibited the conversion of AFt to AFm phases. This led to increased AFt for these

blends. Further, there were two AFm phases identified in the CKD-PC blends at later

ages: calcium monosulphoaluminate hydrate (typical) and calcium monochloroaluminate

hydrate (Friedel’s salt which is atypical). Dyer et al. (1999) noted that Friedel’s salt only

forms when the free sulfate ions have already been largely consumed.

A summary of the limited number of studies conducted on the hydration effects of CKD-

PC blends compared to each reference plain cement is shown in Table 2.16. The effects

of CKD-PC blends were reported to be higher free lime (calcium oxide and calcium

hydroxide) in the paste, less C-S-H formation, higher heat evolution during initial

hydrolysis, delayed beginning and end of induction period, higher maximum heat value at

86

15% CKD replacement and lower maximum heat value at 25% CKD replacement,

delayed maximum heat value, higher AFt content, and the presence of Friedel’s salt at

less than 28 days. The suggested mechanisms of a CKD-PC blend upon hydration are:

higher alkali concentration in solution causing acceleration or retardation of silicate

dissolution depending upon the alkali/silicate ratio, higher chloride, and higher sulfate

contents.

Table 2.16 Hydration: from CKD-PC literature review Author(s)

Blend General Effect on Paste Hydration



CKD 2/PC 4 (1) Higher free lime content. (2) Less C-S-H formation

(1) Higher CKD free lime content. (2) Lower chemically combined H2O (3) Higher evaporable H2O

Wang et al. (2002) CKD 5/PC 7 (3) Higher heat evolution during initial hydrolysis.

(4) Induction period began and ended later.

(5) Higher maximum heat value at 15% CKD replacement of PC, but lower maximum heat value at 25% CKD replacement level.

(4) High alkali dissolution during initial hydrolysis cause effects (4) and (5).

(5) Optimum alkali:silica ratio at 15% CKD replacement of PC.

(6) Excessive amounts of CKD depress dissolution and retard hydration of silicates at 25% CKD replacement of PC.

Dyer et al. (1999) CKD 7/PC 9 CKD 8/PC 9

(6) Higher maximum heat value. (7) Time of maximum heat value

was delayed. (8) Higher ettringite (AFt)

content. (9) Friedel’s salt present at <

28days.

(7) Combined effect of potassium chloride and sulfate compounds could cause effects (7) and (8).

(8) Rapid ion dissolution form a dense membrane of initial hydration productcs. Higher pH, however, is less likely to promote hydration products and higher heat values.

(9) High CKD sulfate content cause effect (8). (10) High chloride content cause effect (9).

87

2.5.5 Compressive Strength

Maslehuddin et al. (2008b) studied the compressive strength effect of replacing PC 1 (TI)

and PC 2 (TV) with CKD 1 at 0%, 5%, 10%, and 15% replacement by mass in concrete.

The compressive strength development after 3, 7, 14, 28, 56, and 90 days of curing were

tested, according to ASTM C39. The compressive strength development at the different

percentage levels of CKD 1 replacement of PC 1 and PC 2 is shown in Figure 2.19. For

PC 1, all of the concrete mixes with CKD 1 at 3 and 7 days had lower compressive

strength (>5%) than PC 1 alone. At all other ages, the compressive strength of 0% and

5% CKD concrete mixes with PC 1 was similar (±5%). The PC 1 concrete mixes

incorporating 10% and 15% CKD 1 had lower compressive strength (>5%) in

comparison to PC 1 alone at ages tested after 7 days. For PC 2, the compressive strength

of 0% and 5% CKD concrete mixes with PC 2 was similar (±5%) at all ages tested except

56 days (>10%). However, there was generally a decrease in compressive strength (>5%)

in the PC 2 concrete mixes with 10% and 15% CKD 1 at all ages, in comparison to PC 2

alone. The authors concluded that up to 5% CKD could be used without apprehension of

the reduction in compressive strength, despite the low compressive strength with PC 1 at

3 and 7 days and low compressive strength with PC 2 at 56 days.

88

(a)

(b)

Figure 2.19 Concrete compressive strength of CKD 1 at different replacement levels of

(a) PC 1 and (b) PC 2 (Maslehuddin et al., 2008b)

89

Maslehuddin et al. (2008a) studied the compressive strength effect of replacing PC 3 with

CKD 1 at 0%, 5%, and 10% replacement by mass in mortars. The mortar mixes had a w/b

ratio of 0.485 and were tested at 1, 3, 7, and 28 days. The compressive strength of all

CKD-PC blends was higher than PC alone at all ages, as shown in Table 2.17. At 1 day,

the blends with CKD at 5% and 10% replacement had 28% and 34% higher strength than

PC alone, respectively. At 3 days, the blends with CKD at 5% and 10% replacement had

44% and 51% higher strength than PC alone, respectively. At 7 days, the blends with

CKD at 5% and 10% replacement had 20% and 21% higher strength than PC alone,

respectively. Finally, at 28 days, the blends with CKD at 5% and 10% replacement had

5% and 11% higher strength than PC alone, respectively. At all ages, the compressive

strength increased as the quantity of CKD in the mortar mixes increased.

Table 2.17 Mortar compressive strength of CKD 1 at 0%, 5%, and 10% replacement of

PC 3 as a function of time (Maslehuddin et al., 2008a)

Average Compressive Strength (MPa)

1 day 3 day 7 day 28 day

100% PC 3 6.31 15.04 22.93 33.17

95% PC 3, 5% CKD 1 8.09 21.60 27.60 34.79

90% PC 3, 10% CKD 1 8.43 22.71 27.69 36.89

El-Aleem et al. (2005) studied the compressive strength effect of replacing PC 4 with

CKD 2 at 0%, 2%, 4%, 6%, 8%, and 10% replacement in mortars according to ASTM

C109. The w/b ratio was increased to maintain a constant flow. The mortar compressive

strength tests were conducted at 3, 7, 28, and 90 days, as shown in Figure 2.20. El-Aleem

et al. (2005) reported that the compressive strength for mortar cubes decreased slightly at

all ages with CKD content of up to 6%. Above this percentage, the compressive strength

decreased sharply. The reduction of compressive strength is suggested to be caused by:

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(i) the reduction in the cement content, (ii) an increase in the w/b ratio as the percentage

of CKD in the blend increased, (iii) an increase in free lime content in cement dust; the

higher amount of Ca(OH)2 weakened the hardened matrix, (iv) the formation of chloro-

and sulfoaluminate phases leads to the softening and expansion of the hydration products,

and (v) the porosity also increases, due to the high chloride (7.5%) and sulfate (5.10%)

content of CKD 1 (Note: the formation of these products enhances the crystallization of

hydration products leading to an opening of the pore system). El-Aleem et al. (2005)

concluded that the substitution of PC with CKD up to 6% has no significant effect on the

compressive strength of hardened mortar.

Figure 2.20 Mortar compressive strength as a function of time at different percentage

levels of CKD 2 replacement of PC 4 (El-Aleem et al., 2005)

I.1 Control I.2 2% CKD I.3 4% CKD I.4 6% CKD I.5 8% CKD

I.6 10% CKD

91

Al-Harthy et al. (2003) investigated the compressive strength effect of using CKD 3 as a

partial replacement of PC 5 using mortars. The different mortar levels of CKD

replacement of PC by mass were 0%, 10%, 20%, 25%, and 30%. The w/b ratio of each

mortar mix varied to maintain constant flow. The mortar mixes were tested at 28 days

and showed the CKD blended strengths to be lower than the control (31 MPa). Al-Harthy

et al. (2003) attributed the lower strengths to the higher w/b ratios of the CKD blended

mortars. The 10% CKD blend had a compressive strength of 27 MPa and the 20% CKD

blend had a compressive strength of 23 MPa. It is interesting to note that the 25% CKD

blend (24 MPa) and 30% CKD blend (24 MPa) had comparable strengths to the 20%

CKD blend.

Al-Harthy et al. (2003) also used seven different concrete mixtures that were prepared

using 0 (control), 5, 10, 15, 20, 25, and 30% CKD 3 replacement by total mass of PC 5.

For each mixture, three water-binder ratios of 0.70, 0.60, and 0.50 by mass were used and

the ages tested were 3, 7, and 28 days, as shown in Figure 2.21. A major observation by

the authors was that there is generally a decrease in compressive strength with an increase

in CKD replacement for cement. The authors also observed that there is more decrease in

compressive strengths in mixes with higher w/b ratios (0.70) than in those mixes with

low w/b ratios (0.50). At 5% and 10% CKD 3 substitution for PC 5, the reductions in the

28 day compressive strength were 1.8% and 4.5%, respectively (w/b of 0.50). At higher

w/b ratio (0.60) the 28 day compressive strength reductions were more significant (12.4%

and 18% decreases in strength for 5% and 10% CKD 3 replacement of PC 5). Al-Harthy

et al. (2003) stated that CKD is not highly cementitious and the replacement of cement by

CKD will lead to less cement content and, therefore, less strength. However, small

amounts of 5% and 10% CKD substitution do not seem to have an appreciable adverse

effect on strength, especially at low w/b ratios.

92

(a)

(b)

(b)

(c)

Figure 2.21 Concrete compressive strengths, w/b (a) 0.70, (b) 0.60, and (c) 0.50, at

different percentage levels of CKD 3 replacement of PC 5 (Al-Harthy et al., 2003)

93

Udoeyo and Hyee (2002) studied the compressive strength effect of replacing PC 6 with

CKD 4 at 20%, 40%, 60%, 80%, and 100% replacement in concrete at a w/b ratio of

0.65. The tests were conducted at 1, 3, 7, and 28 days. Udoeyo and Hyee (2002) reported

that the strength decreased with an increase in CKD content at these very high

replacement levels. For example, the 28-day reduction in compressive strength compared

to the plain concrete was 7.5%, 33.2%, 71.8%, and 85.3%, respectively, for concrete with

20%, 40%, 60%, and 80% replacement levels of PC 6 with CKD 4. The strength results

suggest that CKD 4 is poorly hydraulic.

Wang et al. (2002) studied the effect of CKD 5 at partial replacement levels of PC 7 at

0%, 15%, and 25% on 28-day compressive strength with mortars at a w/b ratio of 0.50.

Wang et al. (2002) found that the compressive strength of blends with CKD and cement

increased with the CKD replacement of cement up to 15% (47.8 MPa) in comparison to

cement alone (46.3 MPa). The specimen with 25% CKD (39.4 MPa) had a much lower

compressive strength than the plain cement specimen. Wang et al. (2002) stated that it is

commonly accepted that the low hydraulic property of CKD causes the compressive

strength to decrease as the amount of CKD replacement increases. Wang et al. (2002)

also suggested that the increased strength in the specimen with 15% CKD may be

attributed to an appropriate alkalinity that increases the dissolution of silicate species and

formation of C-S-H. The authors also noted that 15% CKD replacement of PC

significantly reduces the volume fraction of pores larger than 3 µm, which may result in

improved strength.

Shoaib et al. (2000) conducted compression strength tests on concrete using CKD 6 as a

partial replacement of PC 8 at 0%, 10%, 20%, 30%, and 40% and a w/b ratio of 0.5. The

tests were conducted at one, three, and six months. The authors reported that the

compressive strength decreased with increasing amounts of CKD. Shoaib et al. (2000)

concluded that the critical value of CKD replacement of cement for compressive strength

requirements is 10%. They attributed the compressive strength loss to the reduction in

94

cement clinker, which is mainly responsible for strength development. They also

concluded that the higher concentration of chlorides present in CKD led to a reduction of

strength. It was reported that the chlorides caused the hydration products to crystallize,

which resulted in an increase in the total porosity of the hardened sample, thus reducing

the compressive strength. The authors further stated that the chloride ions take part in

chemical reactions (similar to those involving sulfate ions) and yield chloro-aluminate

hydrate 3CaO.Al2O3.CaCl2.12H2O, which can cause softening. Shoaib et al. (2000)

reported that due to the presence of alkalis, the microstructure of C-S-H phases became

heterogeneous and lowered the ultimate compressive strength.

Batis et al. (1996) used PC 10 and two CKDs (CKD 9 and CKD 10) for testing 90-day

compressive strength concrete containing CKD. Each CKD was added as a 6% partial

cement replacement, and the w/b ratio was varied at 0.65, and 0.75. At w/b ratio of 0.65

the level of 90-day compressive strength of the specimens with CKD was the same as the

plain cement specimen. At a w/b ratio of 0.75, however, the concrete specimen with CKD

9 had a 35% reduction in compressive compared to the CKD 10 concrete and plain

cement specimens. Batis et al. (1996) concluded that concrete made with CKD 10 at 6%

replacement of PC 10 exhibited as good performance as the reference concrete. In

addition, the authors noted that the incorporation of CKD 10 reduced the porosity of

concrete from approximately 14% (reference) to 10%, as measured with mercury

intrusion porosimetry (MIP) at w/b ratios of 0.65 and 0.75 and after 6 months of exposure

in NaCl. It is widely accepted that a reduction in porosity improves compressive strength.

El-Sayed et al. (1991) conducted 28-day compressive strength tests on cement pastes

consisting of PC 11 and CKD 11. The CKD was blended at 0%, 3%, 5%, 6%, 7%, and

10% replacement of cement. The w/b ratio of pastes was 0.30. El-Sayed et al. (1991)

reported that as the percentage of CKD content in the paste increased, the compressive

strength measurements decreased. The authors also reported that up to 5% CKD

95

replacement of PC was within the range of the Egyptian Standard Specifications for

Ordinary and Rapid Hardening Cement (36 MPa).

Wang and Ramakrishnan (1990) investigated the compressive strength properties of

mortar and concrete made with a binary blend consisting of 5% CKD (CKD 12) and 95%

TIII cement (PC 12). The mortar mixes had a w/b ratio of 0.485 and were tested at 1, 3, 7,

14, 28, and 90 days. The authors reported that there was no significant difference in the

compressive strengths of CKD-PC mortar and plain PC mortar specimens. Most of the

CKD-PC mortar strengths fell within plus or minus 1.4% of the strength of plain PC

mortar. The concrete mixes were tested at w/b ratios of 0.45, 0.52, and 0.55 at 1, 3, 7, and

28 days. The authors stated that most of the strengths for CKD-PC concrete were 4%

higher in the earlier tests and 3.5% lower at 28 days than for plain cement concrete.

Ramakrishnan (1986) also used CKD 12 to determine whether it was suitable as a 5%

replacement of TI cement (PC 15). Mortar and concrete testing was conducted to assess

compressive strengths. The mortar mixes had a w/b ratio of 0.485 and were tested at 1, 3,

7, 14, 28, and 90 days. Ramakrishan (1986) noted that although the difference in strength

between blended and plain cement mortar cubes was very small, the blends with CKD

nearly always had the lower strength in comparison to the plain cement. Ramakrishan

(1986), therefore, stated that the mortar specimens showed that the CKD did not possess

any cementitious property. The concrete mixes were tested at a cement content of 386

kg/m3 and w/b ratio of 0.45. Six sets of each concrete mix were batched. The concrete

mixes were tested at 1, 3, 7, 28, and 90 days. As opposed to the mortar specimens, the

concrete with CKD had equal or higher compressive strengths than the plain concrete at

all ages of testing, with the exception of the compressive strengths at 28 days.

Ramakrishan (1986) therefore concluded that there was no significant difference in the

compressive strength of blended and cement concretes. The author did not explore the

reasons for the different impact of CKD on compressive strength between mortars and

concrete.

96

Bhatty (1986) used a TI cement (PC 16) with three different CKDs (CKD 13, CKD 14,

and CKD 15) to investigate their effect on compressive strength in mortars. The amount

of CKD in each blend was fixed at 10% by mass of PC with a w/b ratio of 0.45.

Compressive strengths were determined at 1, 7, 28, and 90 days, and one year. Bhatty

(1986) reported that the blends of cement and CKD at 10% partial replacement had

higher strengths at one day, but were generally lower at 7, 28, and 90 days in comparison

to cement alone. The strengths of mortars with CKD after one year, however, were

comparable to cement alone.

Bhatty (1985a) used the same CKD (CKD 13, CKD 14, and CKD 15) and cement (PC

16) as Bhatty (1986) to conduct paste compressive strength testing. Cement and CKD

blends were prepared by replacing 10% and 20% of cement and a w/b ratio of 0.45.

Compressive strengths were determined at 1, 7, 28, and 90 days, and one year. Bhatty

(1985a) stated that all blends with CKD had similar or higher strengths compared to

cement at one day, with CKD 14 blends producing much higher strengths compared to

cement and cement blends with CKD 13 and CKD 15. Blends with CKD 15 generally

showed significantly lower strengths at later ages compared to CKD 13 and CKD 14.

Bhatty (1985a) also noted that a significantly higher strength at one day was obtained for

the blend with 10% CKD 15 compared to that with 20% CKD 15, while the other blends

were quite comparable. From seven days to one year, blends made with 10% CKD

replacement generally showed higher strengths compared to blends with 20% CKD

replacement. This study showed that the strengths are adversely affected when high alkali

chloride (potassium chloride) CKD was used. Bhatty (1985a) observed that the higher

amounts of calcium carbonate in dusts appeared to be detrimental to strength

development, but higher free lime appeared to be beneficial for strength. Blends with

CKD containing higher amounts of sulfate developed higher strength compared to blends

made with CKD containing lower amounts of sulfate. Also, when sulfate was present in

97

the form of calcium sulfate (CKD 14), better strengths were obtained than when some of

the sulfate was also present in the form of alkali sulfates (CKD 13).

Bhatty (1984) also conducted compressive strength testing on pastes using five

companion cements and dusts obtained from five different cement plants. The five

companion cement kiln dust blends are: PC 17 and CKD 13, PC 18 and CKD 14, PC 19

and CKD 15, PC 20 and CKD 16, and PC 21 and CKD 17. For each CKD blend, the

CKD replacement of the PC was 0%, 10%, 15%, and 20% at a w/b ratio of 0.50. Bhatty

(1984) stated that at all ages, as the amount of CKD increased, the strength generally

decreased except with CKD 15, which consistently showed higher strength at 20%

addition compared to 10% and 15% addition levels. CKD 15 contained a much higher

chloride and alkali content and much lower sulfate content than the other CKDs. Bhatty

(1984) stated that alkali chlorides would probably behave similarly to calcium chloride,

and calcium chloride is known to increase concrete strength, especially at one to three

days curing. The author also reported that the strengths for blends containing CKD 15

were higher at one and seven days than at 28 and 90 days, when compared to cement at

the same ages. Also, strengths increased steadily with the increase in chloride level for

blends with CKD 15. The CKD-PC blends not containing CKD 15 decreased in strength

as the amount of CKD increased. This trend was more prominent in blends with CKD 16

and CKD 17, which contained moderate amounts of alkali and sulfates in the form of

alkali and calcium sulfates than in the blends with CKD 14 where the sulfate was

predominantly calcium sulfate. Bhatty (1984) concluded that the compressive strengths

for CKD blends containing 10%, 15%, and 20% were lower than cement alone. The

highest loss in strength occurred when CKDs with relatively high alkali and chloride

contents were used. However, as the amount of this CKD increased in the blend, the

strength also increased, likely due to an accelerating effect of alkali chlorides on

hydration.

98

Ravindrarajah (1982) used concrete mixes to study the compressive strength effect of

CKD 18 as a partial cement replacement of PC 22 at 1, 3, 7, 14, 28, 56, and 90 days.

Cement was partially replaced with CKD by mass at 0%, 15%, 25%, 35%, and 45%. The

total water content for each mix was different to produce a similar workability.

Ravindrarajah (1982) reported that as the percent of cement replaced by CKD increased

the compressive strength decreased, and the magnitude of strength reduction was

increased with the increase in CKD. The author cited four possible mechanisms to

explain the impact of CKD replacement of PC on compressive strength in these tests: (i)

alkalis in the CKD may modify the nature and strength of the cement hydration products,

(ii) since the CKD dust particles are finer than cement, the hydration of the cementitious

particles in the dust may occur at a faster rate than the PC. The author noted this by the

development of strength with age expressed as a percentage of its 28 day strength for the

control and CKD blended mixes. In general, the concrete with no CKD replacement

showed the lowest percentage of the 28-day strength at early ages when compared with

the CKD concrete, (iii) the portion of CKD that is not cementitious may act as a fine filler

and contribute to an increase in strength through increased compaction or provision of

nucleation sites for cement hydration, and (iv) concrete compressive strength is a

function of paste strength, aggregate strength, and aggregate-paste bond strength. The

presence of CKD causes the paste to become weaker, and as the paste strength weakens,

the aggregate-cement paste bond also weakens. Ravindrarajah (1982) concluded that

from his limited research, cement in concrete could be safely replaced by up to 15% of

CKD by mass from the perspective of short-term strength requirements.

99

A summary of the effects of studies conducted on compressive strength (f’c) with CKD-

PC blends compared to each of the respective reference plain cements is shown in Table

2.18. Although there were variations between researchers, generally the compressive

strength of samples with CKD was lower than those of the control cement samples. Some

of the suggested mechanisms for the reduction in strength are a reduction in the cement

content, an increase in the w/b ratio (for mixes that varied water to maintain the same

workability of all mixes), formation of portlandite, formation of chloro- and sulfo-

aluminate phases, higher porosity, lack of CKD cementitious value (low hydraulic

property), weakening of the paste-aggregate bond, and poor formation of C-S-H due to

alkalis from CKD. Some researchers reported that there was less of a decrease in

compressive strength between plain cement and CKD blends at lower w/b ratios. Some

researchers also noted that the CKD blends were higher at early ages and lower at later

ages than for plain cement. An appropriate alkalinity that increases the dissolution of

silicate species and formation of C-S-H and CKD acting as fine filler were suggested as

mechanisms that could cause an increase in the compressive strength of cement with

CKD as a partial substitute.

100

Table 2.18 Compressive strength: from CKD-PC literature review

Author(s)


General Effect on f’c


Maslehuddin et al. (2008b)

CKD 1/PC 1 CKD 1/PC 2

C N.R. 0,5,10,15 5% N.C 10-15% ↓


CKD 1/PC 3 M 0.485 0,5,10 ↑


CKD 2/PC 4 M V 0,2,4,6,8,10

↓

(1) Reduction in the cement content

(2) An increase in the w/b ratio

(3) Increase in free lime content in cement dust; the higher amount of Ca(OH)2 weakened the hardened matrix.

(4) The formation of chloro-and sulfoaluminate phases leads to the softening and expansion of the hydration products.

(5) The porosity increases due to the high chloride (7.5%) and sulfate (5.10%) content of the CKD (formation of these products enhances the crystallization of hydration products leading to an opening of the pore system).


CKD 3/PC 5 M C

V K

0,10,20,25,30 0,10,20,25,30

↓ ↓

(6) More decrease in compressive strength at higher w/b ratios

(7) CKD is not highly cementitious.


CKD 4/PC 6 C 0.65 0,20,40,60,80 ↓

P = Paste; M = Mortar; C = Concrete V = varied w/b ratio to maintain consistent workability K = constant w/b ratio, but more than one w/b ratio was tested N.C. = No Change f’c = compressive strength

101

Table 2.18 (continued) Compressive strength: from CKD-PC literature review

Author(s)




Wang et al. (2002)

CKD 5 / PC 7 M 0.50 0,15,25 15% ↑ 25% ↓

(8) Low hydraulic property of CKD causes the compressive strength to decrease.

(9) Increased strength of 15% CKD-PC blend may be attributed to an appropriate alkalinity that increases the dissolution of silicate species and formation of C-S-H.

(10) At 15% CKD replacement of PC, the reduction of volume fraction of pores larger than 3um may result in improved strength.

Shoaib et al. (1999)

CKD 6 / PC 8 C 0.50 0,10,20,30,40 ↓ (11) Loss of cement clinker which is mainly responsible for strength development

(12) CKD Cl- cause crystallization of hydration products resulting in opening of pore system of the hardened samples leading to strength loss

(13) Chloro-aluminate formation causes softening

(14) CKD alkalis cause the C-S-H phases to become heterogeneous & lowers strength

Batis et. al (1996)

CKD 9 / PC 10 CKD 10/ PC 10

C C

K K

0,6 0,6

↓ N.C.

(15) CKD 9 concrete specimen was same as control at w/b of 0.65, but at 0.75 was dramatically lower.

(16) CKD 10 concrete specimen had lower porosity (MIP) compared to the concrete specimen without CKD.

El-Sayed et al. (1991)

CKD 11 / PC 11

P

0.30 0, 3,4,5,6,7,10

↓


CKD 12/PC 12 M C

0.485 K

0,5 0,5

N.C. N.C.

(17) Most of the CKD concrete specimens were 4% higher at early ages and 3.5% lower at 28 days than for plain concrete specimens.

Ramakrishnan (1986)

CKD 12/PC 15 M C

0.485 0.45

0,5 0,5

↓ N.C.

(18) CKD does not possess any cementitious value.

Bhatty (1986)


M M M

0.45 0.45 0.45

0,10 0,10 0,10

1d ↑, rest ↓ 1d ↑, rest ↓ 1d ↑, rest ↓


102

Table 2.18 (continued) Compressive strength: from CKD-PC literature review

Author(s)




Bhatty (1985a)


P P P

0.45 0.45 0.45

0,10,20 0,10,20 0,10,20

1d ↑, rest ↑↓ 1d ↑, rest ↑↓ 1d ↑, rest ↑↓

(19) High alkali chloride (KCl) in CKD reduces f’c.

(20) High calcium carbonate in CKD reduces f’c.

(21) Higher free lime in CKD increases f’c.

(22) Blends with CKD containing higher amounts of sulfate developed higher strength compared to blends made with CKD containing lower amounts of sulfate.

(23) When sulfate was present in the form of calcium sulfate (CKD 14), better strengths were obtained than when some of the sulfate was also present in the form of alkali sulfates (CKD 13).

Bhatty (1984)


P P P P P

0.50 0.50 0.50 0.50 0.50

0,10,15,20 0,10,15,20 0,10,15,20 0,10,15,20 0,10,15,20

1d N.C., rest ↓

1d ↑, rest ↓ ↓

1d N.C., rest ↓ ↓

(24) Strengths increased steadily with increase in chloride level for blends with CKD 15.

(25) The CKD-PC blends not containing CKD 15 decreased in strength as the amount of CKD increased. This trend was more prominent in blends with CKD 16 and CKD 17 which contained moderate amounts of alkali and sulfates in the form of alkali and calcium sulfates than in the blends with CKD 14 where the sulfate was predominantly calcium sulfate.

(26) The highest loss in strength occurred when CKD with relatively high alkali and chloride contents were used. However, as the amount of this CKD increased in the blend, the strength also increased, likely due to an accelerating effect of alkali chlorides on hydration (acting similar to calcium chloride).


CKD 18/PC 22 C V

0,15,25,35,45

↓

(27) Alkalis may modify hydration products.

(28) CKD may act as a fine filler. (29) CKD presence weakens

paste and aggregate-paste bond.


103

2.5.6 Flexural and Tensile Strength

Al-Harthy et al. (2003) investigated the flexural strength effect of using CKD 3 as a

partial replacement of PC 5 using concrete. Al-Harthy et al. (2003) used seven different

concrete mixtures that were prepared using 0 (control), 5%, 10%, 15%, 20%, 25%, and

30% CKD 3 replacement by total mass of cement. For each mixture, three water-binder

ratios of 0.50, 0.60, and 0.70 by mass were used (the age at which the specimens were

tested was not specified but it is assumed that it was at 28 days). Flexural strength

measurements were determined using a two-point loading system. Toughness values,

which measure the ability of a material to absorb energy up to fracture, were calculated

based on the area under the stress-strain diagram. Similar to the effects on compressive

strength, the authors stated that the flexural strength and toughness values decreased with

an increase in CKD replacement for cement but at 5% and 10% replacement levels did

not have an appreciable adverse effect (especially at low w/b ratios). Al-Harthy et al.

(2003) attributed the reduction in flexural strength and toughness values to a reduction in

the cement content in the blends as the amount of CKD increased.

Udoeyo and Hyee (2002) studied the split tensile strength and modulus of rupture effects

of replacing PC 6 with CKD 4 at 20%, 40%, 60%, 80%, and 100% replacement in

concrete at a w/b ratio of 0.65. The tests were conducted at 1, 3, 7, and 28 days. Similar

to the results of compressive strength, Udoeyo and Hyee (2002) reported that the split

tensile strength and modulus of rupture decreased with an increase in CKD content. The

reduction in split tensile strength compared to the plain concrete was approximately 24%,

48%, 65%, and 90%, respectively, for concrete with the very high 20%, 40%, 60%, and

80% replacement levels of PC 6 with CKD 4. The reduction in modulus of rupture

compared to the plain concrete was approximately 18%, 70%, and 90%, respectively, for

concrete with 20%, 40%, and 60% replacement levels of PC 6 with CKD 4. Udoyeo and

Hyee (2002) did not suggest possible mechanisms for CKD-PC effects on split tensile

strength and modulus of rupture.

104

Wang et al. (2002) studied the effect of CKD 5 at partial replacement levels of PC 7 at

0%, 15%, and 25% on 28-day flexural strength with mortars at a w/b ratio of 0.50. Wang

et al. (2002) found that the flexural strength of blends with CKD and cement increase

with the CKD replacement of cement up to 15% (8.5 MPa) in comparison to cement

alone (8.2 MPa). The specimen with 25% CKD (7.6 MPa) had a much lower flexural

strength than the plain cement specimen. Wang et al. (2002) stated that the increased

strength in the specimen with 15% CKD may be attributed to an appropriate alkalinity

that increased the dissolution of silicate species and formation of C-S-H. Wang et al.

(2002) also reported that 15% CKD replacement of PC significantly reduced the volume

fraction of pores larger than 3 µm, which may result in improved strength.

Shoaib et al. (2000) conducted splitting tensile strength tests on concrete using CKD 6 as

a partial replacement of PC 8 at 0%, 10%, 20%, 30%, and 40% at a w/b ratio of 0.5. The

tests were conducted at one, three, and six months. The authors reported a gradual

decrease in the splitting tensile strength for all cylinders of concrete samples as the

amount of CKD increased. The reduction in tensile strength was attributed to the lower

bond strength between the aggregate and paste. Shoaib et al. (2000) stated that as the

amount of CKD increased in the paste, the bond strength between the aggregate and the

paste decreased.

Wang and Ramakrishnan (1990) studied the splitting tensile and flexural strength

properties of binary blends consisting of 5% CKD (CKD 12) and 95% Type III cement

(PC 12). The splitting tensile strength mortar mixes had a w/b ratio of 0.485 and were

tested at 1, 3, 7, 14, 28, and 90 days. The 14-day tensile strength of the CKD mortar was

10% higher than for the plain cement mortar. At 28 and 90 days, however, there was no

significant difference in the tensile strengths of the plain cement and CKD-PC specimens.

The flexural strength concrete mixes were tested at w/b ratios of 0.45, 0.52, and 0.55 at 1,

3, 7, and 28 days. Wang and Ramakrishnan (1990) stated that the results of flexure

strength tests of concrete specimens with CKD were within a range of ±4% of those of

105

the plain cement concrete and, therefore, not significant. Wang and Ramakrishnan (1990)

did not suggest possible mechanisms for CKD-PC effects on split tensile and flexural

strength.

Ramakrishnan (1986) studied the mortar splitting tensile and concrete flexural strength

properties made with a binary blend consisting of 5% CKD (CKD 12) and 95% TI

cement (PC 15). The splitting tensile strength mortar mixes had a w/b ratio of 0.485 and

were tested at 1, 3, 7, 14, 28, and 90 days. Ramakrishnan (1986) reported that for most of

the CKD-PC mortar splitting tensile strengths were lower than the corresponding plain

cement mortar strengths. The flexural strength concrete mixes were tested at a w/b ratio

of 0.45 at 1, 3, 7, and 28 days. Ramakrishnan (1986) reported no significant difference in

flexural strength between concretes containing CKD and plain concrete.

Ravindrarajah (1982) used concrete mixes to study the flexural and tensile strength

effects of CKD 18 as a partial cement replacement of PC 22 at 1, 3, 7, 14, 28, 56, and 90

days. Cement was partially replaced with CKD by mass at 0%, 15%, 25%, 35%, and

45%. The total water content for each mix was varied to produce similar workability.

Ravindrarajah (1982) also conducted tests to determine the flexural and tensile strengths.

As in the compressive strength test results, the flexural and tensile strengths decreased

with increased replacement of cement with CKD.

A summary of the studies conducted on the flexural and splitting tensile effects of CKD-

PC blends compared to the referenced plain cement is shown in Table 2.19. Generally,

the flexural and tensile strength effects of samples with CKD were lower than those of

the control cement samples, which is similar to the compressive strength effects. Many of

the suggested mechanisms for the reduction in flexural and split tensile strengths were the

same as the mechanisms for the reduction in compressive strength. The most commonly

suggested mechanism was the weakening of the aggregate-paste bond due to the presence

of CKD.

106

Table 2.19 Flexural and tensile strength: from CKD-PC literature review

Author(s)

Blend Type

w/b % CKD Replacement

General Effect on f’t



CKD 3/PC 5 C K 0,10,20,25,30

↓

(1) Reduction in the cement content.

(2) Less effect at low w/b ratios.


CKD 4/PC 6 C 0.65 0,20,40,60,80 ↓

Wang et al. (2002)

CKD 5/PC 7 M 0.50 0,15,25 15% ↑ 25% ↓

(3) Increased strength 15% CKD specimen may be attributed to an appropriate alkalinity that increased the dissolution of silicate species and formation of C-S-H.

(4) At 15% CKD replacement of PC, the reduction of volume fraction of pores larger than 3um may result in improved strength.

Shoaib et al. (1999)

CKD 6/ PC 8 C 0.50 0,10,20,30,40 ↓ (5) Weaker aggregate-paste bond as CKD content increases.


CKD 12/PC 12 M C

0.485 K

0,5 0,5

↑ N.C.

Ramakrishnan (1986)

CKD 12/PC 15 M C

0.485 0.45

0,5 0,5

↓ N.C.


CKD 18/PC 22 C V 0,15,25,35,45

↓

(6) Alkalis may modify hydration products.

(7) CKD may act as a fine filler. (8) CKD presence weakened paste

and aggregate-paste bond.

P = Paste; M = Mortar; C = Concrete. V = varied w/b ratio to maintain consistent workability f’t = flexural and/or tensile strength K = constant w/b ratio, but more than one w/b ratio was tested. N.C. = No Change

2.5.7 Volume Stability

2.5.7.1 Soundness

Maslehuddin et al. (2008a) studied the soundness effect of replacing PC 3 with CKD 1 at

0%, 5%, and 10% replacement by mass in pastes using autoclave expansion (ASTM

C151). The PC alone, PC with 5% CKD replacement, and PC with 10% CKD

replacement were 0.0075%, 0.0130%, and 0.3730%, respectively. Although the CKD-PC

blends had higher expansions than PC alone and increased as the percentage of CKD

replacement increased, the autoclave expansions were below the 0.80% allowed by

ASTM C150.

107

Bhatty (1986) used a Type I cement (PC 16) with three different CKD (CKD 13, CKD

14, and CKD 15) to investigate the effect on autoclave expansion (ASTM C151). The

amount of CKD in each paste was fixed at 10% by mass of PC, with a w/b ratio of 0.45.

Bhatty (1986) stated that the type of CKD used in the binary blend influenced the

autoclave expansion. Bhatty (1986) reported that the CKD-PC blend with CKD 14

showed autoclave expansion comparable to cement alone but higher expansions were

noted for CKD 13 and CKD 15. Bhatty (1986) also noted that each CKD-PC blend

autoclave expansion was well below the ASTM C150 specification of 0.80%. Bhatty

(1986) generally noted that when binary, ternary, and quaternary blends were made from

PC 16, the three different CKD, fly ash and slag – the blends containing CKD 15 (a high

chloride dust) generally produced higher autoclave expansions than blends with CKD 14,

which contained high sulfate.

Ravindrarajah (1982) used cement pastes to determine the soundness of PC-CKD blends

using the Le Chatelier apparatus (EN 196-3). PC 22 was partially replaced with CKD 18

by mass at 0%, 25%, 50%, 75%, and 100%. The total water content for each mix was

varied to produce similar workability. As the CKD percentage increased, so did the

expansion of the samples. This was attributed to the higher level of free lime in the CKD

in comparison to cement. Although the level of expansion was well within the range of

the British Standard, the expansion was much higher than that of cement.

A summary of the studies conducted on the soundness of CKD-PC blends compared to

each of the respective reference plain cements is shown in Table 2.20. High free lime,

sulfate, and chloride contents in the CKDs were attributed to the increased autoclave

expansions.

108

Table 2.20 Soundness: from CKD-PC literature review Author(s)


General Effect on Soundness



CKD 1/PC3 P V 0,5,10 ↓

Bhatty (1986)


P P P

0.45 0.45 0.45

0,10 0,10 0,10

↓ ↓ ↓

(1) High chloride CKD generally produced higher autoclave expansions than high sulfate CKD (includes mixes with slag, and fly ash).


CKD 18/PC 22 C V

0,15,25,35,45

↓

(2) High CKD free lime content.

P = Paste; M = Mortar; C = Concrete. V = varied w/b ratio to maintain consistent workability N.C. = No Change

2.5.7.2 Drying Shrinkage

Maslehuddin et al. (2008b) studied the drying shrinkage effect of replacing PC 1 (TI) and

PC 2 (TV) with CKD 1 at 0%, 5%, 10%, and 15% replacement by mass in concrete. The

drying shrinkage strain after 3, 7, 14, 28, 56, and 90 days of curing were tested, according

to ASTM C157. The drying shrinkage strain at the different percentage levels of CKD 1

replacement of PC 1 is shown in Figure 2.22. For PC 1, the highest shrinkage strain at all

ages was with the 15% CKD 1 concrete specimens followed by the concrete specimens

with 10% and 5% CKD 1, respectively. The 5% CKD 1 concrete specimens with PC 1,

however, were only marginally higher (<5%) than the concrete specimens without CKD

1. Although the test results were not provided for PC 2 concrete specimens, it was

reported that the initial shrinkage strain in the concrete specimens with CKD 1 was more

than that in the concrete specimens without CKD 1. After 90 days, however, the

shrinkage strain of 0%, 5%, and 10% concrete specimens with PC 2 was more or less

similar while that of 15% CKD 1 concrete specimens with PC 2 was significantly higher

than that of the other concrete specimens with PC 2.

109

Figure 2.22 Concrete drying shrinkage as a function of time at different replacement

levels of PC 1 with CKD 1 (Maslehuddin et al., 2008b)

Maslehuddin et al. (2008a) studied the drying shrinkage effect of replacing PC 3 with

CKD 1 at 0%, 5%, and 10% replacement by mass in mortars, according to ASTM C157.

The w/b ratio for each mortar mix was adjusted to maintain a constant flow. The w/b

ratios, however, were not reported. Drying shrinkage tests were conducted at 7, 14, 21,

28, 45, 60, and 75 days, as shown in Table 2.21. The drying shrinkage of mortar mixes

with 5% CKD ranged between 19% and 43% higher drying shrinkage than that of the

mortar mix with PC alone for the ages tested. The drying shrinkage of mortar mixes with

10% CKD ranged between 38% and 68% higher drying shrinkage than that of the mortar

mix with PC alone for the ages tested.

110

Table 2.21 Mortar drying shrinkage with 0%, 5%, and 10% CKD 1 replacement of PC 3

(Maslehuddin et al., 2008a)

Average drying shrinkage (%)

7 days 14 days 21 days 28 days 45 days 60 days 75 days

100% PC 3 0.0380 0.0528 0.0620 0.0694 0.0739 0.0811 0.0847

95% PC 3, 5% CKD 1 0.0481 0.0742 0.0886 0.0918 0.0942 0.0977 0.1008

90% PC 3, 10% CKD 1 0.0532 0.0889 0.0924 0.1043 0.1098 0.1144 0.1173

Wang and Ramakrishnan (1990) compared the drying shrinkage properties of concrete

made with a binary blend consisting of 5% CKD (CKD 12) and 95% TIII cement (PC

12). The concrete mixes were tested at w/b ratios of 0.45 and 0.52 and the drying

shrinkage results are shown in Figure 2.23. The authors reported no significant difference

in drying shrinkage between the concrete mixes at w/b of 0.45. At 0.52 w/b ratio,

however, the concrete mix with CKD had considerably higher (22%) drying shrinkage

than the plain cement concrete. Wang and Ramakrishnan (1990) stated they did not know

the reason for this difference.

111

Figure 2.23 Concrete drying shrinkage as a function of time at two different w/b ratios

with 5% CKD 12 replacement of PC 12 (Wang and Ramakrishnan, 1990)

Ramakrishnan (1986) also used CKD 12 to determine whether it was suitable as a 5%

replacement of TI cement (PC 15). Concrete testing was conducted to assess drying

shrinkage at a w/b ratio of 0.45. Ramakrishnan (1986) reported that the shrinkage

deformation for CKD concrete mixes was a little more than that of the plain cement

concrete.

Bhatty (1986) used a Type I cement (PC 16) with three different CKDs (CKD 13, CKD

14, and CKD 15) to investigate their effect on drying shrinkage in mortars. The amount

of CKD in each blend was fixed at 10% by mass with a w/b ratio of 0.45. Drying

shrinkage tests were conducted at 4, 11, 18, and 25 days. For all blends containing CKD

13 and CKD 15 the drying shrinkage increased compared to cement alone. The blends

containing the high sulfate CKD 14, however, showed lower shrinkage than cement

alone. Bhatty (1986) concluded that the drying shrinkage of binary blends with high

sulfate CKD was lower than cement alone or other binary blends with low sulfate CKD.

Mix 2: w/b = 0.52

Mix 3: w/b = 0.45

112

A summary of the studies conducted on the drying shrinkage effects of CKD-PC blends

compared to each of the respective reference plain cements is shown in Table 2.22. It

appears that adverse effects on drying shrinkage of CKD-PC blends may be more

significant at higher w/b ratios. Bhatty (1986) stated that drying shrinkage of CKD-PC

blends with high sulfate content was lower than the control and other lower sulfate CKD-

PC blends. This was not expected since higher sulfate levels are typically associated with

drying shrinkage expansion. One possible explanation is that the high sulfate CKD may

have contained less soluble sulfate forms than the PC it replaced and the other CKDs.

Table 2.22 Drying shrinkage: from CKD-PC literature review

Author(s)


General Effect on Drying Shrinkage




C N.R. 0,5,10, 15 5% N.C. 10-15% ↑


CKD 1/PC 3 M V 0,5,10 ↑


CKD 12/PC 12 C C

0.45 0.52

0,5 0,5

N.C. ↑

(1) Higher drying shrinkage at higher w/b ratio.

Ramakrishnan (1986)

CKD 12/PC 15 C 0.45 0,5

↑

Bhatty (1986)


M M M

0.45 0.45 0.45

0,10 0,10 0,10

↑ ↓ ↑

(2) Drying shrinkage of binary blends with high sulfate CKD was lower than cement alone and other binary blends with low sulfate CKD

P = Paste; M = Mortar; C = Concrete. N.C. = No Change V = Varied w/b ratio to maintain consistent workability

2.5.7.3 Volume Stability Summary

The volume stability of CKD blends in the literature review was assessed by considering

the results of soundness and drying shrinkage. Three researchers reported that as the

CKD increased, the autoclave expansion also increased for all five of the CKD-PC

blends. One mechanism for this effect was suggested to be related to the high free lime

content of CKD. It was also reported that high chloride CKD generally produced higher

autoclave expansions than high sulfate CKD. Five researchers reported on drying

113

shrinkage. At 5 % CKD replacement, two CKD-PC blends had no change in drying

shrinkage while four other CKD-PC blends had higher drying shrinkage values compared

to the control cements. At 10% CKD replacement, five of the six CKD-PC blends had

increased drying shrinkage compared to the control cements. The CKD-PC blend that

decreased drying shrinkage was a high sulfate CKD, but it is likely that this CKD

contained less soluble forms of sulfate than the PC or the other CKDs. At 15 % CKD

replacement, the drying shrinkage values of the two CKD-PC blends were higher than

that at 10% CKD replacement. It was noted that higher drying shrinkage occurred at

higher w/b ratio.

2.5.8 Durability

2.5.8.1 Alkali-Aggregate Reaction

Bhatty (1986) used a Type I cement (PC 16) with three different CKDs (CKD 13, CKD

14, and CKD 15) in mortars to investigate their effect on alkali-aggregate reactivity

(AAR) according to ASTM C227. The aggregate used consisted of 95% Ottawa sand

(non-reactive aggregate) and 5% Beltane Opal (reactive aggregate). Opal contains

reactive silica that is used to assess the contribution of hydroxyl ions from the binder to

form ASR. In this test method, the mortar specimen bars are stored vertically in a sealed

environment above water, which is at the bottom of the container. The amount of CKD in

each blend was fixed at 10% by mass of PC with a w/b ratio of 0.45. The expansion

measurements were taken at 3 and 6 months. PC 16 contains a total alkali content of

0.53% as sodium oxide equivalent and is considered a low alkali cement according to

ASTM C150. The blends with CKD 13, CKD 14, and CKD 15, had total alkali contents

of 0.67%, 0.66%, and 0.82%, respectively. The expansions of CKD-PC blends at three

and six months were very similar to cement alone and significantly below the ASTM

limit of 0.1% at six months.

Bhatty (1985b) also conducted mortar bar expansion tests using four companion cements

and dusts obtained from four different cement plants to assess potential alkali-aggregate

114

reactivity using ASTM C227. The w/b ratio was 0.50 and measurements were taken

periodically over a one-year period. The four companion cement kiln dust blends are: PC

17 and CKD 13, PC 18 and CKD 14, PC 19 and CKD 15, and PC 20 and CKD 16. Each

CKD replacement of PC was at 0%, 10%, 15%, and 20%. Although the PCs and CKDs

from individual plants showed significant differences, all CKD blends exhibited higher

ASR induced expansions compared to the control PC alone. As the amount of CKD in the

blends increased, expansion also increased. Bhatty (1985b) stated that at six months the

highest expansion obtained was with CKD 16 blends while the lowest expansion was

obtained using CKD 13. Blends with CKD 15 produced lower expansions despite having

the same alkali contents as blends containing CKD 16. This is likely due to the fact that a

major portion of the alkali in CKD 15 is present as a chloride salt. CKD 14 blends had

similar water soluble alkali content to blends made with CKD 13 but showed much

higher expansion compared to the latter. Differences in expansion of blends containing

similar alkali contents can be attributed to the difference in chemical composition of

cements and dusts and to the type of alkali compounds present in these materials. Water

soluble alkali showed a more meaningful relationship with expansion than did total alkali

with respect to the 0.60% alkali limit for CKD-PC blends. The author concluded that kiln

dust is not the only material in a binary blend that can influence alkali-aggregate

expansion. Different cements with the same kiln dust can produce different expansion not

only due to differences in alkali content but also in other compositional variations.

A summary of the studies conducted on the alkali-aggregate reactivity of CKD-PC blends

compared to each of the respective reference plain cements is shown in Table 2.23.

115

Table 2.23 Alkali-aggregate reactivity: from CKD-PC literature review Author(s)


General Effect on AAR


Bhatty (1986)


M M M

0.45 0.45 0.45

0,10 0,10 0,10

N.C. N.C. N.C.

Bhatty (1985b)

CKD 13/PC 17 CKD 14/PC 18 CKD 15/PC 19 CKD 16/PC 20

M M M M

0.50 0.50 0.50 0.50

0,10,15,20 0,10,15,20 0,10,15,20 0,10,15,20

↑ ↑ ↑ ↑

(1) As the amount of CKD in the blends increased, expansion also increased.

(2) Water soluble alkali showed a more meaningful relationship with expansion than did total alkali with respect to 0.60% alkali limit for CKD-PC blends.

(3) Blends with CKD 15 produced lower expansion despite having the same alkali contents as blends containing CKD 16. This is likely due to the fact that a major portion of the alkali in CKD 15 is present as a chloride salt.

(4) CKD 14 blends had similar water soluble alkali content to blends made with CKD 13 but showed much higher expansion compared to the latter.

(5) Differences in expansion of blends containing similar alkali contents can be attributed to the difference in chemical composition of cements and dusts and to the type of alkali compounds present in these materials.

(6) CKD is not the only material in a binary blend that can influence alkali-aggregate expansion. Different cements with the same kiln dust can produce different expansion not only due to differences in alkali content but other compositional variations as well

P = Paste; M = Mortar; C = Concrete N.C. = No Change.

116

2.5.8.2 Steel Corrosion

Maslehuddin et al. (2008b) studied the electrical resistivity effect of replacing PC 1 (Type

I) and PC 2 (Type V) with CKD 1 at 0%, 5%, 10%, and 15% replacement by mass in

concrete. Since electrical resistivity is a function of moisture content in the concrete,

resistance measurements were conducted at varying water content in the specimens. The

specimen was initially saturated in water for 28 days and afterward the electrical

resistivity was measured. The specimen was then allowed to dry and the electrical

resistivity measurements were taken periodically. Ultimately, the specimen was oven-

dried at 110°C and the moisture content determined. The electrical resistivity after 28

days (water curing) at the different percentage levels of CKD 1 replacement of PC 1 and

PC 2 was plotted against the moisture content, as shown in Figure 2.24. The electrical

resistivity decreased with increasing moisture content. The authors reported that the

electrical resistivity of PC 1 concrete mixes with CKD 1 at 0%, 5%, and 10% was not

significantly different. However, there was a significant decrease in electrical resistivity

of PC 1 concrete mixes with CKD 1 at 15%. For PC 2, the electrical resistivity decreased

significantly for all concrete specimens with CKD, in comparison to the concrete

specimens without CKD. The authors suggested that the decrease in electrical resistivity

due to the partial substitution of CKD 1 for PC2 in the concrete specimens may be

attributed to an increase in free chloride ions. The higher presence of free chloride ions in

PC2 concrete specimens with CKD in comparison to PC 1 concrete specimens with CKD

is possibly due to PC 2 having low-chloride binding properties (lower C3A content)

compared to PC 1. The authors used an electrical resistivity classification system to

assess the risk of reinforcement corrosion, as shown in Table 2.24. At a moisture content

of approximately 3%, the electrical resistivity of PC 1 and PC 2 concrete specimens with

and without CKD was in the range of approximately 25 – 50 kΩ.cm. Therefore,

according to Table 2.24, at approximately 3% moisture content the risk of steel

reinforcement corrosion for all of the concrete specimens is of moderate intensity.

117

(a)

(b)

Figure 2.24 Concrete specimen variation of electrical resistivity with moisture content at

different percentage levels of CKD 1 replacement of (a) PC 1 and (b) PC 2 (Maslehuddin

et al., 2008b)

118

Table 2.24 Concrete resistivity and risk of reinforcement corrosion as specified in COST

509 (Maslehuddin et al., 2008b)

Concrete resistivity (kΩ cm) Risk of reinforcement corrosion

<10 High

10-50 Moderate

50-100 Low

>100 Negligible

Konsta-Gdoutos et al. (2001) completed corrosion tests on mortar specimens using CKD

5 as a partial replacement of PC 7 at 0%, 15%, and 25% by mass. The mortar w/b ratio

was 0.50 and was mixed in accordance with EN 196-1. Mortar specimens of 75 x 75 x

300 mm were prepared and reinforced centrally with a 12M steel bar and a 12.7 mm

cover. They were cured for seven days in a curing room. To accelerate corrosion of the

embedded steel the specimens were immersed half way in a 5% (by mass) NaCl solution.

The results were interpreted according to ASTM C876 criteria for corrosion of steel in

concrete. The corrosion potential of the binary blends was monitored three times per

week. The half cell potential technique was used to measure the risk of corrosion. The

corrosion potentials observed for the CKD-PC blends suggest that more than 15% CKD

replacement of PC accelerates corrosion. This is possibly due to the introduction of

chloride ions in the mix incorporated in the CKD.

Batis et al. (1996) used PC 7 and 2 CKDs (CKD 8 and CKD 9) for testing steel corrosion

of concrete containing CKD. Each CKD was added as a 6% partial cement replacement

at three w/b ratios: 0.50, 0.65, and 0.75. Each concrete test specimen was reinforced with

steel bars and immersed in 3.5% by mass NaCl solution 5 cm from their bottom. The free

upper section of rebars were connected to copper cable and covered with epoxy resin.

The corrosion potential was measured every seven days. Batis et al. (1996) reported that

119

the blends with CKD 9 had improved corrosion resistance in comparison to the reference

mix. The blends with CKD 8 had reduced corrosion resistance in comparison to the

reference mix. The protective behavior of CKD 9 against corrosion is attributed to its

fineness and relatively higher alkalinity. Batis et al. (1996) also noted that CKD 8 had

double the chloride content and three times higher sulfate content compared to CKD 9.

The elevated chloride and sulfate ion contents accelerated the corrosion rate in the

concrete specimens made with CKD 8 at all w/b ratios.

El-Sayed et al. (1991) conducted steel corrosion tests on cement pastes and mortars

consisting of PC 11 and CKD 11. The tests were used to determine the potential level of

CKD replacement in pastes and mortars without impairing the passivity of the embedded

steel. The CKD was blended at 0%, 3%, 5%, 6%, 7%, and 10% replacement of cement.

The w/b ratio was 0.30 for pastes and 0.60 for mortars. For both pastes and mortars, as

the amount of CKD increased the passivity of steel decreased. El-Sayed et al. (1991)

determined that the steel passivity was maintained at an acceptable level up to 5% CKD

by mass of cement. The authors attributed the 5% CKD level of corrosion protection

from aggressive sulfate and chloride ions in the mix to the high hydroxide (OH-) content

that develops during hydration as a result of the CKD. El Sayed et al. (1991) concluded

that the OH- helped in maintaining the passive oxide layer that protected the steel.

A summary of the studies conducted on the steel corrosion of CKD-PC blends compared

to each of the respective reference plain cement is shown in Table 2.25.

120

Table 2.25 Steel corrosion: from CKD-PC literature review Author(s)


General Effect on Steel

Corrosion




C N.R. 0,5,10,15 ↑ (1) Decrease in electrical resistivity (higher risk of steel reinforcement corrosion) may be due to presence of free chloride ions from CKD

Konst-Gdoutos et al. (2001)

CKD 5/PC 7 M 0.50 0,15,25 ↑ (2) More than 15% CKD replacement of PC accelerated corrosion possibly due to the introduction of CKD chloride ions.

Batis et. al (1996)

CKD 9 / PC 10 CKD 10/ PC 10

C C

K K

0,6 0,6

↑ ↓

(3) Protective behavior of CKD 10 against corrosion was partially attributed to its higher fineness.

(4) Protective behavior of CKD 10 was partially attributed to its relatively higher alkalinity.

(5) CKD 9 had elevated chloride and sulfate ion contents (compared to CKD 10) – accelerated the corrosion rate.

El-Sayed et al. (1991)

CKD 11/ PC 11

P M

0.30 0.60

0,3,4,5,6,7,10 0,3,4,5,6,7,10

↑ ↑

(6) Corrosion protection from aggressive sulfate and chloride ions in the mix was attributed to the high hydroxide (OH-) content that developed during hydration as a result of the CKD. The OH- helped in maintaining the passivation film that protected the steel.

P = Paste; M = Mortar; C = Concrete. K = constant w/b ratio, but more than one w/b ratio was tesed. N.R. = Not Reported

121

2.5.8.3 Permeability

Maslehuddin et al. (2008b) studied the chloride permeability effect of replacing PC 1

(Type I) and PC 2 (Type V) with CKD 1 at 0%, 5%, 10%, and 15% replacement by mass

in concrete, as shown in Table 2.26. The chloride permeability was measured after 28

days of curing, according to ASTM C1202. The measure of chloride permeability (values

in Coulombs) increased with an increase in the CKD replacement of PC. At 5% CKD

replacement, the increase in coulomb measurement increased by 6% for PC 1 and 1% for

PC 2. At 10% CKD replacement, the increase in coulomb measurement increased by

16% for PC 1 and 13% for PC 2. At 15% CKD replacement, the increase in coulomb

measurement increased by 62% for PC 1 and 23% for PC 2. As per ASTM C1202, the

PC 1 concrete specimens with 0%, 5%, and 10% CKD were within the low range for

chloride permeability while the 15% CKD was in the moderate range. The chloride

permeability of the PC 2 concrete specimens with and without CKD replacement was in

the moderate chloride permeability classification. The author suggested that the increased

chloride content of the CKD may lead to a decrease in the electrical resistivity of

concrete which is reflected in an increase in chloride permeability. As the content of

CKD increases, more free chloride ions are liberated and cause the measure of chloride

permeability to increase.

122

Table 2.26 Chloride permeability of PC 1 and PC 2 with CKD 1 replacement at 0%, 5%,

10%, and 15% (Maslehuddin et al., 2008b)

Al-Harthy et al. (2003) used sorptivity (a measure of the capacity to absorb) and the

initial surface absorption test (ISAT) to measure the permeability characteristics of

different mortar samples containing CKD. Durability of mortar and concrete largely

depends on the ease with which fluids can enter and move through the material,

commonly known as permeability. Mixtures were prepared using CKD 3 at 0%, 10%,

20%, 25%, and 30% replacement level of PC 5 by mass. Al-Harthy et al. (2003)

gradually added water to each mix to maintain the same workability. Al-Harthy et al.

(2003) stated that the sorptivity and ISAT measurements both showed that the sorptivity

of mortar decreased with incorporation of CKD in the mortar mixtures. They further

noted that since sorptivity is a function of mixture strength, the higher the strength the

lower the sorptivity values. The use of CKD improved absorption properties and

therefore, can enhance durability. The authors attributed the lower sorptivity values to the

very fine particles of CKD, but did not elaborate on the nature of this mechanism. It is

assumed that the very fine particles could provide nucleation sites for enhanced cement

hydration and/or act as fine filler material between the cement grains.

A summary of the study conducted on the steel permeability effects of CKD-PC blends

compared to the respective reference plain cement is shown in Table 2.27.

123

Table 2.27 Permeability: from CKD-PC literature review

Author(s)


General Effect on

Permeability




C N.R. 0,5,10,15 ↑

(1) Increase in coulomb measured permeability may be due to presence of free chloride ions from CKD


CKD 3/PC 5 M

V

0,10,20,25,30

↓ (2) Very fine particles of CKD.

P = Paste; M = Mortar; C = Concrete. V = varied w/b ratio to maintain consistent workability. N.R. = Not Reported

2.5.8.4 Freezing and Thawing

Batis et al. (1996) used PC 10 and two CKDs (CKD 9 and CKD 10) to study rapid

freezing and thawing resistance of concrete containing CKD. Each CKD was added as a

6% partial cement replacement at three w/b ratios: 0.50, 0.65, and 0.75. The concrete test

specimens were placed in a freezing and thawing test chamber and exposed to a

continuous 24-cycle with the following conditions: from 35ºC to -35ºC in three hours,

after that the temperature was kept constant at -35ºC for 3 hours, then it increased to 35ºC

at which it stayed for 1 hour. Each complete cycle lasted eight hours for a total of three

times per day. The mass loss of the specimens was measured at regular intervals of about

once per week. According to ASTM C666 (rapid freezing and thawing in water),

completion was defined at 300 cycles or when the average of percentage mass loss

exceeded 25% (whichever came first). Batis et al. (1996) reported that the CKD 10

concrete specimens had similar mass loss behaviour compared to the reference concrete

specimens at all three w/b ratios. The 6% CKD 9 concrete specimens had significantly

less resistance to rapid freezing and thawing compared to the reference concrete

specimens at all three w/b ratios.

124

Wang and Ramakrishnan (1990) conducted studies on the freezing and thawing

performance of concrete made with a binary blend consisting of 5% CKD (CKD 12) and

95% TIII cement (PC 12). The concrete mixes were tested at w/b ratios of 0.45, 0.52, and

0.55. Freezing and thawing performance was evaluated using two sets of two specimens

for each type of mix. One set was exposed to the conditions specified in ASTM C666

while the other was used as a reference. In addition to monitoring changes in fundamental

transverse frequency to calculate durability factors, changes in length and mass were also

recorded. Wang and Ramakrishnan (1990) concluded that the concrete specimens with

CKD did not show inferior resistance to rapid freezing and thawing in up to 120 cycles

(84 days), but experienced a little more mass loss thereafter compared to the plain cement

concrete specimens.

Ramakrishnan and Balaguru (1987) conducted an experimental investigation on the

freezing and thawing durability of concretes in which 5% of the cement was replaced

with CKD 11. Three types of cement were assessed: Type I (PC 15), Type II (PC 13), and

TIII (PC 14). Six sets of concrete with cement contents of 386 kg/m3 and 332 kg/m3 were

tested. The w/b ratio was 0.45 for the higher cement content and 0.52 for the lower

cement content. The air content ranged from 3.1 – 8.4%. The freezing and thawing tests

were conducted according to ASTM C666, using 100 x 100 x 375 mm prisms. Mass loss,

fundamental resonant transverse, frequency, and pulse velocity were measured at

approximate intervals of 30 cycles. The freezing and thawing tests were stopped at 300

cycles. Ramakrishnan and Balaguru (1987) concluded that under freezing and thawing

conditions, kiln dust (5% by mass) incorporated behavior is essentially similar to that of

plain PC concretes.

A summary of the studies conducted on the freezing and thawing effects of CKD-PC

blends compared to each of the respective reference plain cement is shown in Table 2.28.

125

Table 2.28 Freezing and thawing cycles: from CKD-PC literature review

Author(s)


General Effect on Freezing and

Thawing Deterioration


Batis et. al (1996)

CKD 9 / PC 10 CKD 10/ PC 10

C C

K K

0,6 0,6

↑ N.C.


CKD 12/PC 12 C K 0,5 <120 cycles N.C. >120 cycles ↑

Ramakrishnan and Balaguru (1987)


C C C

K K K

0,5 0,5 0,5

N.C. N.C. N.C.

P = Paste; M = Mortar; C = Concrete. V = varied w/b ratio to maintain consistent workability K = constant w/b ratio, but more than one w/b ratio was tested.

2.5.8.5 External Sulfate Resistance

Bhatty (1986) used a TI cement (PC 16) with three different CKDs (CKD 13, CKD 14,

and CKD 15) in mortars to investigate their effect on sulfate resistance (ASTM C1012).

The amount of CKD in each blend was fixed at 10% by mass of PC, with a w/b ratio of

0.45. Bhatty (1986) reported that the blends containing cement and CKD resulted in

expansions that were lower than cement alone. The author did not provide an explanation

for the improved sulfate resistance of the CKD blend. Improved sulfate resistance,

however, is often a result of lower permeability.

A summary of the study conducted on the external sulfate resistance effects of CKD-PC

blends compared to each of the respective reference plain cement is shown in Table 2.29.

Table 2.29 Sulfate resistance: from CKD-PC literature review

Author(s)

Blend Type w/b % Replacement Level

General Effect on External

Sulfate Resistance


Bhatty (1986)


M M M

0.45 0.45 0.45

0,10 0,10 0,10

↑ ↑ ↑

P = Paste; M = Mortar; C = Concrete.

126

2.5.8.6 Durability Summary

Although there are relatively few studies on CKD-PC blend durability, researchers have

stated the need to consider potential issues due to the composition of CKD (Wang et al.,

2002; Dyer et al., 1999). Since CKD is typically high in sulfur, alkalis, and chlorides,

there is the potential for external sulfate expansion, AAR, and steel corrosion. The impact

of using CKDs as a substitute of PC on microstructure and air content could affect

permeability and resistance to freezing and thawing cycles. One study on AAR reported a

potential increase for AAR using CKDs, while another study reported no impact.

Differences in expansion of CKD blends with similar alkali contents indicates that factors

other than alkali content – such as the type of alkali compound and/or the CKD-PC

chemical composition – can play a role in AAR. Steel corrosion increased as the amount

of CKD increased. A major contributor to steel corrosion can be the high chloride content

of CKD. The high alkali content of CKD, however, can help in maintaining the high

passivation film layer that protects steel. One study reported that permeability was

reduced with CKD, likely due to the presence of fine particles. Lower permeability

indicates higher durability. Three studies using blends with 5% and 6% CKD

replacement of PC reported no impact in four blends and increased mass loss in two

blends when exposed to freezing and thawing cycles. One study showed that CKD blends

improve resistance to external sulfate attack. Possible explanations for the freezing and

thawing and sulfate resistance effects of CKD blends were not provided.

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3.0 MATERIALS AND EXPERIMENTAL DETAILS

This thesis consists of several experiments that were designed to provide data within the

context of two main objectives:

1. Investigate the characterization of CKDs using chemical, physical, mineralogical,

and dissolution analytical techniques

2. Establish an improved understanding of the effects of CKDs as partial substitution

for PC on:

a. heat of hydration

b. normal consistency

c. initial set time

d. compressive strength

e. expansion in limewater

f. soundness

g. ASR.

3.1 Materials

The materials used in this study were seven different CKDs (identified as A, B, C, D, D*,

E, and F) having a wide range of chemical/mineralogical and physical properties based

on different raw material sources and technologies, two filler materials (limestone

powder and ground silica), and two PCs of high and low alkali content (Cements TI and

TII, respectively). Each PC consists of only clinker and gypsum (pure PC). Limestone

powder (LS) and ground silica (inert) (SLX) were selected for comparison to the CKDs,

based on similar Blaine fineness.

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All CKDs were fresh, as opposed to coming from a stockpile or landfill. The CKDs in

this study were selected to provide a representation of available CKDs in North America

from the three major types of cement manufacturing processes: wet, long-dry, and

preheater/precalciner, as shown in Table 3.1. The CKDs are from different cement plants

except CKDs D and D*, which are from the same plant. Only one sample from each

cement plant was planned but due to the uncharacteristically low Blaine fineness value of

the original sample (CKD D*), a second sample was collected (CKD D).

Table 3.1 CKD kiln process description

CKDs Kiln Process Dust Collection System

A Wet Electrostatic Precipitator

B Wet Bag-house

C Long-dry Electrostatic Precipitator

D, D* Long-dry Bag-house

E Precalciner (By-pass) Electrostatic Precipitator

F Precalciner (By-pass) Electrostatic Precipitator

Due to the length of the study, all materials were stored in plastic bags that were placed in

airtight plastic pails between uses. LOI was performed on all materials periodically to

ensure that (i) no moisture had been absorbed and (ii) they had not carbonated. LOI

results indicated that the materials did not change over time.

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3.2 Testing of Raw Materials


The chemical compositions of the PCs were determined in accordance with ASTM C114.

X-ray fluorescence (XRF) was used to determine the major elements likely to be present

in PC, with the exception of moisture and carbon dioxide (CO2). The samples were de-

carbonized prior to XRF analysis using LOI. The LOI required igniting the dried sample

to a constant mass in a muffle furnace at 950 ± 50˚C in an uncovered porcelain crucible.

After the PCs had reached constant mass (in approximately 1 hour), samples were

prepared as fused beads using lithium borate. Fused beads were prepared by dissolving

the specimen in lithium borate at a high temperature (>1000˚C). Then the fused bead

samples were placed in the XRF spectrometer to determine the major elements. The

alkali, sulfate, and chloride contents for PCs from the XRF analysis were validated using

flame photometry, induction heating (LECO SC-432 Sulfur Analyzer), and

potentiometric titration. Water soluble alkali content was determined according to ASTM

C114. One gram of material is put in contact with water for 10 minutes and, after

filtration, the amount of water soluble alkalis contained in the aliquot was determined by

flame photometry. Some testing procedures developed for PC were modified to

accurately determine the chemical composition of the CKDs; these are described in

Section 4.1.1.


The free lime (free calcium oxide) test that is designed for PC (ASTM C114) using hot

benzoic acid titration was used for each PC and CKD. Mineralogical characterization of

all materials included X-ray diffraction (XRD) and thermal analyses. XRD was

performed with a Rigaku D/MAX 2000 diffractometer on pressed powder samples,

except CKD D, which was analyzed using PANalytical’s X’Pert PRO. Scanning was

performed in the range of 5º ≤ 2θ ≤ 65º with a scan rate of 0.02º 2θ per second. Powder

samples were analyzed using standard monochromatic CuKά radiation generated at

20mA and 40 kV. PC gypsum phases were obtained by differential scanning conduction

130

calorimetry (DSC) using the Mettler TA3000 System. CKD samples were analyzed by

thermo gravimetric analysis (TGA) in a nitrogen environment using a Netzsch STA 730

thermal analysis apparatus at a heating rate of 10˚C/minute.


The relative density of each material was obtained by air-comparison pycnometer. The

relative density of the material is a required input in the calculation to determine the

Blaine fineness. The Blaine air permeability test (ASTM C204) and the percentage of

material finer than 45 µm (No. 325) sieve (ASTM C430) were used to determine the

fineness of all materials in this research program. The Blaine fineness test is the most

widely used method to assess the fineness of PC. The Blaine fineness test indirectly

measures the surface area of the cement particles per unit mass. Particle size distribution

(PSD) of all materials was also determined using the Malvern laser diffraction particle

sizer, 2600 Series. Although there is presently no standard specification for determining

the particle size distribution of PC, the cement industry commonly uses this test method

to determine fineness of materials. The usual procedures for measuring PC fineness were

slightly modified to accurately measure the fineness of the CKDs and fillers; these are

discussed in Section 4.1.3.

3.2.4 Dilute Stirred Suspensions

Dilute stirred suspensions were performed on each PC and CKD. A sample of each

material was mixed with water in a glass beaker with a water to solid ratio of 10. Each

mixture was stirred vigorously for 10 minutes by hand with a glass rod and the

temperature of the solution was maintained at approximately 23ºC. The solid material

was then separated using a vacuum filter. The liquid solution was placed in a sample tube

for analysis. Hyroxyl ion concentration was measured immediately for each sample. Then

the solution filtrate was brought to a pH of less than two using nitric acid. The purpose of

adjusting the sample pH to less than two was to minimize metal cation precipitation and

adsorption onto the sample container wall. It is known that nitric acid can also cause

131

certain elements from glass ampoules to become soluble. Therefore, appropriate plastic

ampoules were used to collect the samples. The balance of the cation and sulfide ionic

concentrations of each solution was determined by using Inductively Coupled Plasma

Atomic Emission Spectrometry (ICP AES) directly; the model used was the Perkin Elmer

Model Optima 3000DV ICP AEOS. The chloride ion concentration was approximated

using the U.S. Geological Survey public domain PHREEQC geochemical software

package.

3.3 CKD-PC Blends

For paste and mortar tests, the amount of CKD (CKD A, B, C, D, E, or F), limestone

powder, or silica flour in each blend was either 10% or 20% replacement of PC, by mass.

This resulted in 30 binder blends: 2 PC binder blends, 24 CKD-PC binder blends, and 4

PC-filler binder blends. All materials were sieved on a No. 20 sieve and weighed

accurately. Each blend was then homogenized by hand with a large spoon in a steel bowl

prior to the addition of water and/or fine aggregate (mortar sand). The paste and mortar

tests used in this study are described in Sections 3.3.1 to 3.3.7.

For concrete tests, the amount of CKD ranged between 7% and 13% replacement of PC,

by mass. CKD D was not available at the time of concrete casting, so the low Blaine

fineness CKD D* was used. The concrete CKD-PC blend tests are described in further

detail in Section 3.3.8.

3.3.1 Heat of Hydration

PC hydration leads to the evolution of heat and, consequently, isothermal conduction

calorimetry is commonly used to assess hydration kinetics of different paste blends. In

this study, the TAM Air isothermal conduction calorimeter was used to determine the

effects of the CKDs and fillers on the early hydration characteristics of the blends in

accordance with ASTM C1679. Eight samples can be analyzed at a time and an air

thermostat is used to maintain the isothermal temperature, which can be set between 15

132

and 60°C. The TAM Air utilizes heat conduction to transfer heat away from the sample

to a heat sink to keep the sample temperature essentially constant. The flow of heat,

caused by the temperature gradient across the sensor, creates a voltage signal

proportional to the heat flow. The heat output is calibrated by measuring the output from

a known heat source under identical conditions to the hydrating material. To minimize

disturbances from outside the calorimeter, an inert reference sample is used. The inert

sample is placed on a parallel heat flow sensor. Any external disturbances will influence

both the sample and the inert sample identically and be nullified. The detection limit of

the TAM AIR is 2 µW and the precision is specified to be ±10 µW. The time constant is

approximately 100 seconds. The results can be presented as either differential plots

showing the rate of heat evolution as a function of time or integral plots showing the total

amount of heat liberated as a function of time.

All materials were stored in tightly sealed plastic bags inside containers at a constant

temperature of 23 ± 2°C to pre-condition them prior to testing. Paste specimens with 150

g of solids and a w/b of 0.4 were prepared to study the heat of hydration at 23°C.

Distilled water was added to the solids and mixed for 2 minutes in a steel bowl using a

kitchen hand-blender at low speed. After 2 minutes, approximately 8 g of paste sample

were extracted from the bowl using a 10 ml syringe and injected into a glass ampoule. All

paste samples were weighed by mass difference between the glass ampoule with the

sample and the empty glass ampoule. The sample was then sealed and placed in the

calorimeter, five minutes after the distilled water was initially added. A corresponding

reference sample containing inert silica sand was also placed into the calorimeter. The

amount of silica sand was determined by calculating the equivalent specific heat capacity

to 8 g of PC paste. Heat of hydration for each paste specimen was measured over seven

days and performed in duplicate. The rates of heat evolution (mW/g) were measured and

recorded approximately every 10 seconds using a computer data acquisition system.

Since mixing of the constituents was carried out prior to introducing the sample into the

calorimeter, the first five minutes of heat evolution were not measured.

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3.3.2 Normal Consistency

Normal consistency is a term that is used to describe the degree of plasticity of a freshly

mixed PC paste. The normal consistency (w/b ratio expressed as a percentage) was

determined for all binders in accordance with ASTM C187. For each binder blend, 650 g

of solid material were mixed with water to make a paste. The amount of water required to

bring the paste to a standard condition of wetness was regulated by the condition for

which the penetration of a standard needle (Vicat needle) into the paste is 10 ± 1 mm in

30 seconds. In order to gain appreciation for the accuracy of this test, ASTM C187

stipulates that the results of single-operator tests should not differ by more than 0.7%.

3.3.3 Initial Setting Time

The initial setting time is often used to evaluate if a paste is undergoing normal hydration

reactions. Initial setting time is defined as the time that elapses from the moment water is

added until the paste ceases to be fluid and plastic. Most PCs attain initial set within two

to four hours. For each binder blend, the paste that was mixed to determine normal

consistency was also used to determine initial set time. The time of initial setting of the

blended pastes was determined using a Vicat apparatus according to ASTM C191. The

time at which the needle penetrates 25 mm into the paste at room temperature was taken

to define the initial setting. ASTM C191 specifies that the penetration of the Vicate

needle in the paste should be checked 30 minutes after moulding and every 15 minutes

thereafter until a penetration of 25 mm or less is obtained. According to ASTM C191, the

single operator standard deviation has been found to be ±12 minutes within a range of 49

to 202 minutes initial setting time. To increase the accuracy of the initial set time

measurement, the test procedure was modified by increasing the frequency of the Vicat

penetrations to every five minutes as the paste approached initial set.

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3.3.4 Flow

Flow is used to describe the relative mobility (ability to flow) of mortar. The flow for

each binder blend was determined on a flow table as described in ASTM C230. Mortars

were mixed in accordance with ASTM C305 with one part of binder blend, 2.75 parts of

graded sand, and deionized water. Mortars were mixed for each binder blend to

determine (i) the flow at a fixed w/b ratio of 0.485 and (ii) the water demand to yield a

flow of 110 ± 5 according to ASTM C1437. ASTM C1437 states that the results of

properly conducted tests should differ by no more than 11% for single-operator testing.

3.3.5 Compressive Strength

Compressive strength is the most commonly used method to assess cement quality. The

compressive strength for each binder blend was determined according to ASTM C109

(CSA A456.2-C3) at 1, 3, 7, 28, and 90 days. 50 mm mortar cube specimens were

prepared by mixing one part of binder blend material, 2.75 parts of graded sand, and

deionized water addition (w/b ratio of 0.485). The specimens were cured in a humidity

chamber at 23±1 °C for 24 hours, then demoulded and immersed in lime saturated water

until tested. The compressive strength result is the average of three test specimens from a

single batch at the specified curing time. ASTM C109 states that when three cubes

represent a test age, the maximum permissible range between specimens from the same

mortar batch at the same test age is 8.7% of the average.

3.3.6 Expansion in Limewater

ASTM C1038 is a test method that is used to determine the expansion of mortar bars

made from PC in saturated limewater. The amount of expansion is typically related to the

amount of calcium sulfate in the PC. In this study, ASTM C1038 was used to assess the

expansion of all binder blends. Mortars were mixed in accordance with ASTM C305 with

one part of binder blend, 2.75 parts of graded sand, and deionized water. The amount of

water required to yield a flow of 110 ± 5 according to ASTM C1437 was used for each

binder blend. Four mortar bar specimens (25 x 25 x 285 mm) were prepared for each

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binder blend and the expansion was calculated as the mean of four mortar bars. The test

method specifies calculating the difference in length of specimens at 24 hours from the

time the binder blend was mixed with water and at 14 days. The length change of the

mortars made from different blends, however, was also measured up to one year for most

blends. An expansion limit of 0.020% in 14 days of limewater immersion is in use in

CSA A3001.

3.3.7 Autoclave Expansion

Soundness refers to the ability of a paste to retain its volume after it has set. Unsoundness

can arise from excessive amounts of hard burned free lime or free magnesia and has the

potential to cause delayed destructive expansion. In the autoclave expansion test (ASTM

C151), a cement paste specimen (25 x 25 x 285 mm) is placed in an autoclave for three

hours at 2 MPa and approximately 216°C. The difference between measurements of the

specimen taken before and after the autoclave treatment represents the expansion due to

unsoundness. The autoclave expansion test method was used to measure expansion due to

the combined effects of both magnesia and free lime for each binder blend. For each

binder blend paste, the same w/b ratio used to attain normal consistency and initial setting

time was used for the autoclave test. ASTM C151 states that the results of two properly

conducted tests by the same operator for expansion of similar batches should not differ

from each other by more than 0.07% expansion.

3.3.8 Alkali Silica Reactivity

The concrete prism test is typically used to evaluate the reactivity of aggregate with

respect to ASR and also to examine the impact of materials that may be introduced to

suppress the expansion due to ASR. The typical test period for evaluating the reactivity

of an aggregate is one year, and at least two years with SCM (CSA A23.2-14A and

ASTM C1293). For the proposed research study, this test method was modified to assess

the direct impact on ASR when using CKD as a partial replacement of PC. The main

136

purpose of this study was to make relative comparison of the binary blends rather than

obtaining the absolute values.

The materials used for the ASR concrete durability study were six different CKDs (A, B,

C, D*, E and F) and two PCs of high and low alkali content (TI and TII). CKD D and the

fillers were unfortunately not available at the time of casting for the concrete prisms. Two

series of concrete prisms were cast to assess the effect of CKDs on ASR with Cements TI

and TII. The reactive aggregate susceptible to ASR that was used in this study is Sudbury

aggregate.

The w/b ratio for all mixes was in the range of 0.42 – 0.45 to maintain a constant slump.

The three equal reactive coarse aggregate fractions by mass were of 10, 15, and 20 mm

nominal maximum diameter, respectively. The specific gravity of the reactive coarse

aggregate was 2.71. The fine aggregate had a fineness modulus of 2.90 and a specific

gravity of 2.68. The freshly mixed concrete was tested for slump (ASTM C143), air

content (ASTM C231, pressure method), and unit mass (ASTM C138). Two concrete

cylinders measuring 100 x 200 mm were prepared from each batch. The cylinders were

stored moist at 38 ºC and tested for compressive strength at 28 days. Four concrete

specimens from each batch were prepared, measuring 75 x 75 x 300 mm. The expansion

of the concrete specimens was measured every three months for a period of 365 days.

For each concrete mixture investigated, the expansion (length change divided by the

gauge length) was calculated as the mean of four concrete prisms. Mass was also

measured for each concrete prism and the mass change was averaged for the four prisms.

ASR Test Series 1: The first set of concrete prisms was cast using 10% replacement of

Cement TI with CKD binders (CKD and/or PC). The total alkali content of the concrete

was increased to 1.25% Na2Oe of binder mass by adding sodium hydroxide (NaOH) to

the mixing water. Cement TI as the binder material alone was used in two control

mixtures (Cements TI CTL 1 and CTL 2). The total solid binder was 420 kg/m3 for each

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mix except for Cement TI CTL 2, which was 378 kg/m3. Cement TI CTL 2 contained the

same amount of PC as in the concrete blends with CKDs. Due to the reduction in solid

binder material, the Cement TI CTL 2 alkali level was increased to 1.38% Na2Oe of

binder mass to give the same total alkali loading as the other blends in Test Series 1.

ASR Test Series 2: The second set of concrete prisms was cast using Cement TII and

varying amounts of PC replacement with CKDs. A constant amount of NaOH was added

to each mix. The total alkali content of the concrete was increased to 1.25% (Na2Oe) of

cement mass by adjusting the amount of CKD replacement in each mix. The amount of

NaOH addition to each mix was selected to maintain the range of CKD replacement

levels generally close to 10%. The total solid binder for each mix was 420 kg/m3. Cement

TII as the binder material alone was used in two control mixtures (Cements TII CTL 1

and CTL 2). Cement TII CTL 2 alkali content was raised using NaOH to a level of 1.03%

Na2Oe of binder mass, rather than the 1.25% of alkali loading to give the same total alkali

loading contribution of NaOH as the other CKD blends in Test Series 2.

138

4.0 RESULTS AND DISCUSSION

4.1 Material Characterization

The first objective of this thesis was to characterize the seven CKDs, two PCs, and two

filler materials. It was found that some of the analytical methods designed for PC do not

always provide accurate compositional analysis for CKDs. Therefore, the analytical

methods required for accurate analysis of CKDs were identified. The complete chemical

analysis and physical properties (relative density, Blaine fineness, and percentage of fine

material below 45 µm) of all materials were performed. In addition to the chemical

composition and standard fineness tests, quantitative mineralogical compositions, particle

size distributions, and dilute stirred suspension analyses were also performed.


The characteristics of materials used in cement are traditionally evaluated by an oxide

composition based on chemical analysis data. Chemical makeup of a CKD and PC can

provide an important indicator of how the CKD-PC blend will perform. It was found that

there are very few published works with complete chemical analysis of CKDs in the

research of CKD-PC blends. The incomplete CKD chemical composition data provided

in previous studies is likely due in part to the application of analytical procedures that are

specifically designed for PC, rather than CKDs.

The chemical compositions of the two PCs were determined in accordance with ASTM

C114 using X-ray fluorescence (XRF), as stated in Chapter 3. Prior to XRF analysis, loss

on ignition (LOI) was performed by igniting the 110˚C dried sample to a constant mass in

a muffle furnace at 950 ± 50˚C in an uncovered crucible for 1h. The LOI values obtained

result from either exposure to moisture or CO2 (since each of the two PCs only consists

of clinker and gypsum, there is no contribution of CO2 from carbonate additions).

139

CKDs usually take between 12 to 24 hours to reach constant mass at 950 ± 50 ˚C. The

LOI for CKDs not only reflects prehydration and decarbonization, but also the presence

of volatiles (alkali, sulfate, and/or chloride). The ranges of volatilization at the melting

point of compounds found in CKDs are shown in Table 4.1. A large percentage of the

CKD volatiles will be released from the sample into the atmosphere during the LOI test

and during preparation of the fused beads since they are less stable in CKDs than in PC at

950 ± 50 ˚C. This presents two problems: (i) the LOI is not just CO2 and (ii) the XRF

quantification of alkali, sulfate, and/or chloride is underestimated. Therefore, direct

testing procedures developed for PC in ASTM C114 were used to accurately determine

the volatile composition of the CKDs (Babikan and Verville, 2007). The test methods

used to measure the volatiles of CKDs were: flame photometry for alkalis, induction

heating for sulfate, and potentiometric titration for chloride. The XRF chemical analysis

values were then corrected by accounting for the volatiles that were released during the

LOI test. The process that was used for chemical analysis of the CKDs is described in

Figure 4.1. The CKD chemical composition calculations are presented in Appendix A.

Table 4.1 Melting points and volatility of compounds in CKDs (Manias, 2004)

(Note: This table is the same as Table 2.3)

Volatile Compounds Melting Point, ˚C Range of volatility*, %

CaCl2 772 60 to 80

KCl 776 60 to 80

NaCl 801 50 to 60

Na2SO4 884 35 to 50

K2SO4 1069 40 to 60

CaSO4 1280 ---

*Range of volatility: % of compound that will volatilize at melting point

140

Figure 4.1 Process flow chart for CKD chemical composition analysis

The free lime test for PCs is typically used to determine the free calcium oxide content.

This test, however, is also sensitive to calcium hydroxide. The free lime test gives the

total of free calcium oxide plus calcium hydroxide contents and does not differentiate

between the two. This is generally not an issue for PC free lime analysis since the

presence of calcium hydroxide is rare (except in PC that consists of weathered clinker).

CKDs, however, can be exposed to moisture during processing to reduce fugitive dust

and/or storage outside. Therefore, the results from the free lime test for CKDs should be

considered as representative of the combined free calcium oxide and calcium hydroxide

contents.

CKD Sample

CKD Sub-sample 1

CKD Sub-sample 2

CKD Sub-sample 3

CKD Sub-sample 4

LOI and XRF

Analysis

Calculate chemical composition by

accounting for volatiles

released during LOI test

Chloride Content: Potentiometric

Titration

Sulfate Content: Induction Furnace

Alkali Content:

Flame Photometry

141

The chemical and standard physical properties (relative density, Blaine fineness, and fine

material below 45 µm) of all materials are shown in Table 4.2. Cement TI met the

specifications for normal PC and is characterized by a relatively high sulfate (4.35%),

high total alkali content (0.97%), and high C3A content (11.3%). Cement TII met the

specification for a moderate sulfate resistant cement and is characterized by its low C3A

(6.1%) and low total alkali (0.57%) contents. The data in Table 4.2 shows the LS and

SLX to consist of 95.52% calcite based on 53.49% / 56.00% CaO (by LOI, 42.29% /

44.00% = 96.11%) and 98.15% quartz, respectively.

Comparison of the current CKDs to those from previous research studies as summarized

by Sreekrishnavilasm et al. (2006) (Table 2.5) shows that all CKDs were within the

maximum-minimum range of the compositions, except for the free lime values for CKDs

E and F. CKDs A, B, and C appear to be particularly similar to those in the previously

published literature. CKDs A and C were within the standard deviations for each

parameter. CKD B had concentrations of calcium oxide, silicon dioxide, and aluminum

oxide slightly outside the respective range for standard deviation. CKDs D*, D, E, and F,

however, appear to be slightly different from the published dataset. CKDs D*, D, and E

each had values for sulfate above the range for standard deviation. CKDs D*, E, and F

had higher free limes than the upper limit of the standard deviation. CKDs E and F also

had calcium oxide and magnesium oxide contents above the respective ranges for

standard deviation. The chloride levels of the CKDs within this study appear to be lower

than the full range of chloride levels found in CKDs from previous studies.

As a note of interest, the CKD oxide composition statistical analysis of intermittent daily

samples collected over a 3 year period from the same kiln source as CKD C is presented

in Table 2.9. Although more variable than PC, the standard deviation results indicate that

the CKD from this kiln source is quite consistent.

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Table 4.2 Chemical and select physical components of PC, CKD, and filler materials

(mass %)

PCs Cement Kiln Dusts (CKDs) Fillers

Wet Long-dry PH/PC

Components TI TII A B C D* D E F LS SLX

CaO 62.03 63.06 44.32 32.70 44.75 51.12 45.51 55.18 55.86 53.49 0.02

SiO2 19.15 20.39 14.25 24.07 14.30 14.23 14.41 15.25 16.81 2.60 98.15

Al2O3 5.83 4.21 3.77 9.12 4.02 4.05 4.93 3.78 3.94 0.68 0.47

Fe2O3 2.46 3.01 1.92 3.78 1.60 2.05 2.16 2.26 1.94 0.21 0.06

MgO 2.18 3.21 1.80 1.82 1.02 2.00 1.68 2.85 3.08 0.55 0.00

SO3 4.35 2.98 3.03 5.79 7.30 15.05 16.15 11.75 8.97 0.03 0.03

Na2O 0.30 0.13 0.60 0.53 0.19 0.40 0.66 0.26 0.32 0.02 0.01

K2O 1.01 0.69 3.35 4.81 3.20 3.32 4.47 4.83 3.66 0.21 0.08

Na2Oea 0.97 0.58 2.80 3.69 2.30 2.58 3.60 3.43 2.73 0.16 0.06

Na2O soluble 0.16 0.06 0.38 0.30 0.10 0.21 0.39 0.17 0.14 0.00 0.00

K2O soluble 0.97 0.64 2.66 3.88 1.97 2.13 2.9 3.94 2.42 0.00 0.00

Na2Oeb soluble 0.80 0.49 2.13 2.85 1.40 1.61 2.30 2.76 1.73 0.00 0.00

Na2Oeb / Na2Oe

a 0.82 0.84 0.76 0.77 0.61 0.62 0.64 0.80 0.64 0.00 0.00

Ti2O 0.25 0.26 0.40 0.55 0.21 0.24 0.26 0.24 0.19 0.03 0.03

P2O5 0.26 0.12 0.12 0.11 0.04 0.12 0.15 0.11 0.09 0.01 0.01

Mn2O 0.09 0.56 0.06 0.06 0.05 0.11 0.08 0.50 0.06 0.01 0.00

Cl- 0.00 0.00 2.49 0.94 0.38 0.22 0.35 2.18 0.85 0.00 0.00

LOIc 1.79 1.28 28.74 17.85 23.76 8.23 9.96 5.88 5.47 42.29 0.20

Total Sum (High)d 99.92 99.88 104.95 102.15 100.84 101.16 100.83 105.07 101.27 100.15 99.06

Total Sum (Real)e 99.92 99.88 99.08 99.79 99.73 100.31 100.02 99.74 99.34 100.15 99.06

Free Limef 0.70 1.53 4.50 4.04 5.70 18.20 10.59 29.20 38.20 0.00 0.00 a Equivalent Alkali (Na2O + 0.658 K2O) b Equivalent Water Sol. Alkali (Water Sol. Na2O + 0.658 Water Sol. K2O) c Loss on ignition determined at 950 ± 50 ºC d XRF sum of total oxides e Sum of total oxides calculated by removing the volatiles that are included in the LOI (Na2O, K2O, Cl-) f Free lime: combined CaO & Ca(OH)2 content

Each CKD has its own characteristics, but there can be some generalization of these

particular CKDs based upon the pyroprocess, especially in free lime and chloride

contents. As expected, the wet and long-dry kilns had free lime contents that are lower

than the precalciner kilns. CKDs D* and D have higher free limes than typical long-dry

kiln CKDs due to unique equipment design in the kiln, but they are still lower than the

precalciner CKDs E and F free limes. The long-dry kiln CKDs have low chloride and

high sulfate contents in comparison to the wet and precalciner CKDs.

143

The CKDs were generally higher in total alkali, sulfate, chloride, LOI, and free lime than

Cements TI and TII, as shown in Table 4.1. Water soluble alkalis are not normally

reported for PCs, although the test method is described in ASTM C114. The CKDs

contained higher levels of water soluble alkalis than the Cements TI and TII. It is

interesting to note that although the quantity of soluble alkalis is higher in CKDs, the

ratio of water soluble alkalis to total alkalis is higher in Cements TI and TII.

Statements/Observations:

4.i The ASTM C114 techniques specified for PC chemical analysis are not

necessarily sufficient and/or appropriate for CKD chemical analysis. The mass

of CKD at 950 ± 50 ˚C is not stable until 12 – 24 hours. Therefore, the 1-hour

PC standard LOI test duration is not sufficient to determine LOI for CKDs.

Further, LOI and fused bead preparation of CKDs can cause the volatile

compounds to be released into the atmosphere prior to chemical composition

analysis. Babikan and Verville (2007) recommend using the following tests in

ASTM C114 to determine the chemical composition of CKD volatile

elements:

i. Alkalis: flame photometry

ii. Sulfates: induction furnace

iii. Chloride: potentiometric titration

4.ii Although PC typically only contains free calcium oxide, the PC free lime test

is representative of both free calcium oxide and calcium hydroxide. CKDs are

more likely to contain calcium hydroxide than PC due to exposure to moisture

during handling and storage.

144


CKD mineralogical analysis (determination of the relative abundance of the different

phases) is an essential complement of the chemical analysis. The effects of CKD

elements in a CKD-PC blend may vary depending on the form in which they actually

exist. The characteristics of CKD are traditionally evaluated based on chemical analysis

data. Such data does not, however, indicate the ways in which the different elements

actually exist within the CKD and how they might be expected to react during hydration.

Soluble alkalis, for example, may occur as separate crystalline phases in the form of

alkali chlorides or alkali sulfates. The reactivity of elements may, therefore, be expected

to vary, depending on the form in which they actually exist.

The traditional methods (Bogue equations, XRD Rietveld analysis, and thermal analysis)

were used to assess the PC mineralogical compositions. Although quantifying the

mineralogical composition of PC has been thoroughly explored, the data to quantify the

mineralogical phases of CKDs is relatively limited. Mineralogical analysis of CKDs has

not been thoroughly evaluated due to a lack of quantitative analytical techniques. A

method for mineralogical phase quantification of CKDs using XRD diffraction scans,

Rietveld refinement, and physical tests (thermal analysis and titration) is introduced in

this section.

145

Rietveld analyses of Cements TI and TII were performed using the X-ray diffraction

scans and control files developed “in-house” at Lafarge North America. The

mineralogical compositions of the PCs were determined by Rietveld quantitative X-ray

diffraction analysis, shown in Table 4.3(a). Alite (impure C3S) typically contains 3 – 4%

of substituent oxides, the most significant of which are iron, magnesium, and aluminum.

Belite (impure C2S) may contain 4 – 6% of substituent oxides of which aluminum and

iron are most common (Taylor, 1997). The potential proportions of C3S, C2S, C3A, and

C4AF compounds in each PC, calculated based on the Bogue equations in ASTM C150,

are shown in Table 4.3b. Taylor (1997) has noted that Bogue calculations can differ

considerably from the true phase compositions, especially by underestimation of alite and

overestimation of belite because the actual composition of these phases differs

considerably from those of the pure form.

Table 4.3 Cements TI and TII mineralogical composition (mass %) (a) XRD Rietveld Analysis (b) Bogue Compound Calculation

Phase TI TII Phase TI TII

Alite, C3S 68.6 66.5 C3S 51.9 60.7

Belite, C2S 10.3 15.2 C2S 15.8 12.6

Aluminate, C3A 8.7 3.0 C3A 11.3 6.1

Ferrite, C4AF 7.5 8.9 C4AF 7.5 9.1

Lime, CaO 0.0 0.2

Periclase, MgO 1.4 2.5 Gypsum, CaSO4·2H2O 1.7 1.0

Hemihydrate, CaSO4·0.5H2O 0.5 0.6

Anhydrite, CaSO4 0.2 0.9

Calcite, CaCO3 0.7 0.8

Portlandite, Ca(OH)2 0.1 0.4

Quartz, SiO2 0.3 0.2

146

Cement TI has considerably more gypsum (readily soluble calcium sulfate) than Cement

TII. PC with high aluminate contents typically require a sufficient amount of added

calcium sulfate as a set controlling agent, which increases the sulfate content of the PC. It

follows that cements low in aluminate require less added calcium sulfate and would tend

to have lower sulfate contents.

Thermogravimetric analysis (TGA) is ideally suited to quantify the degree of calcination

and amount of calcium hydroxide (portlandite) present in CKDs. Samples were tested in

a temperature range from 30˚C to 950˚C. Portlandite decomposed between 400 to 530˚C

and calcium carbonate was detected between 700 to 850˚C. The TGA results for Cements

TI and TII and the CKDs are presented in Appendix B. An approximate determination of

portlandite (Ca(OH)2) was established using mass balance calculations and the TGA

results. The portlandite was then subtracted from the total free lime (calcium oxide and

calcium hydroxide) in Table 4.2 (based on equivalent calcium oxide) to determine the

free calcium oxide (CaO) portion. The mineralogical composition of calcite, portlandite,

and free calcium oxide is shown in Table 4.4.

Table 4.4 CKD mineralogical compositions using direct test methods (mass %)

Components Cement Kiln Dusts (CKDs) A B C D* D E F

CaCO3 52.6 34.7 51.3 17.3 22.7 1.8 6.5 free CaO 4.5 4.0 5.7 18.2 10.6 28.4 34.5 Ca(OH)2 0.0 0.0 0.0 0.0 0.0 1.0 4.9

147

Rietveld XRD analysis was used to accurately estimate the overall mineralogical phases

quantification of each CKD. The CKD crystal phases were identified using XRD scans

and Joint Committee on Powder Diffraction Standards (JCPDS) files. CKDs typically

contain some phases that cannot be observed by XRD. Clay minerals, glass, and similar

poorly crystalline components fall into this class and are called amorphous (without form

or crystal structure). Different types of amorphous materials, however, may provide an

indication of their presence as broad patterns or “humps”. X-ray powder diffraction is

only sensitive to crystalline materials.

During normal Rietveld analysis, the amorphous component of a sample is not

considered and the relative mass fractions of the crystalline phases are normalized to

100%. This was corrected using a known amount of either calcite or free lime determined

by TGA, as shown in Table 4.4. In deciding which phase quantity to use, the best fit

results were achieved using the most abundant phase for each respective CKD Rietveld

Refinement. Therefore, CKDs A, B, C, and D were quantified relative to their calcite

value, and CKDs D*, E and F were quantified relative to their free calcium oxide content.

Adding the known mass of the phase to the Rietveld analysis allowed the amorphous

phase to be incorporated in the analysis. Furthermore, absolute mass fractions were

obtained for all phases. The results of the quantitative phase analyses using TGA, XRD,

and Rietveld are shown in Table 4.5. The XRD scans are presented in Appendix C.

Calcite was identified as the major phase for CKDs A (52.6%), B (34.7%), C (51.3%),

and D (22.7%), which are from the wet and long-dry processes. Free lime is the dominant

phase in CKDs D* (18.2%), E (28.4%), and F (34.5%). CKDs E and F are from

precalciners, while CKDs D and D* have uncharacteristically high free limes for a long-

dry kiln process. Quartz was present in all CKDs in a range from 3 – 11%. Periclase was

present at approximately 2% for CKDs E and F, but less than 1% for the other CKDs.

CKDs A and B contained minor amounts (≤5%) of dolomite. CKDs E and F had minor

amounts of portlandite, while CKD B had only trace amounts. CKDs E and F are from

148

precalciner kilns that are equipped with water conditioning towers to reduce CKD

fugitive dust. The water from the conditioning tower converts a portion of the free lime to

calcium hydroxide.

Table 4.5 Mineralogical composition of CKD and filler materials (mass %)

Cement Kiln Dust

Wet Long-dry PH/PC

Category Phase CKD A CKD B CKD C CKD D* CKD D CKD E CKD F

Calcite, CaCO3 52.6 34.7 51.3 15 22.7 1 4

Quartz, SiO2 9 7 11 4 3 7 6

Dolomite, CaMgCO3 5 3 - - 1 - - Raw Feed

Periclase, MgO <1 <1 <1 <1 <1 2 2

Alite, C3S 1 - 1 6 2 2 <1

ß-Belite, C2S 22 8 11 7 6 14 4

Aluminate, C3A <1 <1 <1 <1 <1 1 <1

Clinker Phases

Ferrite, C4AF <1 <1 <1 <1 - 2 <1

Lime, CaO 4 3 5 18.2 12 28.4 34.5 Free Lime Portlandite, Ca(OH)2 - <1 - - - 1 3

Anhydrite, CaSO4 2 2 5 12 18 14 6 Calcium Langbeinite,

2CaSO4.K2SO4 - - 2 4 3 1 1 Aphthitalite, K3Na(SO4)2 - <1 - - 2 - -

Arcanite, K2SO4 - 2 <1 - - <1 <1

Sulfates

Calcium Sulfoaluminate,

(AFt, AFm) - - 1 1 <1 1 <1

Chlorides Sylvite, KCl 3 1 <1 - <1 4 <1

Calcium Chloride,

CaCl2 - - <1 - - - -

Amorphous <1 32 11 31 29 18 35 Akermanite,

Ca2Mg(Si2O7) - - - - - 1 - Calcium

Dialuminum Oxide, CaAl2O4 - - - - <1 1 1

Clays, Raw

Materials (slag, fly ash), &

Intermediate Phases

Mullite, Al6Si2O13 - 4 - - - - -

Note: All values are from XRD analysis except those that are in bold

149

Each CKD consisted of some or all of the four major PC phases. The total sum of cement

phases in the CKDs ranged between 4% (CKD F) and 25% (CKD A). Belite was the

most prevalent PC phase in each CKD within a range of 4% and 22%. Each CKD

contained alite in a range between <1% and 2%, with the exception of the

uncharacteristic CKD D* which had 6%. All of the CKDs except CKD E had aluminate

and ferrite each with <1%. CKD E had higher amounts of aluminate (1%) and ferrite

(2%).

Anhydrite was present in all CKDs, with the highest amounts in CKDs D* (12%), D

(18%), and E (14%). Alkali sulfate salts were present in all seven CKDs. Calcium

langbeinite was found in all CKDs except CKDs A and B, in a range of 1% and 4%.

CKDs B, C, E, and F each contained arcanite in a range of <1 – 2%. Aphtithalite was

identified in CKDs B (<1%) and D (2%). Calcium sulfoaluminate, which reacts readily

with water, was present in small amounts (<1 – 2%) in all CKDs, except CKDs A and B.

CKDs A and E contained sylvite ≥3%, while CKD B contained 1%. Small amounts of

sylvite (<1%) were present in CKDs C, D, and F, while no traces of sylvite were found in

CKD D*. CKD C was the only sample found to contain calcium chloride (<1%).

Amorphous material is mostly a reflection of clay minerals, partially dehydrated clay

minerals, and/or supplementary raw materials such as fly ash or slag. CKDs B, D*, D,

and F had amorphous contents within a range of 29% and 35%. CKD E contained 18%

and CKD C had 11% amorphous content. CKD A had very little amorphous material

(<1%). Small amounts of calcium dialuminum oxide were found in CKDs D, E, and F

(≤1%). CKD E contained akermanite (1%) and CKD B contained mullite (4%).

Akermanite, calcium dialuminum oxide, and mullite are phases typically found in

alumina supplementary raw material sources. Akermanite is typically found in slag and

mullite is typically found in fly ash.

150

X-ray diffraction techniques were developed to determine the composition of the CKDs.

The composition and quantity of the crystalline and amorphous phases of the seven

CKDs differed significantly. The type of crystalline material and the relative proportion

of the amorphous and crystalline material in CKDs can significantly affect the hydration

of a CKD-PC blend. Also, previous literature studies have not identified significant

amounts of calcium langbeinite in CKDs. Tang and Gartner (1988) have reported on the

effects of calcium langbeinite on PC hydration. They concluded that calcium langbeinite

is a more effective retarder of C3A than either gypsum or pure alkali sulfates alone. The

proposed mechanism takes into account the rate at which the sulfate phases can supply

both calcium and sulfate ions to the surfaces of the aluminate phases during early stage

hydration. The presence of calcium langbeinite increases the rate and chemical potential

at which calcium sulfate enters into solution. Finally, although not previously reported, it

appears CKDs can contain fly ash and/or slag if these materials are used as raw meal in

clinker production. CKD B contains mullite (typically found in fly ash) and CKD E

contains akermanite (typically found in slag).


4.iii Fresh CKDs from precalciners may contain portlandite due to the combination

of high free lime and the use of water sprays used to condense materials in the

preheater gas stream. TGA can be used to determine the CKD calcium

hydroxide content.

4.iv Preheater/precalciner CKDs have very high free limes (28 – 35%) compared

to CKDs from wet (3 – 4%) or long-dry (5 – 18%) processes.

4.v XRD and Rietveld refinement, combined with TGA and the free lime test, can

be used to quantify the actual CKD crystalline composition and amorphous

content.

151

4.vi The amorphous and/or clinker phase contents in CKDs can be as high as

approximately 23% and 35%, respectively.

4.vii CKDs can contain calcium langbeinite (up to approximately 4%). Calcium

langbeinite is readily soluble and can provide excess sulfate to the system

causing early precipitates to form, such as syngenite and secondary gypsum.

This can lead to observable changes in workability.

4.viii Fly ash and/or slag may also be present at low levels (1 – 4%) if used as raw

materials in clinker production. CKD B contains mullite (typically found in

fly ash) and CKD E contains akermanite (typically found in slag).


Important physical properties required to understand the behaviour of binder blends using

CKD, PC and fillers are relative density, fineness, and particle size distribution. The

relative density, Blaine air-permeability (ASTM C204), and the percent passing a 45 µm

sieve are traditional methods that were used to characterize the fineness of all materials in

this research program; they are shown in Table 4.6. The usual procedures used to

measure PC fineness were slightly modified to accurately measure the fineness of the

CKDs and fillers. These modifications are described in this section. The particle size

distribution (PSD) analysis is more recently developed technology that was also used.

The PSD results are presented in Figure 4.2 and Figure 4.3. The mean particle size or D50

(the equivalent diameter where 50% by volume of the particles has a smaller diameter

and hence the remaining 50% is coarser) and D10 (the equivalent diameter where 10% by

volume of the particles has a smaller diameter and hence the remaining 90% is coarser)

for all materials are also presented in Table 4.6.

152

Table 4.6 Physical properties of all materials

PCs Cement Kiln Dusts (CKDs) Fillers

Wet Long-dry PH/PC

Properties TI TII A B C D* D E F LS SLX

Relative Density 3.11 3.18 2.75 2.65 2.77 2.89 2.86 2.97 2.82 2.71 2.66

Blaine (m2/kg) 367 377 654 684 681 177 610 350 526 488 638

45µm (% passing)a 95.74 92.01 73.30 63.10 71.10 56.90 87.23 69.00 74.90 99.54 98.09

D50 (µm) 15.51 14.37 14.09 18.31 13.73 36.98 9.71 22.58 15.99 9.22 11.42

D10 (µm) 3.40 2.98 2.25 2.19 1.91 8.62 2.13 4.39 2.35 1.57 1.36 a Fineness: determined as material finer than 45µm mesh sieve

The relative densities of Cements TI (3.11) and TII (3.18) are fairly close to the generally

accepted average value of 3.15 for PCs in ASTM. The relative densities of the CKDs

range between 2.65 and 2.97, which is lower than PC. As a result, if CKD is used as a

partial replacement of PC by mass, a larger volume of CKD particles will replace the PC

particles removed (assuming the CKD particles are equivalent in size to the PC particles)

and the volume of paste will increase. The filler relative densities were in the lower range

of the CKD relative densities.

In order to attain accurate Blaine fineness results, the measured density for all CKDs and

fillers was used for the Blaine analysis calculations, rather than the standard 3.15

specified in ASTM for PCs. Also, although PCs typically do not require it, ultrasound

treatment was used for all materials during particle size laser diffraction. Since particle

size laser diffraction is not able to differentiate between individual particles and

agglomerated particles, some fine powders used in the cement industry that have a higher

tendency for agglomeration, such as silica fume, require ultrasound treatment. CKDs can

have very fine particles that agglomerate affecting the accuracy and precision of the PSD

analysis.

153

Cements TI and TII have similar Blaine fineness values to other commercially available

PCs given by Tennis and Bhatty (2006). The Blaine fineness values for CKDs A (654

m2/kg), B (684 m2/kg), C (681 m2/kg), and D (610 m2/kg) are similar, while Blaine

fineness values for CKDs E (350 m2/kg) and F (488 m2/kg) are lower. CKDs E and F

come from preheater/precalciner kiln systems, which are reported to generate coarser

CKD than wet and long-dry processes. CKD D* has an uncharacteristically low Blaine

fineness (185 m2/kg) for a long-dry kiln and is not considered typical. All CKDs had

higher Blaine fineness values than Cements TI and TII except CKDs D* and E. The

percentage of materials passing 45 µm sieve for the TI and TII were 95.74% and 92.01%,

respectively. Each CKD had considerably lower percentage of material passing the 45

µm sieve, with the range being between 56.90% and 87.23%. The CKDs may have a

broader particle size range than found in the PCs since the CKDs are not selected based

upon size through a separator. The percentage passing 45 µm sieve for LS (99.54%) and

SLX (98.09%) are slightly higher than for the PCs.

The full range of particle size distribution for all materials is shown in Figure 4.2.

Cements TI and TII have very similar particle size distributions. The overall trend

indicates the CKDs generally straddle both sides of the PCs. The black arrow indicates

that in the area of larger particles (between 10 µm and 100 µm), CKDs A, B, C, D*, E,

and F, are coarser than the PCs. Both fillers appear to be finer than the PCs. Figure 4.3 is

a plot of the particle size distributions up to 10 µm (finer particles). CKDs A, B, C, D,

and F appear to have more fine particles than PC or fillers.

154

The Blaine fineness values reflect that the CKDs are generally finer than the PCs, but the

percentage passing 45 µm sieve values indicate that the CKDs are coarser than the PCs.

The PSDs help to explain the reasons for the conflicting results. The correlation

coefficient (r) indicates the strength and direction of a linear relationship between two

random variables. The first two random variables are Blaine fineness and PSD, shown in

Figure 4.4(a). The second two random variables are percentage passing 45 µm sieve and

PSD, shown in Figure 4.4(b). The Blaine fineness value is strongly correlated to the

particle size distribution below 10 µm, particularly 3 µm. Therefore, it can be concluded

that the CKDs generally have more fine particles (<10 µm) than PCs. Since the Blaine

fineness does not correlate well to the particles above 10 µm (r < 0.7), the Blaine fineness

indicates very little about the material PSD overall. The percentage of material passing

the 45 µm sieve has a good correlation (r > 0.7) to the particle size from approximately

10 µm to approximately 100 µm. Therefore, the Blaine fineness is representative of the <

10 µm portion of the PSD and the percentage passing 45 µm sieve is representative of the

> 10 µm portion of the PSD.

155

Figure 4.2 Particle size distribution of PC, CKD and filler. The materials are in the

direction and position of the arrow: LS, D, SLX, TII, TI, A, F, C, E, B, D*

Figure 4.3 Particle size distribution of PC, CKD and filler between 0.1 µm and 10 µm.

The materials are in the direction of the arrow: LS, SLX, C, D, B, A, F, TII, TI, E, D*

156

(a)

(b)

Figure 4.4 CKD fineness correlation between (a) Blaine fineness and particle size

distribution, and (b) percentage passing 45µm sieve and particle size distribution

R elations hip between B laine and

P S D for C K D s

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

0.1 1 10 100 1000

P a rtic le siz e (µm)

Co

rre

lati

on

Co

eff

icie

nt

(r)

R elations hip between P erc entag e P as s ing 45 µm

S ieve and P S D for C K D s

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

0.1 1 10 100 1000

P a rtic le siz e (µm )

Co

rre

lati

on

Co

eff

icie

nt

(r)

157


4.ix There are two ways to modify the current PC analysis methods for accurate

Blaine fineness and PSD CKD analyses:

i. The relative density of the CKD should be used in determining the Blaine

fineness value, as opposed to the relative density of PC (3.15), which is

used to determine the Blaine fineness of PCs according to ASTM C114,

and

ii. The PSD of CKDs should include ultrasound treatment to ensure

agglomeration of fine particles does not occur.

4.x CKDs generally have higher Blaine values than PCs. The Blaine fineness test

correlates well with the particle size distribution below 10 µm (r > 0.7),

particularly 3 µm.

4.xi CKDs have a lower percentage of material passing a 45 µm sieve in

comparison to PCs. The CKD percentage of material passing the 45 µm sieve

has a good correlation (r > 0.7) to the CKD particle size from approximately

10 µm to 100 µm.

4.xii CKDs have lower relative density (2.65 – 2.97) than that of Cement TI (3.11)

and Cement TII (3.18).

4.xiii The CKD mean particle sizes (D50) had a range between 9.71 – 22.58 µm.

Cement TI (15.51 µm) and Cement TII (14.37 µm) were within this range.

158

4.1.4 CKD Dissolution Analysis

The dissolution of ionic species in water and composition of the liquid phase play an

important role in PC hydration. The principal ions dissolved in solution are K+, Na+,

Ca2+, SO42-, and OH-. Silicate and aluminate species dissolve to a much lesser extent.

There is a charge balance between the cations and anions in solution. The ion

contributions from CKDs may influence the charge balance and ultimately the solubility

behaviour of phases during the early stages of PC hydration. The liquid phase

composition of a high-alkali PC paste (w/b of 0.5) during hydration over a period of three

months is shown in Figure 4.5.

Figure 4.5 Composition of pore solution w/b 0.5 high alkali PC paste (Gartner et al.,

2002)

159

Rapid ion dissolution at high water/solid ratios gives an indication of the relative

differences between PCs and CKDs. In order to gain appreciation for the ion

contributions from CKDs relative to PC, the liquid filtrate ion compositions of CKDs and

Cements TI and TII at 10:1 water to solid ratio (by mass) in solution after 10 minutes of

mixing were conducted; results are shown in Table 4.7. The total ion contribution from

the CKDs ranges from 3779 to 6735 mg/L, which is significantly higher than the total ion

contributions from Cement TI (1717 mg/L) and Cement TII (1750 mg/L).

Table 4.7 Ionic concentrations of 10:1 water to solid ratio (by mass)

solution analysis @ 10 minutes (concentration mg/L)

TI TII CKD A

CKD B

CKD C

CKD D*

CKD D

CKD E

CKD F

Calcium 731 1095 1338 1426 1570 2368 1789 1873 1730 Chloride 0.00 0.00 1003 1402 497 151 301 2150 832

Potassium 782 517 1730 2260 1502 1550 1910 2464 1639 Sodium 104 38 234 197 62 111 213 97 68

Sulfur 63 48 29 122 73 139 120 71 98

Silica 6.39 3.03 1.32 2.11 3.35 1.25 2.80 1.43 1.35 Alumina 0.57 0.67 0.74 1.50 2.37 0.77 1.81 0.97 0.82

Iron 0.34 0.48 0.48 0.88 1.29 0.29 0.68 0.35 0.23 Magnesium 0.27 0.58 0.41 0.72 1.62 0.38 0.63 0.39 0.69

Hydroxyl Ions 29 47 61 62 66 83 77 77 75

Total Ions 1717 1750 4398 5474 3779 4405 4416 6735 4445

pH* 12.5 12.7 12.8 12.8 12.8 12.9 12.9 12.9 12.9

CKD LEGEND

Bold: Greater than in both PCs

Italics: Greater than in one of the PCs

Regular: Less than or equal to both PCs * pH was calculated using hydroxyl ion concentration in the formula’s; pOH = - log ( OH-) & pH = 14- pOH

160

Calcium, chloride, potassium, alumina, and hydroxyl ions were all significantly higher in

the liquid filtrate of the CKDs in comparison to the concentrations found in the liquid

filtrate of Cements TI and TII. The pH of the CKD liquid filtrates was also higher than

that of the control cements. Sulfur ions were higher in the liquid filtrate of the CKDs than

that of Cements TI and TII, with the exception of CKD A. This is not surprising since the

sulfur content of CKD A was also determined to be lower than that of Cements TI and

TII. Sodium, iron, and magnesium ion contribution levels from CKDs varied in

comparison to the control cements. Silica ion levels of the liquid filtrates for the CKDs

were all lower than the silica ion levels found in the PC liquid filtrates. The lower silica

ion contributions from CKDs are likely due to the lower levels of alite and belite, in

comparison to PCs.

The dilute stirred suspension test results show that the ions available from CKDs during

early stages of hydration will likely be qualitatively the same as the ions available from

PCs, with the exception of chloride ions. Chloride ions, however, are commonly used as

accelerators in concrete mixtures. It is likely that CKD-PC blends will have significantly

higher amounts of ions entering solution during the early stages of hydration, in

comparison to PC alone. The elevated amount of alumina ions in the CKD liquid filtrates

is somewhat surprising since the chemical composition analyses show that most of the

CKDs have lower alumina oxide contents than that found in the PCs. This is an indication

that the alumina in CKDs may be more readily soluble than the alumina in PCs.

161


4.xiv The ion contributions from CKDs are qualitatively the same as the ion

contributions from PC, with the exception of chloride ions.

4.xv Calcium, chloride, potassium, alumina, and hydroxyl ions were all higher in

the CKD liquid filtrates in comparison to the concentrations found in the PC

liquid filtrates at 10 minutes. Although the effects of these ions are not

uniform, these ions can significantly impact the early stages of hydration.

4.xvi The total ion contribution in liquid filtrate of dilute stirred suspensions is

higher from CKDs than PCs at 10 minutes.

4.xvii The pH of the CKD liquid filtrates is higher than that of the PC liquid filtrates

at 10 minutes.

162

4.2 CKD-PC Blends

The second objective of this research program was to develop an improved understanding

of the effects of utilizing CKDs as partial replacements of PC. Although the single effect

of any one of the common components found in CKDs can be stated in general terms,

specific reactions among the multiple components within CKDs are difficult to

contemplate. Since CKDs contain multiple components that affect the properties of

blends, it is difficult to separate the effects of the individual components. Further, the

influence of the same CKD at equal replacement levels of two different PCs can

influence the hydration differently. Therefore, regression analysis was applied where

possible to deduce the relationships between CKD-PC binder properties and various

independent variables.

The combined compositions for the CKD-PC blends were calculated based upon

percentage composition, by mass. All paste and mortar blends were made with 10% and

20% of CKD or filler replacements by total mass of each of Cements TI and TII. The

calculated chemical, physical, and mineralogical properties of these blends are shown in

Appendix D. Overall, 34 different mixtures were prepared using 0% (control), 10%, and

20% of the seven CKDs and two filler replacements by total mass of Cements TI and TII.

As an indication of the composition differences of CKD-PC and PC-filler blends in

comparison to PC alone, the range for the chemical and select physical properties of

CKD and fillers at 10% and 20% replacement of Cements TI and TII are shown in Tables

4.8 (Cement TI blends) and 4.9 (Cement TII blends). The CKD-PC blend chemical and

physical properties that are significantly different from PC alone are in bold and

highlighted.

163

Table 4.8 Range for chemical and physical properties of Cement TI blends at 10% and

20% replacement (Theoretical calculation, mass %)

Components TI CKDs at 10%

TI replacement CKDs at 20%

TI replacement Fillers at 10% TI replacement

Fillers at 20% TI replacement

Min. Max. Min. Max. Min. Max. Min. Max.

SiO2 19.15 18.66 19.65 18.17 20.14 17.50 27.05 15.84 34.95

Al2O3 5.83 5.62 6.16 5.42 6.49 5.29 5.32 4.76 4.80

Fe2O3 2.46 2.37 2.59 2.28 2.72 2.22 2.23 1.98 2.01

CaO 62.03 59.10 61.41 56.16 60.80 55.83 61.18 49.63 60.32

MgO 2.18 2.07 2.27 1.95 2.36 1.96 2.02 1.75 1.86

SO3 4.35 4.22 5.53 4.09 6.71 3.92 3.92 3.49 3.49

Na2O 0.30 0.29 0.34 0.28 0.37 0.27 0.27 0.24 0.24

K2O 1.01 1.23 1.39 1.45 1.78 0.92 0.93 0.83 0.85

Na2Oe 0.97 1.10 1.24 1.23 1.51 0.88 0.89 0.79 0.80

Sol. Na2O 0.16 0.15 0.18 0.15 0.21 0.14 0.14 0.13 0.13

Sol. K2O 0.97 1.07 1.26 1.17 1.56 0.87 0.87 0.77 0.77

Sol. Na2Oe 0.80 0.86 1.00 0.92 1.21 0.72 0.72 0.64 0.64

TiO2 0.25 0.24 0.28 0.24 0.31 0.23 0.23 0.21 0.21

P2O5 0.26 0.24 0.25 0.21 0.24 0.23 0.23 0.21 0.21

Mn2O3 0.09 0.08 0.13 0.08 0.17 0.08 0.08 0.07 0.07

Cl 0.00 0.03 0.25 0.07 0.50 0.00 0.00 0.00 0.00

Ca(OH)2 0.40 0.36 0.85 0.32 1.30 0.36 0.36 0.32 0.32

fCaO 0.40 0.76 3.81 1.13 7.22 0.36 0.36 0.32 0.32

LOI 1.79 2.15 4.48 2.52 7.18 1.63 5.84 1.47 9.89

pH* 11.9 11.92 11.99 11.94 12.09 11.31 11.66 10.72 11.42

Relative Density 3.11 3.07 3.10 3.02 3.08 3.07 3.07 3.02 3.03

Blaine (m2/kg) 367 365 399 364 430 379 394 391 421

45µm, % passing 95.7 92.5 94.9 89.2 94.0 96.0 96.1 96.2 96.5 Na2Oe: Na2O + 0.658 (K2O) fCaO: free lime LOI: Loss on ignition * based on w/b = 10 solution analysis @ 10 minutes

164

Table 4.9 Range for chemical and physical properties of Cement TII blends at 10% and

20% replacement (Theoretical calculation, mass %)

CKDs at 10% CKDs at 20% Fillers at 10% Fillers at 20%

Components TII TII replacement TII replacement TII replacement TII replacement

Min. Max Min. Max Min. Max Min. Max

SiO2 20.39 19.77 20.75 19.16 21.12 18.61 28.16 16.83 35.94

Al2O3 4.21 4.16 4.70 4.12 5.19 3.83 3.85 3.46 3.50

Fe2O3 3.01 2.86 3.08 2.72 3.16 2.71 2.73 2.42 2.45

CaO 63.06 60.02 62.34 56.99 61.62 56.75 62.10 50.45 61.14

MgO 3.21 2.99 3.20 2.77 3.19 2.89 2.95 2.57 2.68

SO3 2.98 2.98 4.30 2.99 5.61 2.68 2.68 2.39 2.39

Na2O 0.13 0.14 0.18 0.14 0.24 0.12 0.12 0.11 0.11

K2O 0.69 0.94 1.10 1.19 1.51 0.62 0.64 0.56 0.59

Na2Oe 0.58 0.75 0.89 0.92 1.20 0.53 0.54 0.48 0.50

Sol. Na2O 0.06 0.07 0.10 0.07 0.13 0.06 0.06 0.05 0.05

Sol. K2O 0.64 0.78 0.97 0.91 1.30 0.58 0.58 0.51 0.51

Sol. Na2Oe 0.49 0.58 0.72 0.67 0.96 0.44 0.44 0.39 0.39

TiO2 0.26 0.25 0.29 0.25 0.32 0.24 0.24 0.21 0.21

P2O5 0.12 0.11 0.12 0.10 0.13 0.11 0.11 0.10 0.10

Mn2O3 0.56 0.51 0.55 0.46 0.55 0.50 0.50 0.45 0.45

Cl 0.00 0.03 0.25 0.07 0.50 0.00 0.00 0.00 0.00

Ca(OH)2 1.30 1.17 1.66 1.04 2.02 1.17 1.17 1.04 1.04

fCaO 0.55 0.90 3.94 1.24 7.34 0.49 0.49 0.44 0.44

LOI 1.28 1.70 4.02 2.12 6.77 1.17 5.38 1.06 9.48

pH* 11.9 11.92 11.99 11.94 12.09 11.31 11.66 10.72 11.42


Blaine (m2/kg) 377 374 408 372 438 388 403 399 429

45µm, % passing 92.0 89.1 91.5 86.2 91.1 92.6 92.8 93.2 93.5 Na2Oe: Na2O + 0.658 (K2O) fCaO: free lime LOI: Loss on ignition * based on w/b = 10 solution analysis @ 10 minutes

165

An assessment of the CKD-PC blend compositions in comparison to the control PC alone

and control PC-filler blends provides insight into the potential influence of partial CKD

replacements of PC. The presence of CKDs causes the sulfate, alumina, alkalis,

portlandite, free lime, and chloride contents of the CKD-PC blends to generally be the

same or higher than that of the control PC alone and of control PC-filler blends. The

magnitude of the change for each component is important to consider in assessing the

potential impact of each component’s elevated concentration. The physical properties of

the CKD-PC blends are also important factors to consider.

PC performance is highly sensitive to small changes in sulfate content which can result in

very significant effects on hydration, strength development, and volume stability. The

sulfate contents of the CKD-PC blends change relative to the control mixes within a

range of -0.13% to +0.98% for the blends with Cement TI and 0.0% to 1.32% for the

blends with Cement TII. In relation to the sulfate content, the elevated alumina

concentrations could affect the optimum sulfate/alumina balance required for normal set

to occur. The factor most influencing the effect of calcium sulfate on the early reactions

is the rate at which the calcium and sulfate ions are made available in solution. Elevated

calcium concentrations during early stages of hydration due to increased free lime and

portlandite may allow the excess sulfates to combine with calcium to behave similarly to

calcium sulfate (gypsum).

Alkalis are widely reported to accelerate alite hydration, but this is only when the sulfate

levels were optimized. At sulfate levels above optimum, the acceleration effects of alkalis

were either reduced or suppressed. The presence of higher calcium, as well as alkali

concentrations, during early stages of hydration may also influence the solubility of

phases during early age hydration. Increased hydroxyl ions, as a result of portlandite and

alkalis, may also increase the potential for ASR.

166

With respect to chlorides, calcium chloride is the most effective for accelerating

hydration of C3S (Taylor, 1997). Bhatty (1984) suggested that CKD alkali chlorides

would behave similarly to calcium chloride. Chlorides are known to accelerate PC

hydration and dosages between 1 and 2% of PC content (by mass) are generally

recommended in the field for non-reinforced concrete. The maximum chloride

concentration within the CKD-PC blends, however, is only 0.50%. Therefore, optimal

acceleration of alite hydration would not be expected. The presence of chlorides could be

a concern for steel reinforcement corrosion in concrete. In EN-197, chloride contents of

cements are limited to 0.10%.

Additional free lime and calcium hydroxide has an important role to play in the initial

hydration of PC by supplying calcium ions to the system. Any change in the lime

concentration or displacement of the solubility equilibrium of portlandite – such as

addition of calcium salts or alkalis – may change the formation characteristics of C-S-H.

Soft burnt (highly reactive) free lime may increase water demand. Hard burnt free lime

raises a concern for soundness due to its delayed hydration.

The relative densities of the CKD-PC blends are similar to those of the control PC-filler

blends but lower than that of the control PC alone. An increase in the volume of solid

particles may impact rheological properties. The CKD-PC blends generally have higher

Blaine fineness values but lower percentage passing 45 µm. This implies that the CKDs

have a broader particle size range than PCs, with CKDs having higher amounts of both

very fine and coarse particles than PCs. The CKD-PC blends generally have similar

Blaine fineness values but lower percentage passing 45 µm in comparison to that of the

PC-filler blends. The fineness of the CKD-PC blends can broadly influence chemical

reactivity, rheological properties, volume stability, and durability.

167

4.2.1 Kinetics

4.2.1.1 Heat of Hydration

The rate of heat liberation on the recorded output is used as a means of measuring the rate

of hydration. Isothermal conduction calorimetry was used to assess the heat evolution of

pastes at 0%, 10%, and 20% replacement of Cements TI and TII, in accordance with

ASTM C1679. Six CKDs from different cement plants, a limestone powder, and a quartz

powder were used as the replacement materials. Each sample was performed at a w/b

ratio of 0.40 in duplicate to check the repeatability of the heat of hydration tests. The total

heat measurements of the duplicate tests were within ±3% of each other. The rates of heat

evolution during initial hydrolysis did vary somewhat but after the transition to the

induction period, the rates of heat evolution were essentially the same.

In order to create regression models for the influence of composition and fineness on

CKD-PC blends, a characterization system was developed for the heat liberation curves

as shown in Figure 4.6. The parameters of the heat curve that were used to characterize

the behaviour of hydration are: the total heat evolved during initial hydrolysis (Ai), the

minimum rate of heat evolution during the induction period (Qi), the time at which Qi

occurs (ti), the maximum rate of heat evolution (Qw), the rate of heat evolution between

the minimum rate of heat evolution during the induction period and the maximum rate of

heat evolution (Qw-Qi), and the cumulative heat evolution after initial hydrolysis over

seven days (A7d-Ai) (the cumulative heat evolution is simply the area under the rate

curve for the time under consideration).

168

Figure 4.6 Schematic of isothermal conduction calorimetry curve heat liberation

characterization

The rate of heat development curves for various time periods over seven days of

hydration are shown in Appendix E. The heat liberation curves indicate that the presence

of different CKDs is markedly different from the control PC alone and equivalent

amounts of limestone or silica flour as partial replacements of PC. The magnitude of the

peaks and the times at which they occur depends on the chemical, mineralogical, and/or

physical properties of each binder blend.

Sulfate Depletion Peak

A7d-Ai

169

The heat liberation curve of PC consists of a large initial peak represented by Ai. The Ai

for each control, CKD-PC blend, and PC-filler blend is presented in Figure 4.7. In

agreement with results reported by Wang et al. (2002), the CKD-PC blends had similar or

higher heat evolution during initial hydrolysis than the respective control cements. Based

upon Ai, it appears there is a similar or higher chemical reactivity during the initial

hydrolysis period in the CKD-PC blends than the respective cement alone controls. The

CKD-PC blends initial hydrolysis heat evolutions were similar to or higher than the PC-

filler blends at equivalent replacement levels. As the percentage of CKD replacement

increased from 10% to 20%, the total heat evolution remained similar or increased. The

blends with CKDs from preheater/precalciner processes, CKDs E and F, had the highest

heat evolution during initial hydrolysis in comparison to the respective PC control and all

blends with equivalent replacement of PC.

The main contributing factors that are reported to affect initial hydrolysis heat evolution

are (i) hydration of free lime, (ii) hydration of calcium sulfate hemihydrate to gypsum,

and (iii) formation of AFt, primarily from the aluminate phase but also from the ferrite

phase (Bensted, 1987). Since the initial dissolution of ions from CKDs are qualitatively

the same as from PCs, as shown in Section 4.1.4, the same factors that affect initial

hydrolysis of heat evolution for PCs are likely the same as those for CKD-PC blends.

Further, the mineralogical components of PCs that are known to affect initial hydrolysis

are the same as those found in CKDs.

The heat evolution Ai as a function of free lime content of the binder is shown for the two

control cements and CKD-PC blends in Figure 4.8. It appears the relationship for Ai is

linear with a positive slope for the binders as a function of free lime concentration greater

than 2% for both Cements TI and TII CKD blends. Scatter in the data for mixtures with

less than 2% free lime, however, indicates that factors other than free lime are also

involved.

170

(a)

0

5

10

15

10% replac ement 20% replac ement

Init

ial

Hy

dro

lys

is

(Ai)

He

at

Ev

olu

tio

n,

J/g

TII

TII L S

TII S L X

TII C K D A

TII C K D B

TII C K D C

TII C K D D

TII C K D E

TII C K D F

(b)

Figure 4.7 Cumulative heat of hydration during initial hydrolysis (Ai) of (a) Cement TI

blends and (b) Cement TII blends (w/b = 0.4, 23°C)

(The legends are ordered top (left) to bottom (right) for the bar charts)

0

5

10

15


Init

ial

Hy

dro

lys

is

(Ai)

He

at

Ev

olu

tio

n,

J/g

TI

TI L S

TI S L X

TI C K D A

TI C K D B

TI C K D C

TI C K D D

TI C K D E

TI C K D F

A B C

D

E

F

A

B

C

D

E

F

A B

C D

E

F

A B

C

D

E

F

TI

SLX LS

TI SLX LS

TII SLX

LS

TII

SLX LS

171

2.5

5

7.5

10

12.5

15

Ai, (

mW

/g.h

)

0 2 4 6 8

Free CaO, %

(a)

4

6

8

10

12

Ai, m

W/g

.h

0 2 4 6 8

Free CaO, %

(b)

Figure 4.8 Cumulative heat of hydration during initial hydrolysis (Ai) as a function of

Free CaO (%) for (a) Cement TI CKD blends and (b) Cement TII CKD blends (w/b =

0.4, 23°C)

10%

20%

Control

PC Replacement

r = 0.987

r = 0.956

10%

20%

Control

PC Replacement

172

In order to determine the influence of CKD-PC blends with less than 2% free lime

content, all blends with CKDs E and F were removed from the regression analysis. For

Cement TI blends, the initial heat evolution as a function of sulfate content of the binder

was linear with a positive slope, as shown in Figure 4.9(a). One possible reason for this is

that the increased quantity of sulfate ions from CKDs could lead to increased chemical

reaction with the Cement TI aluminate phase to form more AFt.

The Cement TII-CKD blend initial hydrolysis heat evolution as a function of the binder

alkali concentration was linear with a positive slope, as shown in Figure 4.9(b). The high

rate of dissolution of alkalis from the CKD fraction would likely increase the pH of the

liquid phase during initial hydrolysis. Dyer et al. (1999) suggested that the higher pH

levels produced by alkalis dissolving into solution from CKDs would likely promote

formation of more hydrates and lead to higher heat evolution during early age hydration.

173

4

5

6

7

8

Ai, J

/g

4 4.5 5 5.5 6 6.5 7

Sulfate, %

(a)

4

4.5

5

5.5

6

6.5

7

Ai (J

/g)

.4 .6 .8 1 1.2 1.4

Total Alkalis (NaEq), %

(b)

Figure 4.9 Cumulative heat of hydration during initial hydrolysis (Ai) as a function of (a)

sulfate content for Cement TI CKD blends and (b) alkali content for Cement TII CKD

blends (w/b = 0.4, 23°C)

r = 0.880

10%

20%

Control

PC Replacement

r = 0.866

10%

20%

Control

PC Replacement

174

The induction period, which follows the initial hydrolysis phase, is characterized by a

period of very little heat evolution. The minimum rate of heat evolution during the

induction period (Qi) of Cements TI and TII CKD blends is shown in Figure 4.10. The Qi

for Cement TI CKD blends were similar to or higher than that of the Cement TI control.

The Qi for Cement TII CKD blends, however, were both above and below that of the

Cement TII control. It appears the relationship for Qi is linear with a positive slope for

the binders as a function of sulfate concentration for both Cements TI and TII CKD

blends, as shown in Figure 4.11.

During the induction stage, the influence of increased sulfate concentration on the rate of

heat evolution is likely due to increased formation of AFt. The Cement TI CKD blends

have a higher correlation to the sulfate content than the Cement TII CKD blends. C3A

reacts with calcium and sulfate ions to form AFt. Since Cement TI has a higher C3A

content than Cement TII, this further indicates the likelihood of AFt formation as a

governing factor. The sulfate form of the CKD-PC binder influence on Qi is also

important. Figure 4.12 shows that Qi is also linear with a positive slope as a function of

calcium langbeinite for both Cement TI and TII blends.

175

0.0

0.5

1.0

1.5

2.0


Qi,

mW

/g

TI

TI L S

TI S L X

TI C K D A

TI C K D B

TI C K D C

TI C K D D

TI C K D E

TI C K D F

(a)

0.0

0.5

1.0

1.5

2.0


Qi,

mW

/g

TII

TII L S

TII S L X

TII C K D A

TII C K D B

TII C K D C

TII C K D D

TII C K D E

TII C K D F

(b)

Figure 4.10 Minimum heat of hydration rate during induction period (Qi) of (a) Cement

TI blends and (b) Cement TII blends (w/b = 0.4, 23°C)


A

B

C

D

E

F

A

B

C

D

E

F

A B

C

D E F

A B

C

D

E

F

TI SLX

LS TI SLX

LS

TII

SLX LS

TII

SLX LS

176

0.5

0.75

1

1.25

1.5

Qi, m

W/g

4 4.5 5 5.5 6 6.5 7

Sulfate, %

(a)

0.5

0.75

1

1.25

1.5

1.75

Qi, m

W/g

2.5 3 3.5 4 4.5 5 5.5 6

Sulfate, %

(b)

Figure 4.11 Minimum heat of hydration rate during induction period (Qi) as a function of

sulfate content for (a) Cement TI CKD blends and (b) Cement TII CKD blends (w/b =

0.4, 23°C)

r = 0.921

10%

20%

Control

PC Replacement

r = 0.765

10%

20%

Control

PC Replacement

177

0.5

0.75

1

1.25

1.5

1.75

Qi, m

W/g

0 .1 .2 .3 .4 .5 .6

Calcium Langbeinite, %

(a)

0.5

0.75

1

1.25

1.5

1.75

Qi, m

W/g

0 .1 .2 .3 .4 .5 .6


(b)

Figure 4.12 Minimum heat of hydration rate during induction period (Qi) as a function of

calcium langbeinite content for (a) Cement TI CKD blends and (b) Cement TII CKD

blends (w/b = 0.4, 23°C)

r = 0.908

10%

20%

Control

PC Replacement

r = 0.873

10%

20%

Control

PC Replacement

178

The time of the minimum rate heat evolution during the induction period (ti) for all

control blends is shown in Figure 4.13. The ti for CKD-PC blends occurred later than that

of the pastes with PCs alone and/or PC-filler blends. These findings were in agreement

with the results reported by Wang et al. (2002) using a CKD at 0, 15%, and 25%

replacement of an OPC. The relationship for ti is linear with a positive slope for the

binders as a function of total alkali concentration for both Cement TI and Cement TII

CKD blends, as shown in Figure 4.14.

Although there are many hypotheses regarding the mechanics of the induction phase,

many researchers advance that it is caused by formation of a protective layer on the C3S

particles inhibiting further hydration and terminates when this layer is destroyed or

rendered more permeable by aging or phase transformation (Gartner et al., 2002). It is

widely reported that alkalis accelerate hydration of C3S. It is important to note that this

effect, however, is only found in PCs with optimized sulfate content levels. The increased

alkali content of the CKD-PC blends, which were not optimized for sulfate content,

appeared to delay Qi. This indicates that CKD alkali content retarded the normal

hydration of C3S. One suggestion that could explain the correlation between the increased

alkali concentration and the delayed time of Qi (ti) is reduced solubility of C3S due to the

common ion effect (Gartner et al., 2002).

179

0.0

0.5

1.0

1.5

2.0

2.5


ti,

ho

urs

TI

TI L S

TI S L X

TI C K D A

TI C K D B

TI C K D C

TI C K D D

TI C K D E

TI C K D F

(a)

0.0

0.5

1.0

1.5

2.0

2.5


ti,

ho

urs

TII

TII L S

TII S L X

TII C K D A

TII C K D B

TII C K D C

TII C K D D

TII C K D E

TII C K D F

(b)

Figure 4.13 Time of minimum heat of hydration rate during the induction period (ti) of

(a) Cement TI blends and (b) Cement TII blends (w/b = 0.4, 23°C)


A

B

C D

E F A

B

C

D

E F

A

B

C

D

E

F

A

B C

D

E F

TI

SLX LS

TI

SLX

LS

TII SLX LS

TII SLX LS

180

1.25

1.5

1.75

2

2.25

2.5

ti, hours

.9 1 1.1 1.2 1.3 1.4 1.5 1.6


(a)

1

1.25

1.5

1.75

ti, hours

.4 .6 .8 1 1.2 1.4


(b)

Figure 4.14 Time of minimum heat of hydration rate during the induction period (ti) as a

function of total alkali content for (a) Cement TI CKD blends and (b) Cement TII CKD

blends (w/b = 0.4, 23°C)

r = 0.762

10%

20%

Control

PC Replacement

r = 0.825

10%

20%

Control

PC Replacement

181

Following the induction phase, an ascending rate of heat generation leads to the main

hydration peak. The ascending curve and the main hydration peak correspond to

hydration of the C3S. The CKDs generally do not possess high amounts of C3S that could

contribute to the main hydration peak. Any pozzolanic reaction that could occur is

typically not observed, if at all, until after the main hydration peak in isothermal

conduction calorimetry. Therefore, the main hydration peak of the CKD-PC blends can

be assumed to be mostly the C3S contribution of the PC. The magnitude of the main

hydration peak (Qw) is typically used to assess C3S hydration between different samples.

Since Qi varied significantly among the CKD-PC blends, the main hydration peak

relative to Qi (Qw-Qi) was used to assess the effects on C3S hydration during the

acceleration stage leading to the main hydration peak.

The Qw-Qi for each mix is shown in Figure 4.15. The Qw-Qi for the CKD-PC blends

varied widely, as many were both above and below the respective PC control. As the

percentage of CKD replacement increased from 10% to 20% for each CKD blend, the

Qw-Qi decreased. This effect was more pronounced in the Cement TI CKD blends than

in the Cement TII CKD blends. Blends with CKDs A, B, and E had the highest Qw-Qi

for both PCs within their respective 10% and 20% replacement categories. These CKDs

generally have higher chloride and lower sulfate contents than CKDs C, D, and F. The

dilution effect of PC appears as a reduction in the Qw-Qi. The magnitudes of the Qw-Qi

for blends with limestone and silica sand as partial replacement of PC were lower than

that of the control PCs alone and all CKD-PC blends with the same respective control

PC.

182

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0


Qw

- Q

i, m

W/g

TI

TI L S

TI S L X

TI C K D A

TI C K D B

TI C K D C

TI C K D D

TI C K D E

TI C K D F

(a)

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0


Qw

- Q

i, m

W/g

TII

TII L S

TII S L X

TII C K D A

TII C K D B

TII C K D C

TII C K D D

TII C K D E

TII C K D F

(b)

Figure 4.15 Main hydration peak relative to the minimum peak rate heat of hydration

during the induction period (Qw-Qi) for (a) Cement TI blends and (b) Cement TII blends

(w/b = 0.4, 23°C)


A B

C

D

E

F

A B

C

D

E

F

A

B

C D

E

F

A B

C

D

E

F

TI

SLX LS

TI

SLX LS

TII SLX

LS TII SLX

LS

183

The Qw-Qi had a good correlation with the calcium langbeinite content of the CKD-PC

blends, as shown in Figure 4.16. The Qw-Qi has a negative linear slope as a function of

calcium langbeinite content for both Cements TI and TII CKD blends. It is known that

the main hydration peak is generally depressed at gypsum (calcium sulfate) levels above

the optimum sulfate content (Lawrence, 1998b) and that there is significant C-S-H uptake

of sulfate ions. The decrease in Qw-Qi as the calcium langbeinite increased suggests that

the calcium langbeinite may be providing calcium and sulfate ions, similar to gypsum.

184

2

2.5

3

3.5

4

Qw

-Qi, m

W/g

0 .1 .2 .3 .4 .5 .6


(a)

2

2.5

3

3.5

4

Qw

-Qi, m

W/g

0 .1 .2 .3 .4 .5 .6


(b)

Figure 4.16 Main hydration peak relative to the minimum peak rate heat of hydration

during the induction period (Qw-Qi) as a function of calcium langbeinite content for (a)

Cement TI CKD blends and (b) Cement TII CKD blends (w/b = 0.4, 23°C)

r = -0.910

10%

20%

Control

PC Replacement

r = -0.786

10%

20%

Control

PC Replacement

185

Although calcium langbeinite seems to have a strong influence on the kinetics of C-S-H

formation, other components appear to also affect C3S hydration if sulfate levels are low.

The increased Qw-Qi for some of the CKD-PC blends is likely due to the presence of

chlorides that caused the main hydrate peak to be higher and narrower. As shown in

Figure 4.17(a), the high-chloride; low-sulfate CKD A at 10% replacement of Cement TI

caused the ascending slope to be steeper and narrower in comparison to LS at 10%

replacement of Cement TI. The low-chloride; medium-sulfate CKD C at 10%

replacement of Cement TI had little impact on the shape of the hydration curve from the

induction phase to the main hydration peak, as shown in Figure 4.17(b). This may be due

to low solubility of the sulfate in CKD C.

The heat of hydration curves for Cement TI at 0% (control) and 20% replacement with

LS are shown in Figure 4.17(c). The dilution effect of limestone is evidenced by a

reduction in the main hydrate peak. CKD B at 20% replacement of Cement TI appeared

to have a significant broadening immediately after the main hydration peak indicating

pozzolanic reactivity, as shown in Figure 4.17(d). This was likely due to the presence of

reactive fly ash in CKD B.

186

0.0

1.0

2.0

3.0

4.0

5.0

0 4 8 12 16 20 24

time (h)

heat

evo

luti

on

(m

W/g

)

TI CKD A 10%

TI LS 10%

0.0

1.0

2.0

3.0

4.0

5.0

0 4 8 12 16 20 24

time (h)

heat

evo

luti

on

(m

W/g

) TI CKD C 10%

TI LS 10%

(a) (b)

0.0

1.0

2.0

3.0

4.0

5.0

0 4 8 12 16 20 24

time (h)

heat

evo

luti

on

(m

W/g

)

TI

TI LS 20%

0.0

1.0

2.0

3.0

4.0

5.0

0 4 8 12 16 20 24

time (h)

heat

evo

luti

on

(m

W/g

)

TI CKD B 20%

TI LS 20%

(c) (d)

Figure 4.17 Heat of hydration for Cement TI with (a) CKD A and LS at 10%

replacements, (b) CKD C and LS at 10% replacements, (c) 0% and LS at 20%

replacements, and (d) CKD B and LS at 20% replacements (w/b = 0.4, 23°C)

187

The sulfate depletion (aluminate hydrate) peak for a properly retarded PC occurs after the

main hydration peak, as shown for Cement TI in Figure 4.18(a). The Cement TII heat

evolution aluminate peak, however, was superimposed on the main silicate hydration

peak, as shown in Figure 4.19(a). This implies that Cement TII does not have sufficient

available gypsum to retard the early hydration of aluminate phase. It appears the presence

of CKD retards or suppresses the time of the sulfate depletion peak for the CKD-PC

blends, as shown in Figure 4.18(b) and Figure 4.19(b, c). Calcium and sulfate ions in the

form of gypsum are known to retard the sulfate depletion peak by forming AFt. This

implies that CKD is contributing excess calcium and sulfate ions that are readily

available to react with C3A. Since calcium langbeinite appears to have a significant

influence on the early age of hydration during the induction phase, it is reasonable to

assume it can also affect the sulfate depletion peak. This is particularly important, since

the proposed mechanism for calcium langbeinite takes into account the rate at which the

sulfate phase can supply both calcium and sulfate ions to the surfaces of the aluminate

phases during early stage hydration (Tang and Gartner, 1988).

188

(a)

(b)

Figure 4.18 Heat of hydration for Cement TI with (a) 0% and LS at 10% replacements

and (b) CKD E and LS at 20% replacements (w/b = 0.4, 23°C)

0.0

1.0

2.0

3.0

4.0

5.0

0 4 8 12 16 20 24

time (h)

heat

evo

luti

on

(m

W/g

)

TI

TI LS 10%Sulfate depletion peak

0.0

1.0

2.0

3.0

4.0

5.0

0 4 8 12 16 20 24

time (h)

heat

evo

luti

on

(m

W/g

)

TI CKD E 20%

TI LS 20%

189

(a)

(b)

(c)

Figure 4.19 Heat of hydration for Cement TII with (a) 0% and LS at 10% replacements,

(b) CKD C and LS at 10% replacements, and (c) CKD C and LS at 20% replacements

(w/b = 0.4, 23°C)

0.0

1.0

2.0

3.0

4.0

5.0

0 4 8 12 16 20 24

time (h)

hea

t evo

luti

on

(m

W/g

)

TII

TII LS 10%

0.0

1.0

2.0

3.0

4.0

5.0

0 4 8 12 16 20 24

time (h)

heat

evo

luti

on

(m

W/g

)

TII CKD C 10%

TII LS 10%

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

5.0

0 4 8 12 16 20 24

time (h)

heat

evo

luti

on

(m

W/g

)

TII CKD C 20%

TII LS 20%

Sulfate depletion peak

190

The heat due to initial hydrolysis was subtracted from the total heat evolution (A7d-Ai) in

order to compare effects on C3S hydration. The total heat generation from the induction

period to seven days hydration (A7d-Ai) of all blends is shown in Figure 4.20. At 10%

replacement of PC, the CKD-PC blends A7d-Ai were similar to or lower than that of the

PC alone and PC-filler blends. At 20% replacement of PC, the CKD-PC blends were all

lower than PC alone. The A7d-Ai generally decreased as the amount of CKD and filler

replacements increased from 10% to 20%.

191

70

75

80

85

90


A 7

d -

Ai,

J/g

TI

TI L S

TI S L X

TI C K D A

TI C K D B

TI C K D C

TI C K D D

TI C K D E

TI C K D F

(a)

70

75

80

85

90


A 7

d -

Ai,

J/g

TII

TII L S

TII S L X

TII C K D A

TII C K D B

TII C K D C

TII C K D D

TII C K D E

TII C K D F

(b)

Figure 4.20 The total heat generation from induction period to 7 days hydration (A7d-Ai)

for (a) Cement TI blends and (b) Cement TII blends (w/b = 0.4, 23°C)


A

B C

D

E F

A B

C

D

E F

A

B

C D

E

F

A

B C

D

E

F

TI

SLX

LS TI SLX

LS

TII SLX

LS

TII

SLX

LS

192


4.xviii Cumulative heat generation during initial hydrolysis (Ai) increased between

6% and 120% (more than double) at 10% CKD replacement of PC in

comparison to the respective PC control. At 20% CKD replacement, the Ai

increased between 16% and 208% (more than triple).

4.xix Large and highly reactive amounts of free lime (> 20%), typically found in

CKDs from preheater/precalciner pyroprocesses, readily react with water;

this results in an exothermic reaction that contributes to higher heat

generation during initial hydrolysis in comparison to all other blends and

control cements.

4.xx For Cement TI (high C3A), reactivity with CKD sulfates appears to

contribute to higher heat generation during initial hydrolysis. This reaction

is likely to form AFt. For Cement TII (low C3A), the contribution of alkalis

from CKDs appears to increase heat generation during initial hydrolysis.

4.xxi For Cement TI CKD blends, the minimum rate of heat evolution during the

induction period (Qi) as a function of the binder sulfate content appears to

be a linear relationship with a positive slope. At 10% and 20% replacement

of Cement TI with CKD A, the Qi values were similar (±3%) to that of

Cement TI alone. At 10% and 20% replacement of Cement TI with CKD B,

the Qi values decreased by 5% and 10%, respectively, in comparison to

Cement TI alone. At 10% and 20% replacement of Cement TI with CKDs

C, D, E, and F, the Qi values increased in the range of 25% to 44% and 37%

to 104%, respectively. The increased heat evolution is likely due to the

formation of additional AFt in the Cement TI CKD blends.

193

4.xxii In contrast to Cement TI CKD blends, the Cement TII CKD blends Qi do

not have as strong a relationship with the sulfate content, which is likely due

to the lower C3A level in Cement TII that inhibits the formation of AFt. At

10% and 20% replacement of Cement TII with CKDs A and B, the Qi

values were lower (15-36%) than that of Cement TI alone. At 10%

replacement of Cement TII with CKD C, the Qi value decreased by 8% but

at 20% replacement increased by 36% in comparison to Cement TII alone.

At 10% and 20% replacement of Cement TII with CKDs D, E, and F, the Qi

values increased in the range of 15% to 47% and 28% to 81%, respectively.

4.xxiii The Qi as a function of calcium langbeinite content of the binder appears to

be a linear relationship with a positive slope. This may indicate that the

sulfate form of CKDs contributing to AFt formation during the induction

period is largely due to calcium langbeinite.

4.xxiv The time of the minimum rate of heat during the induction period (ti) for

CKD-PC blends occurred later than that of the pastes with PCs alone. At

10% and 20% CKD replacement of Cement TI and Cement TII, the ti

increased by 13-58% and 29-85%, respectively. In contrast to the CKD-PC

blends, the PC-filler blends ti ranged between -5% and +18% in comparison

to the PC alone.

4.xxv The time of the minimum rate of heat during the induction period (ti) as a

function of the binder alkali content appears to be a linear relationship with

a positive slope. This indicates that CKD alkali content retards the normal

hydration of C3S.

194

4.xxvi The main hydration peak relative to the minimum rate of hydration during

the induction period as a function of the calcium langbeinite content is a

linear relationship with a negative slope. This indicates that the calcium

langbeinite content from CKD inhibits the hydration of C3S.

4.xxvii The sulfate depletion peak that occurs as a result of conversion of AFt to

AFm formation is delayed or suppressed by partial replacement of CKDs for

both PCs with all CKDs, except CKD A. The delay or suppression of AFt to

AFm appears to be due to the increased availability of calcium and sulfate

ions, which simulates the addition of gypsum to the blends.

4.xxviii At 10% replacement of Cement TI and TII with CKD, heat evolutions over

a seven-day period are similar (±5%) or lower (<8%) than the respective PC

control. At 20% replacement of Cement TI and TII with CKD, heat

evolutions decreased between 4% and 14% in comparison to the respective

control PC.

195

4.2.2 Physical Properties of Hydration

4.2.2.1 Normal Consistency

The purpose of the normal consistency test (ASTM C187) was to assess whether CKDs

varied the water demand of the CKD-PC blend pastes. Normal consistency is the water to

binder ratio required to bring the paste to a standard condition of wetness for which the

penetration of a standard needle (Vicat needle) into the paste is 10 ± 1 mm at 30 seconds.

To provide an indication of the sensitivity of the test, the results of the iterative process to

determine the water requirement for normal consistency of Cements TI and TII are

presented in Table 4.10. These results show that as little difference as 0.2% in the normal

consistency water demand can result in a paste that is outside the required range of 10mm

± 1 penetration at 30 seconds.

Table 4.10 Iterative process to determine the water requirement for normal consistency of

(a) Cement TI and (b) Cement TII

(a)

Cement w/b ratio (%) Needle Penetration

(mm)

TI 26.5 12

TI 26.2 8.5

TI 26.4 10

(b)

Cement w/b ratio (%) Needle Penetration

(mm)

TII 24.6 14.5

TII 23.7 6.5

TII 24.1 14

TII 23.8 8

TII 24.0 10

196

The normal consistency water demand results for the PC alone, CKD-PC blends, and PC-

filler blends are shown in Figure 4.21. At 10% replacement of Cements TI and TII, all of

the CKD-PC blends required more water to maintain a normal consistency penetration in

the range of 9 and 11 mm than the respective PC alone. At 20% replacement, each CKD-

PC blend required more water than each 10% replacement blend. Some CKD blends at

20% replacement required less water than CKD blends at 10% replacement with

equivalent PC. The blends with CKDs from preheater/precalciner processes – CKDs E

and F – had the highest water requirement for normal consistency in comparison to the

respective PC control and blends with equivalent replacement of PC. Previous

researchers (El Aleem et al., 2005; Ramakrishnan, 1990; Bhatty, 1984 and 1985a), who

also used normal consistency to study effects of CKD replacement at 10% and/or 20%,

had similar results.

Table 4.11 provides the range for increased water demand of blends with CKDs and

fillers in comparison to the PCs at equivalent replacement levels. At 10% and 20%

replacement of Cements TI and TII, the water requirement increase ranged between 0.1

and 0.7% for SLX and LS. At 10% replacement of Cement TI CKDs A, B, C, and D, the

increase in water demand (0.4 – 0.8%) was similar to or higher than the fillers effect on

the increase in water demand (0.1 – 0.4%). All other CKDs required more water than that

of the fillers as equivalent partial replacements of the same PC.

The blends with CKDs from the preheater/precalciner cement processes were separated

from the remaining CKD blends, since the impact was markedly different. For example,

Cement TI required 26.4% water to maintain normal consistency. At 10% replacement of

Cement TI, the water requirement increase ranged between 0.4 and 0.8% for CKDs A, B,

C, and D. CKDs E and F, however, resulted in an increase between 1.3 and 2.1%. The

water demand impact of CKD replacements was larger in magnitude in the Cement TII

blends than Cement TI blends. This suggests that the magnitude of impact is dependent

upon the composition of both the CKD and PC.

197

20%

22%

24%

26%

28%

30%

32%


Wa

ter

of

No

rma

l C

on

sis

ten

cy

(%

)

TI

TI L S

TI S L X

TI C K D A

TI C K D B

TI C K D C

TI C K D D

TI C K D E

TI C K D F

(a)

20%

22%

24%

26%

28%

30%

32%


Wa

ter

of

No

rma

l C

on

sis

ten

cy

(%

) TII

TII L S

TII S L X

TII C K D A

TII C K D B

TII C K D C

TII C K D D

TII C K D E

TII C K D F

(b)

Figure 4.21 Water requirement for normal consistency of (a) Cement TI blends and (b)

Cement TII blends


A B C D

E

F

A B

C D

E

F

A B C

D

E

F

A B C D

E

F

TI SLX LS

TI SLX LS

TII SLX LS TII SLX LS

198

Table 4.11 Range of change in water demand for normal consistency of pastes

PC % CKD

and Filler

Replacement

Fillers

w/b change

CKDs A, B, C, D

w/b increase

(CKDs from wet

and long-dry kilns)

CKDs E, F

w/b increase

(CKDs from

preheater/precalciner kilns)

10% 0.1% to 0.4% 0.4% to 0.8% 1.3% to 2.1% TI (26.4%)

20% 0.2% to 0.7% 1.1% to 1.6% 3.9% to 5.2%

10% 0.2% 1.2% to 1.6% 2.3 to 2.7% TII (24.0%)

20% 0.5% 2.3% to 2.7% 5.2% to 7.5%

Figure 4.22(a) shows the correlation of the normal consistency between all Cement TI

and Cement TII CKD blends. Figure 4.22(b) shows the same correlation with the

exception that blends with CKDs E and F were excluded. The very good correlation of

both indicates that the effects on normal consistency are a function of the CKD

composition.

Correlations between water demand for consistency of CKD-PC blends and various

independent variables were then conducted. The normal consistency water requirement as

a function of free lime for both Cement TI and TII CKD blends is shown in Figure 4.23.

The CKD-PC blends with the highest free limes also have the highest water demand. The

increased water demand, however, is not only due to the presence of high amounts of free

lime but also its reactivity. The free lime of preheater/precalciner process CKDs is

typically very reactive due to the low de-carbonation temperature, resulting in soft burnt

free lime. As discussed in Section 4.2.1.1, CKDs E and F have large amounts of very

reactive free lime, which is indicated by isothermal conduction calorimetry in the heat

evolved during initial hydrolysis.

199

0.22

0.24

0.26

0.28

0.3

0.32

TII C

KD

ble

nds

Norm

al C

onsis

tency (

%)

.26 .27 .28 .29 .3 .31 .32

TI CKD blends

Normal Consistency (%)

(a) Blends with all CKDs

0.22

0.24

0.26

0.28

0.3

0.32

TII C

KD

s (

A, B

, C

, D

)

Norm

al C

onsis

tency (

%)

.26 .265 .27 .275 .28 .285

TI CKDs (A, B, C, D)

Consistency (%)

(b) Blends with CKDs A, B, C, and D

Figure 4.22 Correlation between Cement TI and Cement TII blends with the same CKD

and replacement level for (a) all CKDs and (b) CKDs A, B, C, and D

r = 0.982

10%

20%

Control

PC Replacement

r = 0.967

10%

20%

Control

PC Replacement

200

0.22

0.24

0.26

0.28

0.3

0.32

w/b

@ N

orm

al C

onsi

stency,

%

0 2 4 6 8

Free CaO, %

(a)

0.22

0.24

0.26

0.28

0.3

0.32

w/b

@ N

orm

al C

onsis

tency, %

0 2 4 6 8

Free CaO, %

(b)

Figure 4.23 Water requirement for normal consistency as a function of free lime content

for (a) Cement TI CKD blends and (b) Cement TII CKD blends

r = 0.970

10%

20%

Control

PC Replacement

r = 0.958

10%

20%

Control

PC Replacement

201

The reason(s) for the effects of long-dry and wet kiln CKDs A, B, C, and D on increased

water demand in CKD-PC blends are not as clearly related to free lime. Attempts to

correlate water demand of the CKD-PC blends with CKDs A, B, C, and D to other

independent variables did not provide clear relationships. Since CKDs vary significantly

in composition, it is possible that there is more than one independent variable of CKD

that is impacting the water requirement. Besides the presence of free lime, an increase in

rate of ion dissolution could lead to greater overall chemical reactivity that requires

higher water demand.


4.xxix For Cement TI and Cement TII, 10% replacement with CKDs A, B, C, and

D (wet and long-dry kiln CKDs) increased water demand by 1 – 3% and 5 –

7%, respectively. At 20% replacement of Cement TI and Cement TII, water

demand increased by 4 – 6% and 10 – 11%, respectively.

4.xxx CKDs with large amounts of highly reactive free lime (CKDs E and F) at

10% replacement of Cement TI and Cement TII increased the water demand

by 5 – 8% and 11 – 17%, respectively. At 20% replacement of Cement TI

and Cement TII with CKDs E and F, water demand increased by 15 – 20%

and 22 – 31%, respectively.

4.xxxi As the percent replacement of PC increased from 10% to 20% for CKDs A,

B, C, and D, water demand increased by 2 – 3% for Cement TI and 4 – 5%

for Cement TII, in comparison to the PC control. As percent replacement of

PC increased from 10% to 20% for CKDs E and F, water demand increased

by 9 – 11% for Cement TI and 10 – 12% for Cement TII. As filler

replacement levels increased from 10% to 20% of PC, the water demand

remained the same (± 1%).

202

4.2.2.2 Flow

The purpose of the flow test was to assess the impact of CKDs on the workability of the

CKD-PC mortar blends. A minimum of two flow measurements were taken for the PCs

and with CKD and filler as partial replacements of the PCs at a constant w/b ratio of

0.485. The average of the measurements for each mortar control and mortar blend is

presented in Figure 4.24. The statistical differences among the mortars for Cements TI

and TII were assessed using one-way analysis of variance (one-way ANOVA) and results

are presented in Appendix F.

Generally, the filler replacements increased flow while the CKD replacements reduced

flow. This indicates that the behaviour of the fillers is different from the impact of CKDs.

The LS and SLX blends had higher flow measurements at both 10% and 20%

replacement than that of the respective control PCs. As the percentage of each filler

replacement increased from 10% to 20% for both Cements TI and TII, the flow increased.

As the percentage of each CKD replacement increased from 10% to 20%, however, the

flow decreased. Some of the CKD blends at 20% replacement, however, had higher flow

than some CKD blends at 10% replacement with equivalent PC. The governing influence

of using CKD as a partial replacement of PC does not appear to be the percentage of

replacement.

At 10% replacement of Cement TI the flow of CKD blends were all lower than the

control with the exception of the blend with CKD D. The Cement TI with 10% CKD D

had a similar flow measurement to both filler blends at 10% replacement. However, at

20% replacement, all Cement TI CKD blends were lower than both the Cement TI alone

and filler blends. All Cement TII CKD blends had similar flow or were lower than that of

the Cement TII alone. Blends with CKD D had the highest flow in comparison to the

other CKD blends at an equivalent replacement level, while blends with the

preheater/precalciner CKDs E and F had significantly reduced flow.

203

50

60

70

80

90

100

110

120


Flo

w

TI

TI L S

TI S L X

TI C K D A

TI C K D B

TI C K D C

TI C K D D

TI C K D E

TI C K D F

(a)

50

60

70

80

90

100

110

120


Flo

w

TII

TII L S

TII S L X

TII C K D A

TII C K D B

TII C K D C

TII C K D D

TII C K D E

TII C K D F

(b)

Figure 4.24 Mortar flow of (a) Cement TI blends and (b) Cement TII blends


A B

C

D

E

F

A

B C

D

E

F

A

B C

D

E

F

A

B

C

D

E

F

TI

SLX LS

TI

SLX LS

TII SLX LS

TII SLX

LS

204

The ASTM C109 requirement for mortar flow is 110 ± 5 of blended cement. The range of

flows for the filler and CKD blends at 10% and 20% for each PC are presented in Table

4.12. Cement TI control flow was 107, which is close to the lower limit of the required

range. Cement TII control flow was 114, however, which is close to the upper limit of the

required range. The flows of PC-filler blends were comparable (±3) at equivalent partial

replacements of the same PC. Filler replacements at 10% of Cement TI were within the

ASTM range, while all other blends with filler replacements were near or slightly above

the upper limit.

Blends with CKDs A, B, C, and D were separated from blends with CKDs E and F due to

the significant difference in the range of flows. At 10% replacement of Cement TI with

CKDs A, B, C, and D the flow measurements were all within the required range or

slightly below the lower limit. Cement TII blends with CKDs A, B, C, and D at 10%

replacement were all within the required range. At 20% CKD replacements of Cements

TI and TII, all blends were slightly above or below the lower limit of 105, with the

exception of Cement TI CKD B at 20% that had a flow of 95. Blends with CKDs E and F

at 10% replacement of PCs were only slightly below the lower limit, except for Cement

TI CKD F at 10% replacement, which was 94. Blends with CKDs E and F at 20%

replacement of Cements TI and TII, however, were well below the ASTM specified

range.

Table 4.12 Range of flow for all mortars

CKD

Replacement

Cement

Type

CKDs A, B, C, D

(CKDs from wet and

long-dry kilns)

Flow Range

CKDs E, F

(CKDs from

preheater/precalciner kilns)

Flow Range

Fillers

Flow Range

TI (107) 100 – 110 94 – 102 111 – 112 10 % replacement

TII (114) 109 – 113 100 – 103 116 –117

TI (107) 95 – 108 66 – 79 114–117 20% replacement

TII (114) 102 – 109 78 – 90 117–118

• Regular: All flows between 105 - 115

• Italic: All flows between 100 – 120

• Bold: Atleast one flow is below 100

205

Correlations between flow of CKD-PC blends and various independent variables were

conducted. The flow as a function of free lime for both Cement TI and TII CKD blends is

shown in Figure 4.25. Similar to the impact on water requirement for normal consistency,

the CKD-PC blends with the highest free lime contents also have the highest water

demand, resulting in low flow. As discussed in Sections 4.2.1.1 and 4.2.2.1, high amounts

of reactive free lime in CKDs E and F quickly combine with water to form calcium

hydroxide precipitates. The reduction in flow is likely due to the formation of these

precipitates. Scatter in the data below 2% free lime, however, indicates that factors other

than free lime are also involved.

Correlations were then investigated for flow of CKD blends excluding CKDs E and F and

other independent variables. As shown in Figure 4.26, the effects of fineness became

more pronounced for both Cements TI and TII CKD blends. The most pertinent findings

of the analysis are that the flow correlates well with the particle size fraction less than 30

µm for Cement TI CKD blends and less than 45 µm for Cement TII CKD blends. As the

percentage of finer particles below the respective size increases, so does the flow. This

apparently is in line with the results of the fillers, which also have higher 45 µm passing

and higher flow. CKD D also had the highest percentage of particles passing 45 µm and

the highest flows.

206

60

70

80

90

100

110

120

Flo

w

0 2 4 6 8

Free CaO, %

(a) Cement TI blends

60

70

80

90

100

110

120

Flo

w

0 2 4 6 8

Free CaO, %

(b)

Figure 4.25 Mortar flow as a function of free lime content for (a) Cement TI CKD blends

and (b) Cement TII CKD blends

(Encircled data points reflect scatter in the data below 2% free lime content)

r = -0.870

10%

20%

Control

PC Replacement

r = -0.926

10%

20%

Control

PC Replacement

207

90

95

100

105

110

115

Flo

w

74 75 76 77 78 79

Volume < 30.5 µm, %

(a)

100

102.5

105

107.5

110

112.5

115

Flo

w

86 87 88 89 90 91 92 93

45µm, % Passing

(b)

Figure 4.26 Mortar flow as a function of (a) percentage of volume less than 30.5 µm for

Cement TI CKD blends (excluding CKDs E and F) (b) percentage passing 45 µm for

Cement TII blends (excluding CKDs E and F)

r = 0.960

10%

20%

Control

PC Replacement

r = 0.892

10%

20%

Control

PC Replacement

208

The results from the present study indicate that the flows of CKD-PC mortar blends are

similar to or lower than PC alone. The role of CKD in reducing flow arises from the fact

that reactive free lime hydrates readily to form calcium hydroxide precipitates and/or

there is a smaller percentage of particle size less than 30.5 µm for Cement TI CKD

blends and 45 µm for Cement TII CKD.


4.xxxii The CKD-PC blends had similar (±5%) or reduced flows (>5% reduction) in

comparison to the control PC alone. The PC-filler blends, however, had

similar or higher flows (2 – 9%) than PC alone.

4.xxxiii At 10% and 20% replacement of Cement TI with CKDs A, B, and C, flow

decreased by 3 – 7% and 5 – 11%, respectively. At 10% and 20%

replacement of Cement TI with CKD D, flow was similar to the respective

PC control (±3%). At 10% and 20% replacement of Cement TII with CKDs

A, B, C, and D, flow decreased by 1 – 4% and 4 – 11%, respectively.

4.xxxiv CKDs with large amounts of highly reactive free lime reduce the flow of a

CKD-PC blend significantly in comparison to control PC. At 10%

replacement of Cement TI and Cement TII with CKDs E and F, flow

decreased by 5 – 12% and 10 – 12%, respectively. At 20% replacement of

Cement TI and Cement TII with CKDs E and F, flow decreased by 26 –

38% and 21 – 32%, respectively.

4.xxxv In the absence of large amounts of highly reactive free lime (>20%), it

appears the flow is governed by the fineness properties of the blends.

Cement TI CKD blend flows as a function of the total particles of less than

30.5 µm by volume is a linear relationship with a positive slope. For Cement

209

TII CKD blends, the flow as a function of percentage of the total particles

less than 45 µm by mass is a linear relationship with a positive slope.

4.xxxvi As the percentage of PC replacement with CKDs A, B, C, and D increased

from 10% to 20%, the flow remained the same or decreased by 0-5% for

Cement TI and decreased by 3 – 9% for Cement TII. As the percentage

replacement of PC with CKDs E and F increased from 10% to 20%, the

flow decreased by 23 – 30% for Cement TI and 13 – 22% for Cement TII.

As the percentage of PC replacement with fillers increased from 10% to

20%, however, the flow marginally increased (1 – 4%).

210

4.2.2.3 Initial Setting Time

Concrete is traditionally a mixture of PC, water, and aggregate. The initial setting time of

PC is important as, in addition to workability, it provides an indication of how long the

mixture will remain in the plastic condition to allow for its transportation, placement, and

compaction under a variety of conditions. For economic and logistical reasons, it is

generally desirable for concrete to harden and develop strength within a reasonable time

after it has been placed. For these reasons, understanding the impact of CKD as a partial

replacement of PC on the initial setting time is essential.

The ASTM C191 procedure was modified to attain a setting time at five minute intervals

instead of 15 minute intervals. To assess the repeatability of the initial setting time

results, three samples for each control PC were tested. The setting times for Cement TI

were 120, 115, and 120 minutes. The setting times for Cement TII were 60, 55, and 60

minutes. This provides an indication of the level of repeatability to be expected in the

results of the setting times for all blends.

The setting times for the PC alone, CKD-PC blends, and PC-filler blends are shown in

Figure 4.27. The blends with LS and SLX had very similar setting times to that of the

respective cement alone specimens. Of the 14 Cement TI CKD blends, nine exhibited

similar or delayed setting times in comparison to that of the Cement TI control. Cement

TI CKD blends that consisted of CKDs C and D at both 10% and 20% replacement had

shorter setting times in comparison to Cement TI alone. CKD F at 10% replacement of

Cement TI delayed setting time, but at 20% replacement shortened setting time in

comparison to the Cement TI control. All of the setting times for the Cement TII CKD

blends were delayed in comparison to the control. The setting times of CKD-PC blends

increased or stayed the same when the level of CKD replacement increased from 10% to

20%, except blends with CKD F.

211

0

20

40

60

80

100

120

140

160

180


Init

ial

Se

t T

ime

(m

inu

tes

)

TI

TI L S

TI S L X

TI C K D A

TI C K D B

TI C K D C

TI C K D D

TI C K D E

TI C K D F

(a)

0

20

40

60

80

100

120

140


Init

ial

Se

t T

ime

(m

inu

tes

)

TII

TII L S

TII S L X

TII C K D A

TII C K D B

TII C K D C

TII C K D D

TII C K D E

TII C K D F

(b)

Figure 4.27 Initial set time for (a) Cement TI blends and (b) Cement TII blends


A

B

C D

E F

A

B

C D

E

F

A B

C D

E

F

A

B

C D

E

F

TI SLX LS TI SLX

LS

TII

SLX LS

TII SLX LS

212

ASTM C150 allows the use of processing additions to meet the requirements of ASTM

C465 for use in the manufacture of hydraulic cements and states that the time of setting

(ASTM C191) shall not vary from that of the control cement by more than 60 minutes or

50%, whichever is the lesser. This requirement for setting time is one parameter that was

used to assess the acceptability of using CKDs as a partial replacement of PC in the

current standards.

The Cement TI control setting time was 120 minutes and, according to ASTM C465, the

acceptable setting time range for Cement TI with processing additions is between 60 and

180 minutes. All of the Cement TI CKD blends at both 10% and 20% replacement were

within the ASTM C465 specified range. The setting time with 10% CKD replacement of

Cement TI was between 105 and 130 minutes. The range of setting time with 20% CKD

replacement of TI was between 110 and 170 minutes.

The Cement TII setting time was 60 minutes and, according to ASTM C465, the

acceptable setting time range for Cement TII with processing additions is between 30 and

90 minutes. Three of the six Cement TII blends at 10% CKD replacement and two of the

six blends at 20% CKD replacement were within the acceptable range. The range of

setting times with 10% CKD replacement of Cement TII was between 70 and 100

minutes. The range of setting times with 20% CKD replacement of Cement TII was

between 80 and 125 minutes.

It is generally accepted that initial setting is controlled by the hydration of C3S to form C-

S-H. Under normal conditions, initial setting time and the transition from the heat of

hydration induction phase to the acceleration phase are related. Since it is difficult to

define this transition phase of the heat of hydration curve, the time at which the minimum

rate of heat evolution during the induction period, ti, is used as an indication of the time

at which the induction period occurs. The setting time as a function of the time of the

213

minimum rate of heat evolution during the induction period for both Cements TI and TII

CKD blends is shown in Figure 4.28.

As shown in Figure 4.28(a), the Cement TI CKD blends setting times correlate well with

the time that the minimum peak of the induction period occurred for blends that had

longer setting times than the TI control, indicating normal setting. The relationship

appears to be linear with a positive slope. The Cement TI CKD blends that resulted in

shorter setting times (TI CKD C 10 and 20%, TI CKD D 10 and 20%, and TI CKD F

20%), in comparison to Cement TI control, are circled in Figure 4.28(a). These data

points do not correlate well with time of the minimum rate of heat evolution during the

induction period. This indicates abnormal setting, which is typically caused by an

imbalance between alumina and sulfate ions. False set (a type of abnormal set) in the

Cement TI CKD blends with CKDs C and D is likely. This is due to either an excess of

sulfate in the liquid phase leading to secondary gypsum formation or excessive AFt

formation. CKD F was the only CKD that resulted in shortened settings times as the

replacement of both PCs increased from 10% to 20% replacement. These shortened

setting time are likely due to the large amount of highly reactive free lime resulting in

precipitation of Ca(OH)2 that causes an abnormal set similar to a flash set.

Figure 4.28(b) shows a strong relationship between the heat of hydration induction period

and the setting times for Cement TII CKD blends. Therefore, CKD F at 20% was

removed from the data set. The setting time as a function of the time of the minimum rate

of heat evolution during the induction period appears to be a linear relationship with a

positive slope, unless false or abnormal setting occurs. This indicates the difference

between hydration kinetics and the setting mechanism. This further reinforces false

setting as the case because normal setting is governed by C-S-H formation, which is

exhibited in the heat of hydration curve.

214

(a)

(b) Cement TII blends

(b)

Figure 4.28 Initial set time as a function of the time of minimum heat rate during the

induction period (ti) for (a) Cement TI CKD blends (excluding circled data points) and

(b) Cement TII CKD blends

40

60

80

100

120

140

Se

ttin

g t

ime

, m

inu

tes

1 1.25 1.5 1.75

time of induction, hours

100

120

140

160

180

Se

ttin

g t

ime

, m

inu

tes

1.25 1.5 1.75 2 2.25 2.5

time of induction, hours

r = 0.826

10%

20%

Control

PC Replacement

r = 0.795

10%

20%

Control

PC Replacement

Abnormal Set: TI CKD C 10% and 20% TI CKD D 10% and 20% TI CKD F 20%

215

Cement TII had a very short setting time, by industry standards. The paste false set test

(ASTM C451) was performed that indicated the short setting time was not due to false

set, but simply a quick set. As discussed in Section 4.2.1.1, the heat of hydration curves

for Cement TII showed that the sulfate depletion peak was superimposed on the main

hydration peak. This is an indication that inadequate soluble sulfate was available to

control the hydration of C3A to allow for normal setting to occur. It is likely that the early

sulfate depletion contributed to the hydration of C3A resulting in the quick set.

The setting time as a function of the soluble alkali content of the binder is shown in

Figure 4.29 for Cement TI CKD and Cement TII CKD blends. Although the setting is

influenced by many variables, the soluble alkali content of the CKD-PC blend is typically

of the greatest significance. Both time of induction from heat of hydration graphs and

initial setting times also correlate well with the alkali contents for the respective Cement

TI and Cement TII CKD blends. This strengthens the premise that alkalis retard the

normal hydration of C3S.

While, alkalis are widely reported to accelerate hydration of C3S, Osbaeck and Jons

(1980) stated that the accelerated effects of alkalis are diminished or absent if gypsum

(calcium sulfate) levels are above the optimum sulfate content. The present study

indicates that the sulfate contribution from CKDs behave similar to gypsum. Since CKDs

generally contain higher amounts of soluble sulfate than PC, the CKD-PC blends have

sulfate contents that are above the optimum sulfate level. Therefore, the finding that an

increase in alkali contribution from CKDs delays, rather than accelerates, hydration of

C3S is reasonable.

It is widely known that an increase in w/b for a given paste results in longer setting times.

Although the w/b ratio was higher for all CKD-PC blends than the PC, a relationship

between w/b and the setting times was not found. This finding is reasonable, however,

216

since the established influence of w/b refers to its effect on a single blend and not on

blends with different chemical/mineralogical and physical properties.

(a)

(b)

Figure 4.29 Initial set time as a function of soluble alkali content for (a) Cement TI

blends (excluding circled data points) and (b) Cement TII blends

r = 0.945

10%

20%

Control

PC Replacement

100

120

140

160

180

Se

t tim

e -

initia

l

.7 .8 .9 1 1.1 1.2 1.3

Sol. Alkalis (NaEq)

40

60

80

100

120

140

Se

t tim

e -

initia

l

.4 .5 .6 .7 .8 .9 1

Sol. Alkalis (NaEq)

r = 0.790

10%

20%

Control

PC Replacement

Abnormal Set: TI CKD C 10% and 20% TI CKD D 10% and 20% TI CKD F 20%

217


4.xxxvii All of the Cement TI CKD blends at both 10% and 20% replacement were

within the ASTM C465 specified range. At 10% CKD replacement of

Cement TI, the initial setting times were ±12.5% of the Cement TI initial

setting time. At 20% CKD replacement of Cement TI, the initial setting

times were between 8% shorter and 42% longer than the initial setting

time of Cement TI. Three of the six Cement TII blends at 10% CKD

replacement and two of the six blends at 20% CKD replacement were

within the acceptable range. At 10% and 20% CKD replacement of

Cement TII, the initial setting times were 17 – 67% and 33 – 108% longer,

respectively, than the initial setting time of Cement TII.

4.xxxviii The setting time as a function of the binder alkali content appears to be a

linear relationship with a positive slope, unless abnormal setting occurs.

This implies that an increase in the CKD alkali content retards the normal

setting process that occurs as a result of C-S-H hydration.

4.xxxix Abnormal setting may occur with some CKDs as partial replacements of

PCs, which is likely due to excessive amounts of sulfate ions available

during early age hydration. The likely precipitates are AFt and/or calcium

sulfate. Large amounts of highly reactive free lime in CKDs may cause

precipitation of calcium hydroxide and also result in abnormal/early

setting times.

4.xl Initial setting time is delayed by the presence of CKDs, unless abnormal

initial set occurs. All Cement TI CKD blends met the ASTM C465

standards for setting time at 10% and 20% replacement. For the Cement

TII CKD blends, however, only some of the blends at 10% and 20% CKD

218

replacement levels were within the acceptable range. The difference is

perhaps due to the relatively large change in alkali content between the

Cement TII CKD blends and Cement TII in comparison to the Cement TI

CKD blends and Cement TI.

4.xli It is widely known that an increase in w/b for a given paste results in

longer setting times. Although the w/b ratio was higher for all CKD-PC

blends than for the PC control, a relationship between w/b and the setting

times was not found. This finding is reasonable since the established

influence of w/b refers to its effect on a single blend and not on blends

with different chemical/mineralogical and physical properties.

4.2.2.4 Compressive Strength

Compressive strength is perhaps the most important criterion for assessing PC quality.

Virtually every PC testing specification stipulates minimum strength requirements at

certain ages. The strength development of a cementitious system is influenced by the PC

type or, more specifically, the mineralogical and physical properties of the PC. As the

effects of CKD-PC blends on strength in comparison to the control PC are considered, it

is also important to assess the performance criterion for the CKD-PC blends in meeting

industry standards.

The compressive strengths of all mortars were determined at 1, 3, 7, 28, and 90 days. The

compressive strength at each age was determined using an average of three cube

measurements at a constant w/b ratio of 0.485. The statistical differences among the

mixes were assessed using one-way analysis of variance (one-way ANOVA), and they

are presented in Appendix G.

The average compressive strengths for each mortar control and blend are presented in

Figure 4.30 and Figure 4.31 and tabulated in Table G.2. The range of the CKD-PC and

219

PC-filler blend strengths are presented as a percentage of values for PC alone at each age

in Table 4.13 and Table 4.14. ASTM C150 states that PC must meet minimum

compressive strength requirements that increase at later ages. ASTM C465 states that

mortar compressive strengths (ASTM C109) of blends with partial replacement of PC

shall not be less than 95% of the control PC at all ages. Therefore, 95% of PC

compressive strength at the same age is considered an adequate level to assess

performance of the CKD-PC blends.

At 10% replacement of Cement TI (Figure 4.30a), all CKD-PC blends were more than

95% of the PC control except the blend with CKD D at the age of one day (73%). At 10%

replacement of Cement TII (Figure 4.31a), the lowest compressive strength of the CKD-

PC blends was only marginally below the 95% threshold of PC alone at all ages, with the

lowest at 93%. It should be noted that many of the CKD-PC blends at 10% CKD

replacement level of PC were higher than the respective PC alone at the same age, with

the highest at 115% for the Cement TI CKD blends and 112% for the Cement TII CKD

blends.

At 20% replacement of the PCs with CKDs, the range of CKD-PC compressive strengths

is much wider. For the Cement TI blends, all CKD-PC blends at one day were below

95% of the control cement. At all of the other ages, some blends are above and some

below the 95% threshold. At 90 days, the CKD-PC blends with Cement TI were only

marginally below (93 – 94%) or exceeded the 95% threshold for PC alone compressive

strength. For the Cement TII CKD blends, some blends are above and some below the

95% threshold at all ages.

The compressive strengths for Cement TI with LS at 10% and 20% replacement were

within the compressive strength range of the CKD-PC blends at equal levels of

replacement at all ages. At early ages (one and three days), the Cement TI SLX blend

compressive strengths were also within the range of the Cement TI CKD blends at equal

220

levels of replacement. At later ages (28 and 90 days), however, the Cement TI SLX blend

compressive strengths were lower than the range of the Cement TI CKD blend

compressive strengths at equal levels of replacement.

10.0

15.0

20.0

25.0

30.0

35.0

40.0

45.0

50.0

1 day 3 day 7 day 28 day 90 day

C u rin g T im e

Co

mp

res

siv

e S

tre

ng

th (

MP

a)

TI

TI L S 10%

TI S L X 10%

TI C K D A 10%

TI C K D B 10%

TI C K D C 10%

TI C K D D 10%

TI C K D E 10%

TI C K D F 10%

(a)

10.0

15.0

20.0

25.0

30.0

35.0

40.0

45.0

50.0


C u rin g T im e

Co

mp

res

siv

e S

tre

ng

th (

MP

a)

TI

TI L S 20%

TI S L X 20%

TI C K D A 20%

TI C K D B 20%

TI C K D C 20%

TI C K D D 20%

TI C K D E 20%

TI C K D F 20%

(b)

Figure 4.30 Mortar compressive strength of Cement TI blends at 1, 3, 7, 28, and 90 days

(w/b = 0.485) for (a) 10% replacement and (b) 20% replacement (w/b = 0.485)

221


10.0

15.0

20.0

25.0

30.0

35.0

40.0

45.0


C u rin g T im e

Co

mp

res

siv

e S

tre

ng

th (

MP

a)

TII

TII L S 10%

TII S L X 10%

TII C K D A 10%

TII C K D B 10%

TII C K D C 10%

TII C K D D 10%

TII C K D E 10%

TII C K D F 10%

(a)

10.0

15.0

20.0

25.0

30.0

35.0

40.0

45.0


C u rin g T im e

Co

mp

res

siv

e S

tre

ng

th (

MP

a)

TII

TII L S 20%

TII S L X 20%

TII C K D A 20%

TII C K D B 20%

TII C K D C 20%

TII C K D D 20%

TII C K D E 20%

TII C K D F 20%

(b)

Figure 4.31 Mortar compressive strength of Cement TI blends at 1, 3, 7, 28, and 90 days

(w/b = 0.485) for (a) 10% replacement and (b) 20% replacement (w/b = 0.485)


222

Table 4.13 Compressive strength range for CKD-PC blends as percent of PC alone

TI with 10%

CKD

replacement

TII with 10%

CKD

replacement

TI with 20%

CKD

replacement

TII with 20%

CKD

replacement

1 day 73 – 112% 93 – 109% 65 – 99% 78 – 102%

3 day 96 – 110% 94 – 106% 71 – 100% 71 – 96%

7 day 104 – 113% 94 – 108% 77 – 107% 74 – 103%

28 day 101 – 114% 93 – 104% 90 – 100% 84 – 102%

90 day 99 – 115%

97 – 100% 94 – 114% 89 – 96%

1. Bold: all CKD-PC blends greater than or equal to 95% f’c of PC alone

2. Regular: at least one CKD-PC blend within 90 to 95% f’c of PC alone 3. Italics: at least one CKD-PC blend less than 90% f’c of PC alone

Table 4.14 Compressive strength range for PC-filler blends as percent of PC alone

TI with 10%

filler

replacement

TII with 10%

filler

replacement

TI with 20%

filler

replacement

TII with

20% filler

replacement

LS SLX LS SLX LS SLX LS SLX

1 day 93% 96% 93% 88% 78% 83% 80% 80%

3 day 103% 95% 95% 87% 89% 83% 81% 81%

7 day 105% 98% 104% 85% 94% 88% 89% 72%

28 day 103% 97% 97% 83% 92% 88% 82% 74%

90 day 110% 97% 97% 83% 94% 87% 82% 73%

1. Bold: all PC-filler blends greater than or equal to 95% f’c of PC alone

2. Regular: at least one PC-filler blend within 90 to 95% f’c of PC alone 3. Italics: at least one CKD-PC blend less than 90% of f’c of PC alone

223

The compressive strengths for Cement TII with LS at 10% and 20% replacement were

within the compressive strength range of the Cement TII CKD blends at equal levels of

replacement at all ages. The compressive strengths for Cement TII with SLX at 10%

replacement, however, were lower than the compressive strength range of the Cement TII

CKD blends at equal levels of replacement. At one and three days, Cement TII with SLX

at 20% replacement was within the compressive strength range of the Cement TII CKD

blends. At 7, 28, and 90 days, however, Cement TII with SLX at 20% replacement

compressive strengths was lower than the compressive strength range of the Cement TII

CKD blends at equal levels of replacement.

The CKD-PC blends that had higher strengths at one day generally decreased at 7, 28 and

90 days compared to PC alone. Conversely, the CKD-PC blends that had lower strengths

at one day generally increased at 7, 28, and 90 days compared to PC alone. Generally

speaking, the CKD-PC blends had comparable compressive strengths to PC-LS blends

and higher compressive strengths than PC-SLX blends at equal levels of replacement.

Cement TI CKD blends at one and three day compressive strength have a linear

relationship with a negative slope as a function of the binder SO3 content, as shown in

Figure 4.32. The only known sulfate form to have this effect on PC compressive strength

is calcium sulfate in the form of gypsum. As discussed in Section 2.4.6, the observed

optimum sulfate content in the strength curve implies that the addition of gypsum

involves two opposing effects. The first, which predominates in the lower range of SO3

content, has a beneficial effect on strength. The second, which predominates in the range

of SO3 greater than the optimum, has an adverse effect on compressive strength. This

results in a bell-curve relationship for compressive strength as a function of SO3 content.

The heat of hydration analysis shows that Cement TI has normal sulfate levels to control

aluminate hydration. Therefore, it is expected that excess calcium and sulfate ions

provided by the CKD fraction of the binder will contribute to adverse effects on one day

strengths.

224

10

15

20

25

30

Mo

rta

r C

om

pre

ssiv

e

Str

en

gth

@ 1

da

y,

MP

a

4 4.5 5 5.5 6 6.5 7

SO3, %

(a)

10

15

20

25

30

Mo

rta

r C

om

pre

ssiv

e

Str

en

gth

@ 3

da

y,

MP

a

4 4.5 5 5.5 6 6.5 7

SO3, %

(b)

Figure 4.32 Mortar compressive strength as a function of total sulfate content for Cement

TI CKD blends at (a) 1 day and (b) 3 days (w/b = 0.485)

r = -0.900

10%

20%

Control

PC Replacement

10%

20%

Control

PC Replacement

r = -0.830

225

The one and three day strength relationship with SO3 content for the Cement TII CKD

blends also support the finding that CKD can behave in a similar manner to gypsum

during early-age hydration, as shown in Figure 4.33. From the heat of hydration analysis,

the main hydration and sulfate depletion peaks overlap (occur simultaneously) indicating

that insufficient calcium and sulfate ions were available to control aluminate hydration.

As the sulfate content of the Cement TII CKD blends increased, the one day strength

initially increased but then assumed a negative linear slope. Therefore, the data points

suggest a bell curve very similar to that seen with the addition of calcium sulfate in the

form of gypsum (see Figure 2.7). Two commonly suggested mechanisms of excessive

sulfates are: (i) excessive AFt formation and (ii) accelerated hydration of alite but lower

C-S-H intrinsic strength due to incorporation of SO3 into its structure. Gartner et al.,

(2002) have stated that both mechanisms may contribute to the phenomenon caused by

excessive calcium sulfate. Cement TII has low aluminate content. Therefore, the linear

negative slope relationship as a function of increasing sulfate content for the Cement TII

CKD blends is most likely due to affects on C-S-H, rather than AFt formation at one day

strength.

The effect of increased alkali content is widely reported to increase early strengths and

reduce later strengths. This effect is significantly diminished, however, as the gypsum

content exceeds the optimum sulfate level. Since the presence of CKD appears to

increase the amount of calcium and sulfate ions in solution during early age hydration, it

is not surprising that the effect of alkalis from CKDs does not appear to impact early age

compressive strength. In the absence of high CKD sulfate content, other contributing

factors may govern effects on early age strength. For example, CKD A (low sulfate and

high chloride contents) increased early age strengths, likely due to the accelerating effect

of chlorides.

226

(a)

(b)

Figure 4.33 Mortar compressive strength as a function of total sulfate content for Cement

TII CKD blends at (a) 1 day and (b) 3 days (w/b = 0.485)

Note: Straight line is a linear best fit. Curve is a polynomial best fit.

r = -0.867 (linear fit)

10%

20%

Control

PC Replacement

r = -0.798 (linear fit)

10%

20%

Control

PC Replacement

227

The Cement TI CKD blend 28 day compressive strengths as a function of the percentage

of material passing 45 µm sieve is shown in Figure 4.34. Cement TI CKD blend 28 day

strengths had a linear relationship with a negative slope as a function of percentage

passing the 45 µm sieve. The Cement TI CKD blend 28 day compressive strengths as a

function of the calcium carbonate content are shown in Figure 4.33. Cement TII CKD

blends had a linear relationship with a negative slope as a function of calcium carbonate

content. As discussed previously for the calcite filler, calcium carbonate as a partial

replacement of low C3A cements acts as a diluent. The CKD contribution of calcium

carbonate likely reacts with the aluminate hydrates in Cement TI, whereas Cement TII

has much lower aluminate hydrate content. Scatter in the data for the relationships at 28

day compressive strengths indicates that other factors also influence CKD-PC blend

strength at this age.

A linear relationship for 7 day and 90 day strengths was not evident for the CKD-PC

blends. It is likely a combination of contributing factors that influence the strength

development of CKD-PC blends at these ages.

228

30

32

34

36

38

40

42

Mo

rta

r C

om

pre

ssiv

e

Str

en

gth

@ 2

8 d

ay,

MP

a

88 90 92 94 96

45µm, % Passing

Figure 4.34 Mortar compressive strength at 28 days as a function of percentage passing

45 µm for Cement TI CKD blends

30

32

34

36

38

40

42

Mo

rta

r C

om

pre

ssiv

e

Str

en

gth

@ 2

8 d

ay,

MP

a

0 2.5 5 7.5 10 12.5

Calcite, %

Figure 4.35 Mortar compressive strength at 28 days as a function of calcite for Cement

TII CKD blends (w/b = 0.485)

r = 0.652

10%

20%

Control

PC Replacement

r = -0.789

10%

20%

Control

PC Replacement

229


4.xlii The compressive strength measurements for all Cement TI blends with 10%

CKD replacement were higher than 95% of the PC mortar control, with the

exception of only one blend at the age of one day. All of the compressive

strength measurements for Cement TII blends with 10% CKD replacement

were higher than 93% of the mortar plain control. Many of the CKD-PC

blends compressive strengths were 5 – 15% higher than that of the

respective control PC.

4.xliii All blends made with 10% CKD showed higher strengths at all ages

compared to the blends made with the same CKD at 20%. Therefore, the

replacement level is a factor to consider for the compressive strength effect

for a particular CKD. Some of the blends with CKDs at 20% replacement,

however, performed better than other CKDs at 10% replacement of PC. For

example, CKD A at 20% replacement of Cement TI had higher one day

compressive strength than CKDs B, C, D, and E at 10% replacement of

Cement TI. This is likely due to the high chloride and low sulfate contents

of CKD A. Consequently, the effect on the compressive strength of different

CKDs is related to the composition of the CKD-PC blend as well as the

replacement level.

4.xliv The blends with CKDs D, E, and F had low early compressive strengths but

at later ages had compressive strengths comparable to the PC mixes.

Excessive calcium sulfate in the form of gypsum is known to have this

effect on compressive strength development. Therefore, the sulfate from

CKDs D, E, and F is likely the reason for the lower early strengths and

higher late strengths.

230

4.xlv The CKD-PC blends compressive strengths were comparable to that of PC-

LS blends and higher than PC-SLX blends at both 10% and 20%.

4.xlvi The early age compressive strength is governed by the presence of soluble

calcium and sulfate. The one and three day compressive strength of the

Cement TI CKD blends each have a linear relationship with a negative slope

as a function of the binder SO3 content. The one and three day compressive

strength of the Cement TII CKD blends each appear to have a bell-curve

relationship as a function of the binder SO3 content. It seems the sulfate

content of CKD has a similar impact to the sulfate from gypsum (calcium

sulfate).

4.xlvii In the absence of high CKD sulfate content (CKD sulfate content ≤ PC

sulfate content), chlorides from CKDs increase early age strengths.

4.xlviii Cement TI CKD blend 28 day strengths had a linear relationship with a

negative slope as a function of percentage passing 45 µm sieve. Cement TII

CKD blends had a linear relationship with a negative slope as a function of

calcium carbonate content. The CKD contribution of calcium carbonate

likely binds with the aluminate hydrates in Cement TI, whereas Cement TII

has much lower aluminate hydrate content.

4.2.3 Volume Stability and Durability

4.2.3.1 Expansion in Limewater

The expansion in limewater test (ASTM C1038) is typically used to assess the stability of

mortars due to the presence of calcium sulfate. The expansions in limewater of all

mortars were determined after 14 days. The expansion for PC alone and for blends with

CKD and filler as partial replacements of PC was determined using an average of four

231

mortar specimens. The statistical differences among the mixes were assessed using one-

way analysis of variance (one-way ANOVA) and are presented in Appendix H.

The expansion in limewater for each mortar control and blend is presented in Figure 4.36.

All of the CKD-PC blends had higher expansions than that of the PC alone and filler

blends. The expansion in limewater was similar or higher as the percentage of CKD

replacement increased from 10% to 20%. As the percentage of LS and SLX in the blends

increased from 10% to 20% the expansions were similar. All blends with fillers had

essentially the same levels of expansion (0.003 to 0.008%).

The allowable limit of mortar expansion in limewater is 0.020% for CSA A3001, ASTM

C150, and ASTM C1157. CKDs A, B, and C were below the 0.020% threshold at both

10% and 20% replacement levels of Cement TI and TII. At 10% replacement, CKD D

with both Cements TI and TII and CKD E with Cement TI were higher than 0.020%. At

20% replacement, CKDs D, E, and F with Cements TI and TII were higher than 0.020%.

It is important to note that some of the blends with CKD replacement at 20% had much

lower expansion than blends with 10% replacement, for the same control cement.

The expansion is most significantly correlated to sulfate content in both Cement TI CKD

and Cement TII CKD blends, as shown in Figure 4.37. The expansion in limewater of

CKD-PC blends after 14 days as a function of binder sulfate content is a positive linear

slope. The expansion in limewater is mostly due to the formation of AFt in the hardened

paste. AFt formation requires the presence of C3A. CKD blends with Cement TI had

higher expansions than blends with Cement TII. This can be explained by the higher

levels of C3A in Cement TI than in Cement TII. Scatter in the data implies there could be

factors other than sulfate content that contribute to expansion in limewater.

The linear slope for the Cement TI CKD blends in Figure 4.37(a) indicates that the

expansion in limewater exceeds 0.020% at a sulfate content of approximately 4.75%.

232

Therefore, since the Cement TI sulfate content at 4.35% is optimized according to the

heat of hydration analysis (see Section 4.2.1.1), the expansion in limewater exceeds the

0.020% limit when the Cement TI CKD blend sulfate content is approximately 0.40%

above the optimum Cement TI sulfate content. The linear slope for the Cement TII CKD

blends in Figure 4.37(b) indicates that the expansion in limewater exceeds 0.020% at a

sulfate content of approximately 3.75%. The Cement TII sulfate content at 2.98% is

under-sulfated according to the heat of hydration analysis (see Section 4.2.1.1). The

CKD-PC expansion in limewater exceeds the 0.020% limit when the Cement TII CKD

blend sulfate content is approximately 0.75% above the Cement TII sulfate content.

233

0.00

0.02

0.04

0.06

0.08

0.10

0.12

0.14


Ex

pa

ns

ion

in

Lim

ew

ate

r (%

)

TI

TI L S

TI S L X

TI C K D A

TI C K D B

TI C K D C

TI C K D D

TI C K D E

TI C K D F

(a)

0.00

0.02

0.04

0.06

0.08

0.10

0.12

0.14


Ex

pa

ns

ion

in

Lim

ew

ate

r (%

)

TII

TII L S

TII S L X

TII C K D A

TII C K D B

TII C K D C

TII C K D D

TII C K D E

TII C K D F

(b)

Figure 4.36 Expansion in limewater after 14 days for (a) Cement TI blends and (b)

Cement TII blends


A B C

D E F

A B C

D E

F

A B C

D

E

F A

B C

D

E

F

TI SLX LS TI SLX LS

TII SLX LS TII SLX LS

234

0

0.02

0.04

0.06

0.08

0.1

0.12

0.14

Exp

an

sio

n in

Lim

ew

ate

r, %

4 4.5 5 5.5 6 6.5 7

SO3, %

(a)

0

0.02

0.04

0.06

0.08

0.1

0.12

0.14

Exp

an

sio

n in

Lim

ew

ate

r, %

2.5 3 3.5 4 4.5 5 5.5 6

SO3, %

(b)

Figure 4.37 Expansion in limewater at 14 days as a function of sulfate content for (a)

Cement TI CKD blends and (b) Cement TII CKD blends

r = 0.936

10%

20%

Control

PC Replacement

r = 0.870

10%

20%

Control

PC Replacement

TI CKD D 10% and 20% TI CKD E 10% and 20% TI CKD F 20%

TII CKD D 20% TII CKD E 20% TII CKD F 20%

ASTM maximum limit

ASTM maximum limit

235


4.xlix At 10% CKD replacement of Cement TI the expansions in limewater were 35

– 765% higher than the expansion in limewater of Cement TI. At 20% CKD

replacement of Cement TI the expansions in limewater were 115 – 2400%

higher than the expansion in limewater of Cement TI. At 10% CKD

replacement of Cement TII the expansions in limewater were 110 – 314%

higher than the expansion in limewater of Cement TII. At 20% CKD

replacement of Cement TII the expansions in limewater were 133 – 914%

higher than the expansion in limewater of Cement TII.

4.l Blends with CKDs A, B, and C gave expansions in limewater below the

ASTM C1038 maximum limit of expansion at both 10 and 20% replacement

of Cements TI and TII. Blends with CKDs D, E, and F, however, exceeded

the 0.020% limit. This is due to the significantly higher sulfate contents of

CKDs D, E, and F in comparison to CKDs A, B, and C. It appears that the

amount of CKD replacement of a PC is limited by the CKD-PC sulfate

content, which is to be less than approximately 0.40% above the optimum

sulfate content of the PC.

4.li Some blends with 20% CKD replacement had less expansion in limewater

after 14 days than other blends with 10% CKD replacement. This indicates

that the composition of the CKD-PC blend is more of a governing factor for

expansion in limewater than the level of PC replacement with CKD.

4.lii Expansion of CKD-PC mortars in limewater after 14 days as a function of

binder sulfate content is a positive linear slope. It is hypothesized that the

CKDs contribute excess calcium and sulfate ions to form higher amounts of

AFt than the control PC alone.

236

4.liii Cement TII CKD blends had less expansion in limewater after 14 days than

the Cement TI CKD blends due to the lower aluminate content in Cement TII,

in comparison to Cement TI.

4.2.3.2 Autoclave Expansion

Soundness is the ability of hardened cement paste to retain volume after setting.

Soundness issues generally result from the delayed or slow hydration of magnesium

oxide (MgO) and/or calcium oxide (CaO free lime). It is essential that cement paste, once

it has set, does not undergo a large change in volume; in particular there must be no

appreciable expansion, which, under condition of restraint, could result in a disruption of

the hardened cement paste.

The amount of CKD and filler in each paste was fixed at 10% and 20% by mass of PC,

with a w/b ratio that varied to maintain normal consistency. To assess the repeatability of

the autoclave expansion tests, repeat samples for each control PC were performed, as

shown in Table 4.15. This provides an indication for the level of repeatability to be

expected in the results of the autoclave expansion for all tests.

Table 4.15 Autoclave expansions for (a) Cement TI and (b) Cement TII

(a)

PC Autoclave

Expansion (%)

TI 0.040

TI 0.042

TI 0.038

TI 0.035

(b)

PC Autoclave

Expansion (%)

TII 0.055

TII 0.057

237

The autoclave expansion for each paste control and blend is presented in Figure 4.38. All

of the CKD-PC blends had similar or higher expansion than that of the PC alone or the

filler blends. The blends with filler materials had marginally lower expansions than PC

alone. The autoclave expansion was similar or higher than the percentage of CKD

replacement increased from 10% to 20%. As the percentage of LS and SLX in the blends

increased from 10% and 20%, the expansions decreased. Some blends with 20% CKD

replacement had less autoclave expansion than other blends with 10% CKD replacement.

This indicates that the composition of the CKD-PC blend is more of a governing factor

for autoclave expansion than the level of PC replacement with CKD.

The ranges for autoclave expansions of the CKD-PC blends are shown in Table 4.16. The

free lime contents of the CKD-PC blends are higher than PC alone. Since the free lime

contents of CKD-PC blends vary significantly, however, the results were separated into

blends made with high and low free lime CKDs. All of the CKD-PC blends were well

below the ASTM C150 limit of 0.80% and CSA A3001 limit of 1.0%. Therefore, all

CKD-PC blends are acceptable in terms of long-term soundness/durability from the

viewpoint of undesirable autoclave expansion according to ASTM C150.

ASTM C465, the specification for processing additions, however, states that the impact

shall not be more than 0.10% greater than the expansion of the control cement. Blends

with 10% CKD replacement were generally within this range for the two PCs, as required

in ASTM C465. Some blends with 20% CKD replacement were below the 0.10%

expansion of the cement alone, while others were higher. The CKD-PC blends that were

within the 0.10% expansion range of the PC had low free lime contents. Therefore, CKDs

with very high free lime contents may still meet the ASTM C465 requirement for

soundness at 10% replacement of PC.

238

0.00

0.05

0.10

0.15

0.20

0.25

0.30

0.35

0.40


Au

toc

lav

e E

xp

an

sio

n (

%)

TI

TI L S

TI S L X

TI C K D A

TI C K D B

TI C K D C

TI C K D D

TI C K D E

TI C K D F

(a)

0.00

0.05

0.10

0.15

0.20

0.25

0.30

0.35

0.40


Au

toc

lav

e E

xp

an

sio

n (

%)

TII

TII L S

TII S L X

TII C K D A

TII C K D B

TII C K D C

TII C K D D

TII C K D E

TII C K D F

(b)

Figure 4.38 Autoclave Expansions for (a) Cement TI blends and (b) Cement TII blends


C

A

B C

D

E

F

A

B

C

D

E

F

A B

C

D

E

F A B

C

D

E

F

TI

SLX LS

TI

SLX LS

TII

SLX LS

TII

SLX

LS

239

Table 4.16 Range of autoclave expansions for all blends

Cement Type CKD

Replacement

CKDs A, B, C,

(low free lime content)

Expansion Change (%)

CKDs D, E, F

(high free lime content)

Expansion Change (%)

10% -0.009 to 0.021 0.024 to 0.091 Cement TI

20% 0.003 to 0.037 0.057 to 0.192

10% 0.016 to 0.051 0.026 to 0.112 Cement TII

20% 0.029 to 0.105 0.083 to 0.325

Bold: At least 1 sample is greater than 0.10% than the control PC

The autoclave expansion is most significantly correlated to free lime content for both

Cement TI CKD and Cement TII CKD blends, as shown in Figure 4.39. The autoclave

expansion of CKD-PC blends as a function of binder free lime content is a positive linear

slope. The expansion is mostly due to the formation of calcium hydroxide in the hardened

paste. It should be noted that CKD-PC blends with CKD F were excluded from the

regression analysis, but the data points are still shown (encircled) in Figure 4.39.

Although CKD F had the highest free lime, it did not have the highest expansion.

Soundness cannot always be predicted reliably from free lime content of a CKD-PC

blend, since its hydration reactivity is a function of its decarbonation temperature. CKD F

is from a preheater/precalciner pyroprocess which calcinates CKDs at a lower

temperature than that of wet and long-dry kiln CKDs. Free lime that has been

decarbonated at low temperatures readily reacts with water in the plastic paste (see Figure

2.9) and, therefore, does not contribute to autoclave expansion in the hardened paste. The

excessive heat evolution during initial hydrolysis, increased water demand, and decreased

flow of blends with CKD F all indicated that the free lime content was very reactive, as is

expected for a CKD from a preheater/precalciner.

Scatter in the data implies there could be other factors than free lime content that

contribute to autoclave expansion, such as reactivity of free lime (as discussed above).

240

0

0.1

0.2

0.3

0.4

Au

tocla

ve

Exp

an

sio

n,

%

0 2 4 6 8

Free CaO, %

(a)

0

0.1

0.2

0.3

0.4

Au

tocla

ve

Exp

an

sio

n,

%

0 2 4 6 8

Free CaO, %

(b)

Figure 4.39 Autoclave expansion as a function of free lime content (excluding data points

in the circles) for (a) Cement TI CKD blends and (b) Cement TII CKD blends

r = 0.975

10%

20%

Control

PC Replacement

r = 0.938

10%

20%

Control

PC Replacement

CKD F

blends

CKD F

blends

241


4.liv At 10% CKD replacement of Cement TI the autoclave expansions were

between 22% lower and 228% higher than the autoclave expansion of Cement

TI. At 20% CKD replacement of Cement TI the autoclave expansions were 7-

480% higher than the autoclave expansion of Cement TI. At 10% CKD

replacement of Cement TII the autoclave expansions were 29-191% higher

than the autoclave expansion of Cement TII. At 20% CKD replacement of

Cement TII the autoclave expansions were 47-591% higher than the autoclave

expansion of Cement TII.

4.lv The CKD-PC blends had similar or higher autoclave expansions than PC

alone, but all were well below the ASTM C150 specification of 0.80%. PC-

filler blends had slightly lower autoclave expansion levels than PC alone.

4.lvi Some blends with 20% CKD replacement had less autoclave expansion than

other blends with 10% CKD replacement. This indicates that the composition

of the CKD-PC blend is more of a governing factor for autoclave expansion

than the level of PC replacement with CKD.

4.lvii Blends with 10% CKD replacement were typically within 0.10% expansion of

the two PC controls, as required in ASTM C465. Some blends with 20%

replacement CKD were below the 0.10% expansion of the cement alone,

while others were higher. The CKD-PC blends that were similar or below

0.10% expansion of the PC alone had low free limes (< ~ 4%).

4.lviii Expansion of CKD-PC pastes in the autoclave expansion as a function of free

calcium oxide binder content has a positive linear slope. It is hypothesized

that the CKDs contribute hard burnt free lime that hydrates to form higher

242

amounts of calcium hydroxide than from the control PC alone. The expansion

of hydrating lime is caused by crystallization of Ca(OH)2. Scatter in the linear

relationship with free lime content indicates that other factors may contribute

to unsoundness, such as the reactivity of the free lime.

4.lix Soundness cannot always be predicted reliably from the free lime content of a

CKD-PC blend since its hydration reactivity is a function of its decarbonation

temperature. Free lime that has been decarbonated at low temperatures readily

reacts with water in the plastic paste and therefore does not contribute to

expansion in the hardened paste.

4.2.3.3 Alkali Silica Reactivity

This program was designed to develop an understanding of the effects of CKD and is not

aimed at addressing the ASR mitigation of mixes incorporating CKDs. The objective was

to determine the influence of different types of CKD on ASR expansion tests. One of the

concerns with the CSA A23.2-14A ASR test for expansion is that the NaOH is used to

offset the sodium equivalent alkali (Na2Oe) level to a constant value of 5.25 kg/m3. This

study attempts to assess the impact of CKDs on CSA A23.2-14A concrete prism

expansions.

The details of the concrete mixes within the two test series are shown in Table 4.17. For

Test Series I, CKD replacement was constant at 10% of Cement TI and the amount of

NaOH addition varied to attain the desired Na2Oe loading of 5.25 kg/m3 in concrete

(based on the alkali content of both the PC and CKD). For Test Series II, the NaOH

addition was kept constant for the CKD-PC blends but the amount of CKD replacement

varied. Due to its lower alkali content, the TII series of blends required much more

NaOH addition to bring the alkali loading of each blend to 5.25 kg/m3 than the TI series

of blends .

243

Table 4.17 ASR concrete mix alkali loadings and CKD replacement levels for (a) Test

Series I: Cement TI CKD blends and (b) Test Series II: Cement TII CKD blends

(a)

Cement TI Blends Na2Oe loading in binder

(%)

Binder

(kg/m3)

NaOH

(kg/m3)

Expansions (%)

1 year 2 years

Cement TI - CTL 1 1.25 420 1.518 0.130 0.193

CKD A 10% 1.25 420 0.542 0.174 0.262

CKD B 10% 1.25 420 0.054 0.146 0.248

CKD C 10% 1.25 420 0.813 0.157 0.224

CKD D 10% 1.25 420 0.651 0.167 0.224

CKD E 10% 1.25 420 0.163 0.174 0.258

CKD F 10% 1.25 420 0.542 0.163 0.257

Cement TI - CTL 2 1.38 378 2.013 0.142 0.202

All blends had 5.25 kg/m3 of Na2Oe in concrete mix

(b)

Cement TII Blends Na2Oe loading in binder

(%)

Binder

(kg/m3)

NaOH

(kg/m3)

Expansions (%)

1 year 2 years

Cement TII - CTL 1 1.25 420 3.633 0.182 0.262

CKD A 9.8% 1.25 420 2.452 0.173 0.227

CKD B 7.0% 1.25 420 2.452 0.189 0.253

CKD C 12.9% 1.25 420 2.452 0.175 0.240

CKD D 10.9% 1.25 420 2.452 0.197 0.258

CKD E 7.7% 1.25 420 2.452 0.213 0.297

CKD F 10.1% 1.25 420 2.452 0.191 0.247

Cement TII - CTL 2 1.03 420 2.452 0.149 0.211

All blends had 5.25 kg/m3 of Na2Oe in concrete mix except Cement TII CTL 2 which had 4.34 kg/m3.

244

The ASR expansion tests for Test Series I and II are shown in Figure 4.40. For Test

Series I, the CKD-PC blends had higher expansions after two years in comparison to both

of the controls with PC alone. This implies that either (i) the alkali contribution from

CKDs causes more ASR expansion than the contribution of alkalis from NaOH addition,

or (ii) there are factors other than ASR that cause expansion to occur. It is reasonable to

assume that expansions due to high sulfate and free lime contents found in CKDs

contribute to expansion during the ASR test. A series of tests using two cement types

indicates that CKD can have a pronounced effect on ASR expansion tests, but it is

dependent on factors other than alkali level.

For Test Series II, the CKD-PC blends had similar or lower expansions after two years in

comparison to Cement TII CTL 1, with the exception of the blend with 7.7% CKD E.

The ASR expansion results in the Test TII series indicate that for an equivalent alkali

loading, NaOH is more reactive than Cement TII alkalis but less reactive than the alkalis

in CKDs or other CKD factors.


4.lx CKDs can increase the expansion in the CSA A23.2-14A ASR concrete prism

test. This effect, however, is likely dependent on factors other than alkali

level. High sulfate and free lime contents can also influence the amount of

expansion during the ASR test.

245

(a)

(b)

Figure 4.40 ASR expansions over 2 years for (a) Test Series I: Cement TI CKD blends

and (b) Test Series II: Cement TII CKD blends

246

5.0 MAIN CONTRIBUTIONS OF THE THESIS

5.1 CKD Characterization

Studies have shown that CKDs can be interground or blended as a partial substitute of PC

between 5% and 15%, by mass. Although the use of CKDs is promising, there is very

little understanding of their effects on concrete. Previous studies provide variable and

often conflicting results. The reasons for the inconsistent results are not obvious due to

the lack of compositional data provided in the literature. It was also found that

compositional analysis procedures designed for PC are sometimes inappropriate to

determine the characteristics of CKDs. The characteristics of a CKD must be well-

defined in order to understand its potential impact in concrete.

A wide range of CKDs from different kiln processes were studied to assess overall CKD

characterization. Within the range of materials used in this study, the following main

contributions towards CKD characterization are:

1. The present study identifies the appropriate chemical and physical analytical

methods that should be used for accurate CKD composition analysis. CKDs must

be prepared and analyzed differently from PCs for accurate chemical and physical

analysis. This will assist other researchers and the industry in properly

characterizing their CKDs in future.

2. A greater understanding of the fineness properties of CKDs has resulted from this

investigation. Due to the lack of a size selection process, CKDs have a broader

particle size range than PCs. Also, the Blaine fineness of a CKD is largely

representative of the percentage of particles of less than 10 µm while the

percentage passing the 45 µm sieve is more representative of the percentage of

particles between 10 and 100 µm. This will help researchers correctly interpret the

fineness test results typically used for CKDs.

247

3. A process flow diagram to determine the relative abundance of the different

phases within CKDs was introduced. The characteristics of CKDs are

traditionally evaluated based on chemical analysis data. Such data does not,

however, indicate the ways in which the different elements actually exist within

the CKD and how they might be expected to react during hydration. Alkalis, for

example, may occur as separate crystalline phases in the form of alkali chlorides

or alkali sulfates. The reactivity of elements may therefore be expected to vary,

depending on the form in which they actually exist.

4. CKDs consist of clinker phases, calcium carbonate, quartz, clays, free lime,

portlandite, periclase, alkali chlorides, alkali sulfates, anhydrite, calcium

langbeinite, fly ash, and/or slag. Some of the phases identified in the CKDs had

not been previously recognized in the literature (i.e., calcium langbeinite) and can

influence hydration significantly.

5. The initial dissolution of ionic species in water and the composition of the liquid

phase play an important role in PC hydration. The availability of ions during the

initial minutes of hydration was used to assess the differences in reactivity

between various types of CKDs and PC. CKDs generally provide the same ions as

PC during initial dissolution, except some CKDs may also contribute chloride

ions. Calcium chloride, however, is commonly used as an accelerator in non-

reinforced concrete in cold weather. Other than the impact of chlorides, this

implies that CKD-PC blends could perform in similar manner to PC alone.

248

5.2 CKD-PC Blends

CKDs contain various components that affect performance and durability properties

when used as a partial replacement of PC. The chemical, physical, and mineralogical

properties of CKDs vary considerably between different cement plants and even within

the same plant. Therefore, it has been difficult to separate the effects of individual CKD

components on CKD-PC blends. Although the single effect of any one of the common

components found in CKDs can be stated in general terms, specific reactions among

more than one component are sometimes difficult to predict. Improved understanding of

the CKD-PC interaction will allow for optimization and increased utilization of these

blends in concrete.

The majority of previous CKD-PC research has generally used only one or two CKDs

and one PC (Table 2.10). Since CKDs and PCs can vary considerably, it is very difficult

to make conclusions on CKD-PC interaction based upon only one or two types of CKD

and one PC. The current study utilized seven CKDs with a wide range of composition

characteristics, two fillers, and two PCs. Within the range of materials and CKD and

filler replacement levels investigated in this study, the following main contributions

towards the performance of CKD-PC blends are:

1. CKD-PC blends can show comparable performance properties to PC alone and to

PC-filler blends. The components that govern the effects of CKDs as partial

replacement of PCs are: free lime, sulfates, chlorides, alkalis, calcium carbonate,

and fineness.

2. The most significant contribution to the optimization of CKD-PC blends is the

new premise that CKDs can contribute calcium and sulfate ions that are readily

available to control aluminate hydration. Many of the adverse effects of CKD-PC

blends are related to excessive amounts of calcium and sulfate ions. Therefore, if

249

CKD is used as partial PC replacement, optimum SO3 should be determined for

the CKD-PC blend and that would likely lead to lower gypsum additions.

3. The results of this study have been used to present the effects and relationships of

individual CKD-PC blend components using regression analysis techniques. The

effects and relationships based upon compositional analysis of the CKD-PC

blends are:

i. Water demand for pastes is higher for CKD-PC blends than for PC

alone. Very high and reactive amounts of free lime significantly increase

water demand. In the absence of high and reactive amounts of free lime,

the water demand of CKD-PC blends was similar or higher than the PC

alone.

ii. Mortar flow is generally lower for CKD-PC blends than for PC alone.

Very high and reactive amounts of free lime significantly increase water

demand. In the absence of high and reactive amounts of free lime, it

appears that the particle size distribution influences the flow. CKD-PC

blend flows decreased linearly as the percentage of particles passing 45

µm (Cement TI blends) and 30.5 (Cement TII blends) µm decreased.

iii. CKDs from preheater/precalciner kilns have high amounts of reactive

free lime that cause the impact of water demand and flow to be

significantly different in comparison to CKDs from wet and long-dry

kilns. Therefore, the preheater/precalciner kiln CKDs may need to be

categorized separately from wet and long-dry kiln CKDs.

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iv. The presence of CKDs generally delays hydration of C3S in CKD-PC

blends. The data suggests the magnitude of this delay is linearly related

to the increased concentration of alkalis in the CKD-PC blends.

v. Since normal set is generally accepted to be a result of the onset of C3S

hydration, the presence of alkalis that delay C3S hydration will also

delay normal initial set. However, accelerated initial set may occur due

to the precipitation of hydration products that are not directly related to

C3S hydration (abnormal set). The likely precipitate products are AFt,

syngenite, calcium sulfate, and/or calcium hydroxide.

vi. CKDs influence the strength development of CKD-PC blends and tend

to have low early strengths and higher late age strengths. The increased

sulfate contents (beyond the PC optimum sulfate content) of the CKD-

PC blends reduced early age strengths. In the absence of high CKD

sulfate content, increased chloride content due to CKDs increased early

age strengths. For Cement TI (normal C3A), later age strengths were

adversely affected due to a lower percentage of particles passing the 45

µm sieve. For Cement TII (low C3A), the calcium carbonate fraction of

CKD performed as a diluent and resulted in lower later-age strengths.

vii. CKD-PC blends have higher expanions in limewater than PC alone.

Increased expansions in limewater of CKD-PC blends are linearly

related to increased concentrations of sulfate in the binder, likely due to

the formation of AFt in the hardened paste. It is believed that an

optimized sulfate content for a CKD-PC blend would mitigate these

expansions.

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viii. CKD-PC blends have higher autoclave expansions than PC alone.

Increased autoclave expansions are related to high amounts of hard burnt

free lime content as opposed to total free lime content. It appears there

are also other contributing factors to autoclave expansion, such as the

presence of coarser particles in CKDs.

4. This study provides a contribution to the limited data that exists for the impact of

CKD-PC blends on ASR. It appears CKD-PC blends will result in higher ASR

expansion and that mitigative measures may have to be increased from those

currently recommended in CSA A23.2-27A.

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6.0 CONCLUSIONS

Within the range of materials and CKD replacement levels investigated in this study, the

following conclusions are made.

1. CKD compositions vary with kiln process and the raw materials used. Therefore, the

impact of CKD as a partial replacement of PC may not be consistent. Further, a

particular CKD may impact CKD-PC blends differently due to varying compositions

in PC.

2. Thermal and compositional anaylsis methods used for PC must be modified to use on

CKDs by correcting for the volatile compounds that may be released during the LOI

test and fused bead preparation.

3. CKDs may contain significant amounts of amorphous material (>30%) and clinker

compounds (>20%) and small amounts of slag and/or fly ash (<5%) (if used as raw

materials in clinker production) and calcium langbeinite (<5%). Although these

materials/compounds do not necessarily govern the impact of CKD in a CKD-PC

blend, it is important to recognize they can have an influence on hydration and on the

compounds that are formed.

4. CKDs from preheater/precalciners have different effects on workability and heat

evolution than CKDs from the wet and long-dry kilns. The blends with the two CKDs

from preheater/precalciner plants had higher paste water demand, lower mortar flows,

and higher heat generation during initial hydrolysis in comparison to all other blends

and control cements. This is due to the high amounts of reactive free lime (>20%) in

CKDs from preheater/precalciner processes.

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5. The effect of CKD as a partial replacement of PC appears to be governed by the

sulfate content of the CKD-PC blend (however, the form of the CKD sulfate is not

significant). According to the analysis of the ASTM C1038 expansion in limewater

test results in this study, the CKD-PC sulfate content should be less than ~0.40%

above the optimum sulfate content of the PC.

6. CKD in CKD-PC blends behaved similarly to the addition of gypsum to PC.

Therefore, CKD-PC blends could be optimized for sulfate content by using CKD as a

partial substitute of the gypsum during the grinding process to control the early

hydration of C3A. The wet and long-dry kiln CKDs contain significant amounts of

calcium carbonate (>20%) which could also be used as partial replacement of

limestone filler in PC. The impact of additional CKD components would need to be

considered.

7. With the knowledge gained in this thesis and other research studies, there may be

efforts directed towards modifying North American industry standards to allow for

appropriate utilization of CKDs as partial replacement of PC, between 5 and 10% by

mass. These changes would likely require less emphasis on the use of compositional

specifications and greater importance on the use of performance standards such as

ASTM C1157.

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7.0 RECOMMENDATIONS FOR FUTURE WORK

1. The current study provides an understanding of the effect of free calcium and

sulfate ions from CKDs on C3S and C3A hydration in CKD-PC blends. Many of

the adverse effects of CKD-PC blends are related to excessive sulfate contents. It

would be useful to assess performance of the CKD-PC blends at optimum sulfate

content (as a partial substitute of gypsum).

2. The excessive contribution of free calcium and sulfate ions from CKDs appears to

dominate the behaviour of CKD-PC blends. Since gypsum (calcium sulfate) is

known to have a significant impact on drying shrinkage, this is another volume

stability parameter that should be investigated.

3. The two CKDs from preheater/precalciner plants performed significantly

differently in comparison to the CKDs from the wet and long-dry kilns with

respect to influence on water demand and flow. It would be beneficial to conduct

future studies with preheater/precalciner CKDs separate from wet and long-dry

kiln CKDs, particularly at PC replacement levels greater than 10%.

4. The current study utilized dry blending to mix the CKD-PC blends. Intergrinding

the CKD-PC blends, however, may produce different results. For example, it is

important to highlight the potential impact of highly reactive free lime to cause

gypsum false set if CKD from preheater/precalciners is interground with PC, as

opposed to being blended. Free lime, if too high and/or reactive, enhances

gypsum dehydration by its considerable hygroscopity (which allows it to extract

water from gypsum molecules during milling when they are in a state of

perturbation from the heat generated by frictional forces and liable to be subjected

to some decomposition) and also has the effect of delaying rehydration of

hemihydrate (Bensted, 1983b). This could enhance the likelihood of a plaster

255

(gypsum) false set. Therefore, the differences between intergrinding and blending

CKD-PC blends should be investigated.

5. The stirred suspension dissolution analyses of CKDs and PCs at w/b ratio of 10:1

were very useful to gain an understanding of rapid ion dissolution differences

between CKDs and PC during early age hydration. It would be interesting to

conduct further investigations of the actual CKD-PC blend pore solutions with

more practical w/b ratios, such as 0.4 to 0.7 at various ages. It is recommended

that the pore solution extractions be perfomed at very frequent periods during the

early stages of hydration. Geochemical software programming (i.e., PHREEQC)

could also be used to model and predict the hydration products at each stage.

6. The current study provides a hypothesis for the microstructural development of

CKD-PC blends during hydration based upon the effects and relationships among

the binder compositions and their performance in various physical tests. Further

work is needed to investigate the formation of hydration products as well as

morphology changes to C-S-H at various hydration ages.

7. The role of C3A is very important in CKD-PC blends. It would be interesting to

conduct studies on the reactions of C3A in the concomitant presence of calcium

sulfate, calcium chloride, and calcium carbonate. Each of these compounds is

known to react with C3A individually, but how they react together, as in CKDs, is

not yet clearly defined.

8. The hydration, mechanical properties, and durability effects of CKD-PC blends

with SCMs and/or chemical admixtures were not included in this study. This

needs to be investigated further.

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9. The current study shows that CKDs contribute to deleterious ASR expansion

based upon the concrete prism tests. Measures to mitigate ASR expansion of

CKD-PC blends should be investigated, such as the addition of SCMs.

10. There are other durability concerns of CKD-PC blends, besides ASR. Elevated

concentrations of chlorides contribute to steel corrosion in concrete. Excessive

amounts of sulfate can contribute to internal sulfate attack. Higher alkali contents

can impact freezing and thawing resistance. Permeability may also be increased

due to the dilution of PC with CKDs. These durability concerns need to be

assessed.

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268

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269

Appendix A. CKD Chemical Composition Correction Calculations

270

271

Appendix B. PC and CKD TGA Analysis

272

Cement TI

Cement TII

273

CKD A

CKD B

274

CKD C

CKD D*

275

CKD D

CKD E

276

CKD F

277

Appendix C. CKD XRD Scans

278

C

KD

A

279

C

KD

B

280

C

KD

C

281

C

KD

D*

282

C

KD

D

283

C

KD

E

284

C

KD

F

285

Appendix D. PC, CKD-PC, and PC-Filler Properties

286

Table D.1 Chemical and Physical Composition of

TI Blends with 10% Replacement

Components TI TI CKD A

10% TI CKD B

10% TI CKD C

10% TI CKD D

10% TI CKD E

10% TI CKD F

10% TI CKD LS 10%

TI CKD SLX 10%

SiO2 19.15 18.66 19.65 18.67 18.68 18.76 18.92 17.50 27.05

Al2O3 5.83 5.62 6.16 5.65 5.74 5.63 5.64 5.32 5.29

Fe2O3 2.46 2.40 2.59 2.37 2.43 2.44 2.40 2.23 2.22

CaO 62.03 60.26 59.10 60.30 60.38 61.35 61.41 61.18 55.83

MgO 2.18 2.14 2.15 2.07 2.13 2.25 2.27 2.02 1.96

SO3 4.35 4.22 4.49 4.65 5.53 5.09 4.81 3.92 3.92

Na2O 0.30 0.33 0.32 0.29 0.34 0.30 0.30 0.27 0.27

K2O 1.01 1.25 1.39 1.23 1.36 1.39 1.28 0.93 0.92

Na2Oe 0.97 1.15 1.24 1.10 1.23 1.21 1.14 0.89 0.88

Sol. Na2O 0.16 0.18 0.17 0.15 0.18 0.16 0.16 0.14 0.14

Sol. K2O 0.97 1.14 1.26 1.07 1.16 1.26 1.11 0.87 0.87

Sol. Na2Oe 0.80 0.93 1.00 0.86 0.95 0.99 0.89 0.72 0.72

TiO2 0.25 0.26 0.28 0.25 0.25 0.25 0.24 0.23 0.23

P2O5 0.26 0.24 0.24 0.24 0.25 0.24 0.24 0.23 0.23

Mn2O3 0.09 0.09 0.09 0.08 0.09 0.13 0.09 0.08 0.08

Cl 0.00 0.25 0.09 0.04 0.03 0.22 0.08 0.00 0.00

LOI 1.79 4.48 3.39 3.98 2.60 2.19 2.15 5.84 1.63

pH* 11.90 11.92 11.92 11.94 11.95 11.99 11.99 11.66 11.31

Ca(OH)2 0.40 0.36 0.36 0.36 0.36 0.46 0.85 0.36 0.36

fCaO 0.40 0.81 0.76 0.93 1.42 3.20 3.81 0.36 0.36


Blaine (m2/kg) 367 396 399 398 391 365 383 379 394

45µm, % passing 95.74 93.50 92.48 93.28 94.89 93.07 93.66 96.12 95.98

Na2Oe: Na2O + 0.658 (K2O) LOI: Loss on ignition * based on w/b = 10 solution analysis @ 10 minutes fCaO: free lime

287


TI Blends with 20% Replacement


20% TI CKD B

20% TI CKD C

20% TI CKD D

20% TI CKD E

20% TI CKD F

20% TI CKD LS 20%

TI CKD SLX 20%

SiO2 19.15 18.17 20.14 18.18 18.21 18.37 18.68 15.84 34.95

Al2O3 5.83 5.42 6.49 5.47 5.65 5.42 5.45 4.80 4.76

Fe2O3 2.46 2.35 2.72 2.28 2.40 2.42 2.35 2.01 1.98

CaO 62.03 58.49 56.16 58.57 58.73 60.66 60.80 60.32 49.63

MgO 2.18 2.11 2.11 1.95 2.08 2.32 2.36 1.86 1.75

SO3 4.35 4.09 4.64 4.94 6.71 5.83 5.27 3.49 3.49

Na2O 0.30 0.36 0.35 0.28 0.37 0.29 0.30 0.24 0.24

K2O 1.01 1.48 1.77 1.45 1.70 1.78 1.54 0.85 0.83

Na2Oe 0.97 1.33 1.51 1.23 1.49 1.46 1.32 0.80 0.79

Sol. Na2O 0.16 0.20 0.19 0.15 0.21 0.16 0.16 0.13 0.13

Sol. K2O 0.97 1.31 1.55 1.17 1.35 1.56 1.26 0.77 0.77

Sol. Na2Oe 0.80 1.06 1.21 0.92 1.10 1.19 0.98 0.64 0.64

TiO2 0.25 0.28 0.31 0.24 0.25 0.25 0.24 0.21 0.21

P2O5 0.26 0.23 0.23 0.21 0.24 0.23 0.22 0.21 0.21

Mn2O3 0.09 0.08 0.08 0.08 0.09 0.17 0.08 0.07 0.07

Cl 0.00 0.50 0.19 0.08 0.07 0.44 0.17 0.00 0.00

LOI 1.79 7.18 5.00 6.18 3.42 2.60 2.52 9.89 1.47

pH* 11.90 11.94 11.95 11.98 12.00 12.09 12.09 11.42 10.72

Ca(OH)2 0.40 0.32 0.32 0.32 0.32 0.52 1.30 0.32 0.32

fCaO 0.40 1.22 1.13 1.46 2.44 6.01 7.22 0.32 0.32


Blaine (m2/kg) 367.00 424 430 430 416 364 399 391 421

45µm, % passing 95.74 91.25 89.21 90.81 94.04 90.39 91.57 96.50 96.21


288


TII Blends with 10% Replacement

DESCRIPTION TII TII CKD A 10%

TII CKD B 10%

TII CKD C 10%

TII CKD D 10%

TII CKD E 10%

TII CKD F 10%

TII CKD LS 10%

TII CKD SLX 10%

SiO2 20.39 19.77 20.75 19.78 19.79 19.87 20.03 18.61 28.16

Al2O3 4.21 4.16 4.70 4.19 4.28 4.16 4.18 3.85 3.83

Fe2O3 3.01 2.90 3.08 2.86 2.92 2.93 2.90 2.73 2.71

CaO 63.06 61.18 60.02 61.23 61.30 62.27 62.34 62.10 56.75

MgO 3.21 3.07 3.07 2.99 3.06 3.18 3.20 2.95 2.89

SO3 2.98 2.98 3.26 3.41 4.30 3.86 3.58 2.68 2.68

Na2O 0.13 0.18 0.17 0.14 0.18 0.14 0.15 0.12 0.12

K2O 0.69 0.95 1.10 0.94 1.06 1.10 0.98 0.64 0.62

Na2Oe 0.58 0.80 0.89 0.75 0.88 0.87 0.80 0.54 0.53

Sol. Na2O 0.06 0.09 0.09 0.07 0.10 0.07 0.07 0.06 0.06

Sol. K2O 0.64 0.84 0.97 0.78 0.87 0.97 0.82 0.58 0.58

Sol. Na2Oe 0.49 0.65 0.72 0.58 0.67 0.71 0.61 0.44 0.44

TiO2 0.26 0.27 0.29 0.25 0.26 0.26 0.25 0.24 0.24

P2O5 0.12 0.12 0.12 0.11 0.12 0.12 0.12 0.11 0.11

Mn2O3 0.56 0.51 0.51 0.51 0.51 0.55 0.51 0.50 0.50

Cl 0.00 0.25 0.09 0.04 0.03 0.22 0.08 0.00 0.00

LOI 1.28 4.02 2.93 3.52 2.14 1.74 1.70 5.38 1.17

pH* 11.90 11.92 11.92 11.94 11.95 11.99 11.99 11.66 11.31

Ca(OH)2 1.30 1.17 1.17 1.17 1.17 1.27 1.66 1.17 1.17

fCaO 0.55 0.94 0.90 1.06 1.55 3.34 3.94 0.49 0.49


Blaine (m2/kg) 377 405 408 407 400 374 392 388 403

45µm, % passing 92.01 90.14 89.12 89.92 91.53 89.71 90.30 92.76 92.62


289


TII Blends with 20% Replacement


TII CKD B 20%

TII CKD C 20%

TII CKD D 20%

TII CKD E 20%

TII CKD F 20%

TII CKD LS 20%

TII CKD SLX 20%

SiO2 20.39 19.16 21.12 19.17 19.19 19.36 19.67 16.83 35.94

Al2O3 4.21 4.12 5.19 4.17 4.35 4.12 4.15 3.50 3.46

Fe2O3 3.01 2.79 3.16 2.72 2.84 2.86 2.79 2.45 2.42

CaO 63.06 59.31 56.99 59.40 59.55 61.48 61.62 61.14 50.45

MgO 3.21 2.93 2.93 2.77 2.91 3.14 3.19 2.68 2.57

SO3 2.98 2.99 3.54 3.84 5.61 4.73 4.18 2.39 2.39

Na2O 0.13 0.22 0.21 0.14 0.24 0.16 0.17 0.11 0.11

K2O 0.69 1.22 1.51 1.19 1.44 1.51 1.28 0.59 0.56

Na2Oe 0.58 1.02 1.20 0.92 1.18 1.15 1.01 0.50 0.48

Sol. Na2O 0.06 0.13 0.11 0.07 0.13 0.08 0.08 0.05 0.05

Sol. K2O 0.64 1.05 1.29 0.91 1.09 1.30 1.00 0.51 0.51

Sol. Na2Oe 0.49 0.81 0.96 0.67 0.85 0.94 0.73 0.39 0.39

TiO2 0.26 0.29 0.32 0.25 0.26 0.26 0.25 0.21 0.21

P2O5 0.12 0.12 0.12 0.10 0.13 0.12 0.11 0.10 0.10

Mn2O3 0.56 0.46 0.46 0.46 0.46 0.55 0.46 0.45 0.45

Cl 0.00 0.50 0.19 0.08 0.07 0.44 0.17 0.00 0.00

LOI 1.28 6.77 4.59 5.77 3.01 2.20 2.12 9.48 1.06

pH* 11.90 11.94 11.95 11.98 12.00 12.09 12.09 11.42 10.72

Ca(OH)2 1.30 1.04 1.04 1.04 1.04 1.24 2.02 1.04 1.04

fCaO 0.55 1.34 1.24 1.58 2.55 6.13 7.34 0.44 0.44


Blaine (m2/kg) 377 432 438 438 424 372 407 399 429

45µm, % passing 92.01 88.27 86.23 87.83 91.05 87.41 88.59 93.52 93.23


290

Table D.5 Mineralogical Composition of TI Blends with 10% Replacement


10% TI CKD B

10% TI CKD C

10% TI CKD D

10% TI CKD E

10% TI CKD F

10% TI CKD LS 10%

TI CKD SLX 10%

Alite 68.60 61.86 61.74 61.84 61.89 61.92 61.83 61.74 61.74

ß-Belite 10.30 11.46 10.04 10.32 9.87 10.62 9.66 9.27 9.27

Aluminate 8.70 7.88 7.88 7.90 7.88 7.97 7.88 7.83 7.83

Brownmillerite 7.50 6.77 6.81 6.81 6.75 6.99 6.80 6.75 6.75

Gypsum 1.70 1.53 1.53 1.53 1.53 1.53 1.53 1.53 1.53

Hemihydrate 0.50 0.45 0.45 0.45 0.45 0.45 0.45 0.45 0.45

Calcite 0.70 5.89 4.10 5.76 2.90 0.75 1.05 10.43 0.82

Quartz 0.30 1.19 0.99 1.35 0.59 0.92 0.87 0.47 10.09

Dolomite 0.00 0.45 0.31 0.00 0.10 0.00 0.00 0.00 0.00

Periclase 1.40 1.32 1.33 1.27 1.29 1.47 1.45 1.26 1.26

Lime 0.00 0.37 0.33 0.50 1.18 2.84 3.45 0.00 0.00

Portlandite 0.10 0.09 0.11 0.09 0.09 0.20 0.41 0.09 0.09

Anhydrite 0.20 0.37 0.41 0.66 1.98 1.56 0.73 0.18 0.18

Calcium Langbeinite 0.00 0.00 0.00 0.16 0.26 0.11 0.14 0.00 0.00

Aphthitalite 0.00 0.00 0.07 0.00 0.17 0.00 0.00 0.00 0.00

Arcanite 0.00 0.00 0.16 0.09 0.00 0.06 0.06 0.00 0.00

Calcium Sulfoaluminate 0.00 0.00 0.00 0.09 0.06 0.14 0.06 0.00 0.00

Sylvite 0.00 0.32 0.11 0.03 0.02 0.39 0.04 0.00 0.00

Calcium Chloride 0.00 0.00 0.00 0.05 0.00 0.00 0.00 0.00 0.00

Amorphous 0.00 0.05 3.21 1.11 2.93 1.83 3.50 0.00 0.00

Akermanite 0.00 0.00 0.00 0.00 0.00 0.11 0.00 0.00 0.00

Calcium Dialuminium Oxide 0.00 0.00 0.00 0.00 0.04 0.14 0.10 0.00 0.00

Mullite 0.00 0.00 0.41 0.00 0.00 0.00 0.00 0.00 0.00

291

Table D.6 Mineralogical Composition of TI Blends with 20% Replacement


20% TI CKD B

20% TI CKD C

20% TI CKD D

20% TI CKD E

20% TI CKD F

20% TI CKD LS 20%

TI CKD SLX 20%

Alite 68.60 55.12 54.88 55.08 55.18 55.24 55.06 54.88 54.88

ß-Belite 10.30 12.62 9.78 10.34 9.44 10.94 9.02 8.24 8.24

Aluminate 8.70 7.06 7.06 7.10 7.06 7.24 7.06 6.96 6.96

Brownmillerite 7.50 6.04 6.12 6.12 6.00 6.48 6.10 6.00 6.00

Gypsum 1.70 1.36 1.36 1.36 1.36 1.36 1.36 1.36 1.36

Hemihydrate 0.50 0.40 0.40 0.40 0.40 0.40 0.40 0.40 0.40

Calcite 0.70 11.08 7.50 10.82 5.10 0.80 1.40 20.16 0.93

Quartz 0.30 2.08 1.68 2.40 0.88 1.54 1.44 0.64 19.87

Dolomite 0.00 0.90 0.62 0.00 0.20 0.00 0.00 0.00 0.00

Periclase 1.40 1.24 1.26 1.14 1.18 1.54 1.50 1.12 1.12

Lime 0.00 0.74 0.66 1.00 2.36 5.68 6.90 0.00 0.00

Portlandite 0.10 0.08 0.12 0.08 0.08 0.30 0.72 0.08 0.08

Anhydrite 0.20 0.54 0.62 1.12 3.76 2.92 1.26 0.16 0.16


Aphthitalite 0.00 0.00 0.14 0.00 0.34 0.00 0.00 0.00 0.00

Arcanite 0.00 0.00 0.32 0.18 0.00 0.12 0.12 0.00 0.00


Sylvite 0.00 0.64 0.22 0.06 0.04 0.78 0.08 0.00 0.00


Amorphous 0.00 0.10 6.42 2.22 5.86 3.66 7.00 0.00 0.00

Akermanite 0.00 0.00 0.00 0.00 0.00 0.22 0.00 0.00 0.00


Mullite 0.00 0.00 0.82 0.00 0.00 0.00 0.00 0.00 0.00

292

Table D.7 Mineralogical Composition of TII Blends with 10% Replacement

Components TII TII CKD A 10%

TII CKD B 10%

TII CKD C 10%

TII CKD D 10%

TII CKD E 10%

TII CKD F 10%

TII CKD LS 10%

TII CKD SLX 10%

Alite - M3 66.50 59.97 59.85 59.95 60.00 60.03 59.94 59.85 59.85

ß-Belite 15.20 15.87 14.45 14.73 14.28 15.03 14.07 13.68 13.68

Aluminate 3.00 2.75 2.75 2.77 2.75 2.84 2.75 2.70 2.70

Brownmillerite 8.90 8.03 8.07 8.07 8.01 8.25 8.06 8.01 8.01

Gypsum 1.00 0.90 0.90 0.90 0.90 0.90 0.90 0.90 0.90

Hemihydrate 0.60 0.54 0.54 0.54 0.54 0.54 0.54 0.54 0.54

Calcite 0.80 5.98 4.19 5.85 2.99 0.84 1.14 10.52 0.91

Quartz 0.20 1.10 0.90 1.26 0.50 0.83 0.78 0.38 10.00

Dolomite 0.00 0.45 0.31 0.00 0.10 0.00 0.00 0.00 0.00

Periclase 2.50 2.31 2.32 2.26 2.28 2.46 2.44 2.25 2.25

Lime 0.20 0.55 0.51 0.68 1.36 3.02 3.63 0.18 0.18

Portlandite 0.40 0.36 0.38 0.36 0.36 0.47 0.68 0.36 0.36

Anhydrite 0.90 1.00 1.04 1.29 2.61 2.19 1.36 0.81 0.81


Aphthitalite 0.00 0.00 0.07 0.00 0.17 0.00 0.00 0.00 0.00

Arcanite 0.00 0.00 0.16 0.09 0.00 0.06 0.06 0.00 0.00


Sylvite 0.00 0.32 0.11 0.03 0.02 0.39 0.04 0.00 0.00


Amorphous 0.00 0.05 3.21 1.11 2.93 1.83 3.50 0.00 0.00

Akermanite 0.00 0.00 0.00 0.00 0.00 0.11 0.00 0.00 0.00


Mullite 0.00 0.00 0.41 0.00 0.00 0.00 0.00 0.00 0.00

293

Table D.8 Mineralogical Composition of TII Blends with 20% Replacement

Components TII TII CKD A 20%

TII CKD B 20%

TII CKD C 20%

TII CKD D 20%

TII CKD E 20%

TII CKD F 20%

TII CKD LS 20%

TII CKD SLX 20%

Alite - M3 66.50 53.44 53.20 53.40 53.50 53.56 53.38 53.20 53.20

ß-Belite 15.20 16.54 13.70 14.26 13.36 14.86 12.94 12.16 12.16

Aluminate 3.00 2.50 2.50 2.54 2.50 2.68 2.50 2.40 2.40

Brownmillerite 8.90 7.16 7.24 7.24 7.12 7.60 7.22 7.12 7.12

Gypsum 1.00 0.80 0.80 0.80 0.80 0.80 0.80 0.80 0.80

Hemihydrate 0.60 0.48 0.48 0.48 0.48 0.48 0.48 0.48 0.48

Calcite 0.80 11.16 7.58 10.90 5.18 0.88 1.48 20.24 1.01

Quartz 0.20 2.00 1.60 2.32 0.80 1.46 1.36 0.56 19.79

Dolomite 0.00 0.90 0.62 0.00 0.20 0.00 0.00 0.00 0.00

Periclase 2.50 2.12 2.14 2.02 2.06 2.42 2.38 2.00 2.00

Lime 0.20 0.90 0.82 1.16 2.52 5.84 7.06 0.16 0.16

Portlandite 0.40 0.32 0.36 0.32 0.32 0.54 0.96 0.32 0.32

Anhydrite 0.90 1.10 1.18 1.68 4.32 3.48 1.82 0.72 0.72


Aphthitalite 0.00 0.00 0.14 0.00 0.34 0.00 0.00 0.00 0.00

Arcanite 0.00 0.00 0.32 0.18 0.00 0.12 0.12 0.00 0.00


Sylvite 0.00 0.64 0.22 0.06 0.04 0.78 0.08 0.00 0.00


Amorphous 0.00 0.10 6.42 2.22 5.86 3.66 7.00 0.00 0.00

Akermanite 0.00 0.00 0.00 0.00 0.00 0.22 0.00 0.00 0.00


Mullite 0.00 0.00 0.82 0.00 0.00 0.00 0.00 0.00 0.00

294

Table D.9 Particle Size Distributions of CKD-PC and PC-filler Blends

Description TI TI CKD A

10% TI CKD B

10% TI CKD C

10% TI CKD D

10% TI CKD E

10% TI CKD F

10% TI CKD LS 10%

TI CKD SLX 10%

< 3.0887 8.59 9.12 9.17 9.41 9.24 8.44 9.03 9.59 9.75

<10.4804 36.69 37.19 36.80 37.37 38.30 35.58 36.82 38.58 37.78

< 22.4909 65.02 64.80 63.96 64.70 65.99 63.51 64.56 67.01 65.80

< 30.5252 78.31 77.52 76.55 77.36 78.58 76.58 77.46 79.69 78.83

< 41.4295 89.55 88.32 87.26 88.17 89.22 87.79 88.46 90.26 89.81

< 48.2654 93.65 92.34 91.25 92.21 93.16 91.99 92.55 94.10 93.81

3-30 um 69.72 68.40 67.38 67.95 69.34 68.14 68.43 70.10 69.08

30-48 um 15.34 14.82 14.71 14.85 14.58 15.41 15.09 14.40 14.98

Description TI TI CKD A

20% TI CKD B

20% TI CKD C

20% TI CKD D

20% TI CKD E

20% TI CKD F

20% TI CKD LS 20%

TI CKD SLX 20%

< 3.0887 8.59 9.66 9.75 10.24 9.90 8.29 9.47 10.58 10.91

<10.4804 36.69 37.68 36.91 38.05 39.92 34.46 36.95 40.47 38.86

< 22.4909 65.02 64.58 62.90 64.37 66.96 61.99 64.11 69.00 66.58

< 30.5252 78.31 76.73 74.78 76.41 78.85 74.86 76.60 81.07 79.35

< 41.4295 89.55 87.10 84.97 86.79 88.90 86.03 87.36 90.97 90.07

< 48.2654 93.65 91.03 88.85 90.77 92.66 90.32 91.45 94.54 93.98

3-30 um 69.72 67.07 65.03 66.17 68.95 66.56 67.14 70.49 68.44

30-48 um 15.34 14.30 14.07 14.36 13.81 15.47 14.84 13.47 14.62


TII CKD B 10%

TII CKD C 10%

TII CKD D 10%

TII CKD E 10%

TII CKD F 10%

TII CKD LS 10%

TII CKD SLX 10%

< 3.0887 10.56 10.89 10.94 11.18 11.01 10.21 10.80 11.36 11.52

<10.4804 39.09 39.35 38.96 39.53 40.46 37.74 38.98 40.74 39.94

< 22.4909 67.39 66.93 66.09 66.83 68.12 65.64 66.69 69.14 67.93

< 30.5252 79.35 78.46 77.48 78.30 79.52 77.52 78.39 80.63 79.77

< 41.4295 89.10 87.92 86.86 87.77 88.82 87.39 88.05 89.86 89.41

< 48.2654 92.73 91.51 90.42 91.38 92.32 91.16 91.72 93.26 92.98

3-30 um 68.80 67.56 66.55 67.11 68.50 67.31 67.60 69.27 68.25

30-48 um 13.38 13.05 12.94 13.08 12.81 13.63 13.32 12.63 13.21


TII CKD B 20%

TII CKD C 20%

TII CKD D 20%

TII CKD E 20%

TII CKD F 20%

TII CKD LS 20%

TII CKD SLX 20%

< 3.0887 10.56 11.23 11.32 11.81 11.47 9.87 11.04 12.16 12.49

<10.4804 39.09 39.60 38.83 39.97 41.83 36.38 38.86 42.39 40.78

< 22.4909 67.39 66.47 64.80 66.27 68.85 63.88 66.00 70.89 68.47

< 30.5252 79.35 77.56 75.61 77.24 79.68 75.69 77.44 81.90 80.19

< 41.4295 89.10 86.74 84.61 86.43 88.54 85.67 87.01 90.62 89.71

< 48.2654 92.73 90.29 88.11 90.03 91.92 89.58 90.71 93.80 93.24

3-30 um 68.80 66.33 64.29 65.43 68.21 65.82 66.40 69.75 67.70

30-48 um 13.38 12.72 12.50 12.78 12.24 13.89 13.27 11.89 13.05

295

Appendix E. Isothermal Conduction Calorimetry Results

296

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TI LS 10%

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TI CKD D2 10%

TI LS 10%

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TI CKD E 10%

TI LS 10%

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TI CKD F 10%

TI LS 10%

Figure E.1 Heat of Hydration of TI cement with 10% replacement of limestone (LS), silica flour (SLX), and six CKDs (A, B, C, D, E and F).

297

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TI SLX 20%

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TI CKD A 20%

TI LS 20%

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TI CKD B 20%

TI LS 20%

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TI CKD C 20%

TI LS 20%

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TI CKD D2 20%

TI LS 20%

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TI CKD E 20%

TI LS 20%

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TI CKD F 20%

TI LS 20%

`

Figure E.2 Heat of Hydration of TI cement with 20% replacement of limestone (LS), silica flour (SLX), and six CKDs (A, B, C, D, E and F).

298

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TII

TII LS 10%

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TII SLX 10%

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TII CKD A 10%

TII LS 10%

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TII CKD B 10%

TII LS 10%

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TII CKD C 10%

TII LS 10%

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TII CKD D2 10%

TII LS 10%

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TII CKD E 10%

TII LS 10%

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TII CKD F 10%

TII LS 10%

Figure E.3 Heat of Hydration of TII cement with 10% replacement of limestone (LS), silica flour (SLX), and six CKDs (A, B, C, D, E and F).

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TII LS 20%

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TII CKD A 20%

TII LS 20%

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TII CKD B 20%

TII LS 20%

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TII CKD C 20%

TII LS 20%

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TII CKD F 20%

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Figure E.4 Heat of Hydration of TII cement with 20% replacement of limestone (LS), silica flour (SLX), and six CKDs (A, B, C, D, E and F).

300

Appendix F. Mortar Flow Statistical Analysis

301

Table F.1 Mortar Flow Raw Data

TI Blends flow TII Blends flow

TI 109 TII 112

TI 107 TII 113

TI 105 TII 116

TI 107 TII 115

TI 109 TII 115

TI 108 TII 118

TI 102 TII 113

TI CKD LS 10% 110 TII CKD LS 10% 116

TI CKD LS 10% 114 TII CKD LS 10% 117

TI CKD SLX 10% 112 TII CKD SLX 10% 115

TI CKD SLX 10% 111 TII CKD SLX 10% 117

TI CKD A 10% 108 TII CKD A 10% 108

TI CKD A 10% 103 TII CKD A 10% 110

TI CKD A 10% 100 TII CKD B 10% 109

TI CKD B 10% 102 TII CKD B 10% 115

TI CKD B 10% 101 TII CKD C 10% 106

TI CKD B 10% 98 TII CKD C 10% 112

TI CKD C 10% 101 TII CKD D 10% 111

TI CKD C 10% 101 TII CKD D 10% 116

TI CKD D 10% 110 TII CKD E 10% 100

TI CKD D 10% 110 TII CKD E 10% 106

TI CKD E 10% 101 TII CKD F 10% 98

TI CKD E 10% 107 TII CKD F 10% 102

TI CKD E 10% 106 TII CKD LS 20% 116

TI CKD E 10% 96 TII CKD LS 20% 120

TI CKD E 10% 101 TII CKD SLX 20% 114

TI CKD F 10% 96 TII CKD SLX 20% 120

TI CKD F 10% 98 TII CKD A 20% 105

TI CKD F 10% 87 TII CKD A 20% 108

TI CKD F 10% 94 TII CKD B 20% 100

TI CKD LS 20% 117 TII CKD B 20% 105

TI CKD LS 20% 117 TII CKD C 20% 103

TI CKD SLX 20% 113 TII CKD C 20% 107

TI CKD SLX 20% 114 TII CKD D 20% 109

TI CKD A 20% 101 TII CKD D 20% 109

TI CKD A 20% 103 TII CKD E 20% 82

TI CKD B 20% 93 TII CKD E 20% 98

TI CKD B 20% 97 TII CKD F 20% 70

TI CKD C 20% 100 TII CKD F 20% 86

TI CKD C 20% 103 (b)

TI CKD D 20% 107

TI CKD D 20% 109

TI CKD E 20% 80

TI CKD E 20% 76

TI CKD E 20% 80

TI CKD F 20% 63

TI CKD F 20% 74

TI CKD F 20% 61

TI CKD F 20% 69

(a)

302

Oneway Analysis of Flow By Cement TI Blends

60

70

80

90

100

110

120

flow

TI

TI C

KD

A 1

0%

TI C

KD

A 2

0%

TI C

KD

B 1

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TI C

KD

B 2

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TI C

KD

C 1

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TI C

KD

C 2

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TI C

KD

D 1

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TI C

KD

D 2

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TI C

KD

E 1

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TI C

KD

E 2

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TI C

KD

F 1

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TI C

KD

F 2

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TI C

KD

LS

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TI C

KD

LS

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TI C

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TI C

KD

SLX

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TI Blends

Oneway Anova Summary of Fit Rsquare 0.958229 Adj Rsquare 0.937343 Root Mean Square Error 3.363037 Mean of Response 99.63776 Observations (or Sum Wgts) 49

Analysis of Variance Source DF Sum of Squares Mean Square F Ratio Prob > F TI Blends 16 8302.4621 518.904 45.8800 <.0001 Error 32 361.9205 11.310 C. Total 48 8664.3827

Means for Oneway Anova Level Number Mean Std Error Lower 95% Upper 95% TI 7 106.571 1.2711 103.98 109.16 TI CKD A 10% 3 103.583 1.9417 99.63 107.54 TI CKD A 20% 2 101.750 2.3780 96.91 106.59 TI CKD B 10% 3 100.333 1.9417 96.38 104.29 TI CKD B 20% 2 94.625 2.3780 89.78 99.47 TI CKD C 10% 2 101.000 2.3780 96.16 105.84 TI CKD C 20% 2 101.250 2.3780 96.41 106.09 TI CKD D 10% 2 109.750 2.3780 104.91 114.59 TI CKD D 20% 2 108.000 2.3780 103.16 112.84 TI CKD E 10% 5 102.050 1.5040 98.99 105.11 TI CKD E 20% 3 78.417 1.9417 74.46 82.37 TI CKD F 10% 4 93.563 1.6815 90.14 96.99 TI CKD F 20% 4 66.313 1.6815 62.89 69.74 TI CKD LS 10% 2 112.000 2.3780 107.16 116.84 TI CKD LS 20% 2 116.500 2.3780 111.66 121.34 TI CKD SLX 10% 2 111.250 2.3780 106.41 116.09 TI CKD SLX 20% 2 113.625 2.3780 108.78 118.47 Std Error uses a pooled estimate of error variance

303

Oneway Analysis of Flow By Cement TI Blends

60

70

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120

flow

TI

TI C

KD

A 1

0%

TI C

KD

A 2

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TI C

KD

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TI C

KD

B 2

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TI C

KD

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TI C

KD

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TI C

KD

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TI C

KD

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TI C

KD

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TI C

KD

E 2

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TI C

KD

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TI C

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TI C

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LS

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TI C

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SLX

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TI C

KD

SLX

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TI Blends

Means and Std Deviations Level Number Mean Std Dev Std Err Mean Lower 95% Upper 95% TI 7 106.571 2.37484 0.8976 104.38 108.77 TI CKD A 10% 3 103.583 3.66003 2.1131 94.49 112.68 TI CKD A 20% 2 101.750 1.06066 0.7500 92.22 111.28 TI CKD B 10% 3 100.333 2.08167 1.2019 95.16 105.50 TI CKD B 20% 2 94.625 2.65165 1.8750 70.80 118.45 TI CKD C 10% 2 101.000 0.00000 0.0000 101.00 101.00 TI CKD C 20% 2 101.250 2.47487 1.7500 79.01 123.49 TI CKD D 10% 2 109.750 0.35355 0.2500 106.57 112.93 TI CKD D 20% 2 108.000 1.41421 1.0000 95.29 120.71 TI CKD E 10% 5 102.050 4.49444 2.0100 96.47 107.63 TI CKD E 20% 3 78.417 2.55359 1.4743 72.07 84.76 TI CKD F 10% 4 93.563 4.70981 2.3549 86.07 101.06 TI CKD F 20% 4 66.313 5.94199 2.9710 56.86 75.77 TI CKD LS 10% 2 112.000 2.82843 2.0000 86.59 137.41 TI CKD LS 20% 2 116.500 0.00000 0.0000 116.50 116.50 TI CKD SLX 10% 2 111.250 1.06066 0.7500 101.72 120.78 TI CKD SLX 20% 2 113.625 0.88388 0.6250 105.68 121.57

304

Oneway Analysis of flow By Cement TII Blends

60

70

80

90

100

110

120

130

flow

TII

TII C

KD

A 1

0%

TII C

KD

A 2

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TII C

KD

B 1

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TII C

KD

B 2

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TII C

KD

C 1

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TII C

KD

C 2

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TII C

KD

D 1

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TII C

KD

D 2

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TII C

KD

E 1

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TII C

KD

E 2

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TII C

KD

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TII C

KD

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LS

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LS

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TII Blends


Analysis of Variance Source DF Sum of Squares Mean Square F Ratio Prob > F TII Blends 16 3810.9643 238.185 12.6610 <.0001 Error 22 413.8743 18.812 C. Total 38 4224.8386

Means for Oneway Anova Level Number Mean Std Error Lower 95% Upper 95% TII 7 114.429 1.6394 111.03 117.83 TII CKD A 10% 2 108.750 3.0670 102.39 115.11 TII CKD A 20% 2 106.375 3.0670 100.01 112.74 TII CKD B 10% 2 111.625 3.0670 105.26 117.99 TII CKD B 20% 2 102.375 3.0670 96.01 108.74 TII CKD C 10% 2 108.950 3.0670 102.59 115.31 TII CKD C 20% 2 104.750 3.0670 98.39 111.11 TII CKD D 10% 2 113.375 3.0670 107.01 119.74 TII CKD D 20% 2 109.000 3.0670 102.64 115.36 TII CKD E 10% 2 103.000 3.0670 96.64 109.36 TII CKD E 20% 2 89.625 3.0670 83.26 95.99 TII CKD F 10% 2 99.625 3.0670 93.26 105.99 TII CKD F 20% 2 77.500 3.0670 71.14 83.86 TII CKD LS 10% 2 116.375 3.0670 110.01 122.74 TII CKD LS 20% 2 117.875 3.0670 111.51 124.24 TII CKD SLX 10% 2 116.000 3.0670 109.64 122.36 TII CKD SLX 20% 2 116.800 3.0670 110.44 123.16 Std Error uses a pooled estimate of error variance

305

Oneway Analysis of flow By Cement TII Blends

60

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90

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130

flow

TII

TII C

KD

A 1

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TII C

KD

A 2

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TII C

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TII C

KD

B 2

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TII C

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TII C

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TII C

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TII C

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TII C

KD

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TII C

KD

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TII C

KD

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TII C

KD

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TII Blends

Means and Std Deviations Level Number Mean Std Dev Std Err Mean Lower 95% Upper 95% TII 7 114.429 1.9133 0.7232 112.7 116.20 TII CKD A 10% 2 108.750 1.4142 1.0000 96.0 121.46 TII CKD A 20% 2 106.375 2.6517 1.8750 82.6 130.20 TII CKD B 10% 2 111.625 4.4194 3.1250 71.9 151.33 TII CKD B 20% 2 102.375 3.7123 2.6250 69.0 135.73 TII CKD C 10% 2 108.950 3.9598 2.8000 73.4 144.53 TII CKD C 20% 2 104.750 2.8284 2.0000 79.3 130.16 TII CKD D 10% 2 113.375 4.0659 2.8750 76.8 149.91 TII CKD D 20% 2 109.000 0.0000 0.0000 109.0 109.00 TII CKD E 10% 2 103.000 3.8891 2.7500 68.1 137.94 TII CKD E 20% 2 89.625 11.1369 7.8750 -10.4 189.69 TII CKD F 10% 2 99.625 2.6517 1.8750 75.8 123.45 TII CKD F 20% 2 77.500 11.3137 8.0000 -24.1 179.15 TII CKD LS 10% 2 116.375 0.5303 0.3750 111.6 121.14 TII CKD LS 20% 2 117.875 3.3588 2.3750 87.7 148.05 TII CKD SLX 10% 2 116.000 1.7678 1.2500 100.1 131.88 TII CKD SLX 20% 2 116.800 4.5255 3.2000 76.1 157.46

306

Appendix G. Mortar Compressive Strength Statistical Analysis

307

Table G.1 Individual Compressive Strength (MPa)

TI Blends 1d 3d 7d 28d 90d TII Blends 1d 3d 7d 28d 90d

TI 15.9 26.4 27.6 36.6 40.2 TII 13.8 23.1 27.8 36.5 42.8

TI 16.0 25.2 29.3 35.5 42.1 TII 13.3 23.7 28.2 36.7 42.2

TI 15.9 24.3 29.4 36.5 39.8 TII 14.3 21.6 27.1 37.7 42.0

TI CKD LS 10% 15.1 26.8 31.5 36.0 45.3 TII CKD LS 10% 13.1 21.5 29.1 36.8 42.2



TI CKD SLX 10% 15.5 24.5 27.8 34.4 39.2 TII CKD SLX 10% 11.7 19.2 22.7 30.7 35.2



TI CKD A 10% 17.9 27.4 32.2 37.5 44.4 TII CKD A 10% 15.6 23.6 28.9 34.6 39.9

TI CKD A 10% 17.9 28.6 32.5 37.3 43.7 TII CKD A 10% 14.8 23.8 29.3 37.1 42.6

TI CKD A 10% 17.8 27.9 32.6 38.4 44.9 TII CKD A 10% 14.8 23.3 27.8 36.5 43.4

TI CKD B 10% 16.0 26.8 30.5 35.8 42.0 TII CKD B 10% 14.3 22.2 28.3 35.6 43.2

TI CKD B 10% 16.4 25.7 30.1 38.0 42.6 TII CKD B 10% 14.1 23.5 29.3 34.8 42.2

TI CKD B 10% 16.1 26.6 29.3 37.2 39.7 TII CKD B 10% 15.6 24.2 26.3 35.6 40.8

TI CKD C 10% 15.3 26.6 29.6 36.1 40.6 TII CKD C 10% 14.4 23.0 27.8 34.2 42.2

TI CKD C 10% 14.8 26.3 28.9 35.8 38.8 TII CKD C 10% 14.6 23.4 25.8 34.0 41.8

TI CKD C 10% 15.1 26.5 30.7 38.2 38.9 TII CKD C 10% 15.1 23.7 27.9 35.1 40.4

TI CKD D 10% 11.9 24.5 32.5 41.7 43.3 TII CKD D 10% 12.7 21.2 25.9 34.7 40.6

TI CKD D 10% 11.5 24.5 31.4 39.9 47.1 TII CKD D 10% 12.7 21.6 26.4 34.2 43.4

TI CKD D 10% 11.6 24.0 32.6 41.9 47.6 TII CKD D 10% 13.0 21.3 26.0 35.4 42.7

TI CKD E 10% 15.2 26.2 33.0 36.2 44.3 TII CKD E 10% 14.7 24.0 28.9 36.4 43.0

TI CKD E 10% 14.2 26.8 32.4 36.9 43.6 TII CKD E 10% 15.2 23.5 30.1 36.1 42.3

TI CKD E 10% 14.9 27.0 31.8 36.4 43.5 TII CKD E 10% 15.1 24.3 30.2 38.4 44.2

TI CKD F 10% 14.4 27.2 33.1 37.9 41.1 TII CKD F 10% 13.3 22.0 27.7 40.0 43.6

TI CKD F 10% 14.5 27.6 31.4 40.2 41.5 TII CKD F 10% 13.8 22.7 29.6 38.3 41.2

TI CKD F 10% 14.0 27.3 31.0 39.8 41.6 TII CKD F 10% 14.1 23.9 30.1 36.9 42.3







TI CKD A 20% 15.5 25.1 28.7 34.4 40.1 TII CKD A 20% 13.7 22.5 26.1 32.8 39.3

TI CKD A 20% 16.2 24.6 29.2 33.9 40.7 TII CKD A 20% 12.9 21.5 26.4 32.5 37.4

TI CKD A 20% 15.6 26.1 29.2 34.7 40.9 TII CKD A 20% 13.3 21.5 25.6 32.0 37.0

TI CKD B 20% 14.2 24.0 27.3 33.3 39.7 TII CKD B 20% 13.9 21.8 27.2 31.1 38.0

TI CKD B 20% 14.2 24.0 28.0 33.6 38.9 TII CKD B 20% 13.9 21.2 26.5 30.8 40.2

TI CKD B 20% 14.6 23.3 27.8 34.6 40.0 TII CKD B 20% 14.4 22.1 26.8 31.0 36.6

TI CKD C 20% 13.0 24.8 28.4 33.9 37.5 TII CKD C 20% 12.6 20.4 24.2 30.5 37.4

TI CKD C 20% 13.7 24.8 29.0 33.0 37.9 TII CKD C 20% 11.6 21.4 26.2 31.5 39.3

TI CKD C 20% 13.2 24.2 28.1 29.9 37.3 TII CKD C 20% 12.3 21.2 25.5 30.8 37.1

TI CKD D 20% 10.7 18.2 22.4 37.8 46.8 TII CKD D 20% 11.1 15.9 20.5 31.7 42.1

TI CKD D 20% 10.2 17.9 23.9 37.7 45.2 TII CKD D 20% 10.6 16.6 19.4 35.1 43.1

TI CKD D 20% 10.4 17.6 21.6 34.0 44.2 TII CKD D 20% 10.5 15.8 21.5 32.8 40.5

TI CKD E 20% 10.9 21.4 28.3 36.8 42.6 TII CKD E 20% 11.1 18.1 24.1 35.3 41.3

TI CKD E 20% 10.6 21.4 27.8 35.4 42.9 TII CKD E 20% 10.6 18.4 25.9 33.1 38.3

TI CKD E 20% 11.0 23.6 29.6 35.9 42.5 TII CKD E 20% 11.6 17.4 25.0 32.8 39.4

TI CKD F 20% 11.8 24.5 30.7 35.4 42.5 TII CKD F 20% 11.8 19.8 28.5 36.1 40.8

TI CKD F 20% 11.4 22.8 32.1 36.7 42.5 TII CKD F 20% 11.7 20.7 28.2 37.0 40.8

TI CKD F 20% 11.3 23.7 33.1 35.9 42.2 TII CKD F 20% 12.0 20.8 28.5 35.6 39.2

(a) (b)

308

Table G.2 Average Compressive Strengths

MPa Percentage of TI

1d 3d 7d 28d 90d 1d 3d 7d 28d 90d

TI 15.9 25.3 28.7 36.0 40.0 100% 100% 100% 100% 100%

TI LS 10% 14.9 25.9 30.3 37.2 44.0 93% 103% 105% 103% 110%

TI SLX 10% 15.2 24.0 28.1 35.0 38.8 96% 95% 98% 97% 97%

TI CKD A 10% 17.9 27.9 32.4 37.7 44.3 112% 110% 113% 105% 111%

TI CKD B 10% 16.2 26.4 30.0 37.0 41.5 102% 104% 104% 103% 104%

TI CKD C 10% 15.1 26.5 29.7 36.7 39.4 95% 105% 104% 102% 99%

TI CKD D 10% 11.7 24.3 32.1 41.2 46.0 73% 96% 112% 114% 115%

TI CKD E 10% 14.8 26.7 32.4 36.5 45.4 93% 105% 113% 101% 114%

TI CKD F 10% 14.3 27.4 31.8 39.3 41.4 90% 108% 111% 109% 104%

TI LS 20% 12.5 22.6 27.1 33.1 37.6 78% 89% 94% 92% 94%

TI SLX 20% 13.2 21.1 25.4 31.6 34.8 83% 83% 88% 88% 87%

TI CKD A 20% 15.7 25.3 29.0 34.3 40.6 99% 100% 101% 95% 102%

TI CKD B 20% 14.3 23.8 27.7 33.8 39.5 90% 94% 96% 94% 99%

TI CKD C 20% 13.3 24.6 28.5 32.3 37.6 84% 97% 99% 90% 94%

TI CKD D 20% 10.4 17.9 22.2 35.7 45.4 65% 71% 77% 99% 114%

TI CKD E 20% 10.8 22.1 27.3 36.0 42.7 68% 87% 95% 100% 107%

TI CKD F 20% 11.5 23.7 30.7 36.0 42.3 72% 94% 107% 100% 106%

MPa Percentage of TII

1d 3d 7d 28d 90d 1d 3d 7d 28d 90d

TII 13.8 22.6 27.6 37.0 42.5 100% 100% 100% 100% 100%

TII LS 10% 12.8 21.5 28.7 35.7 41.2 93% 95% 104% 97% 97%

TII SLX 10% 12.2 19.8 23.4 30.7 35.4 88% 87% 85% 83% 83%

TII CKD A 10% 15.0 23.6 28.7 36.1 42.0 109% 104% 104% 98% 99%

TII CKD B 10% 14.6 23.3 28.0 35.3 42.1 106% 103% 101% 96% 99%

TII CKD C 10% 14.7 23.3 27.2 34.4 41.5 107% 103% 98% 93% 98%

TII CKD D 10% 12.8 21.3 26.1 34.8 41.4 93% 94% 94% 94% 97%

TII CKD E 10% 15.0 23.9 29.7 36.9 42.3 109% 106% 108% 100% 100%

TII CKD F 10% 13.7 22.9 29.2 38.4 42.4 99% 101% 105% 104% 100%

TII LS 20% 11.0 18.4 24.7 30.4 34.9 80% 81% 89% 82% 82%

TII SLX 20% 11.1 18.3 20.0 27.5 31.0 80% 81% 72% 74% 73%

TII CKD A 20% 13.3 21.8 26.0 32.4 37.9 96% 96% 94% 88% 89%

TII CKD B 20% 14.1 21.7 26.8 31.0 38.3 102% 96% 97% 84% 90%

TII CKD C 20% 12.2 21.0 25.3 30.9 37.9 88% 93% 92% 84% 89%

TII CKD D 20% 10.7 16.1 20.5 33.2 41.0 78% 71% 74% 90% 96%

TII CKD E 20% 10.9 18.0 25.4 33.7 38.8 79% 79% 92% 91% 91%

TII CKD F 20% 11.8 20.5 28.4 37.7 40.3 86% 90% 103% 102% 95%

309

Oneway Analysis of 1d By Cement TI Blends

10

11

12

13

14

15

16

17

18

1d

TI

TI C

KD

A 1

0%

TI C

KD

A 2

0%

TI C

KD

B 1

0%

TI C

KD

B 2

0%

TI C

KD

C 1

0%

TI C

KD

C 2

0%

TI C

KD

D 1

0%

TI C

KD

D 2

0%

TI C

KD

E 1

0%

TI C

KD

E 2

0%

TI C

KD

F 1

0%

TI C

KD

F 2

0%

TI C

KD

LS

10%

TI C

KD

LS

20%

TI C

KD

SLX

10%

TI C

KD

SLX

20%

TI Blends




310

Oneway Analysis of 1d By Cement TII Blends

10

11

12

13

14

15

16

1d

TII

TII C

KD

A 1

0%

TII C

KD

A 2

0%

TII C

KD

B 1

0%

TII C

KD

B 2

0%

TII C

KD

C 1

0%

TII C

KD

C 2

0%

TII C

KD

D 1

0%

TII C

KD

D 2

0%

TII C

KD

E 1

0%

TII C

KD

E 2

0%

TII C

KD

F 1

0%

TII C

KD

F 2

0%

TII C

KD

LS

10%

TII C

KD

LS

20%

TII C

KD

SLX

10%

TII C

KD

SLX

20%

TII Blends




311


16

18

20

22

24

26

28

30

3d

TI

TI C

KD

A 1

0%

TI C

KD

A 2

0%

TI C

KD

B 1

0%

TI C

KD

B 2

0%

TI C

KD

C 1

0%

TI C

KD

C 2

0%

TI C

KD

D 1

0%

TI C

KD

D 2

0%

TI C

KD

E 1

0%

TI C

KD

E 2

0%

TI C

KD

F 1

0%

TI C

KD

F 2

0%

TI C

KD

LS

10%

TI C

KD

LS

20%

TI C

KD

SLX

10%

TI C

KD

SLX

20%

TI Blends




312


15

16

17

18

19

20

21

22

23

24

25

3d

TII

TII C

KD

A 1

0%

TII C

KD

A 2

0%

TII C

KD

B 1

0%

TII C

KD

B 2

0%

TII C

KD

C 1

0%

TII C

KD

C 2

0%

TII C

KD

D 1

0%

TII C

KD

D 2

0%

TII C

KD

E 1

0%

TII C

KD

E 2

0%

TII C

KD

F 1

0%

TII C

KD

F 2

0%

TII C

KD

LS

10%

TII C

KD

LS

20%

TII C

KD

SLX

10%

TII C

KD

SLX

20%

TII Blends




313


20

22

24

26

28

30

32

34

7d

TI

TI C

KD

A 1

0%

TI C

KD

A 2

0%

TI C

KD

B 1

0%

TI C

KD

B 2

0%

TI C

KD

C 1

0%

TI C

KD

C 2

0%

TI C

KD

D 1

0%

TI C

KD

D 2

0%

TI C

KD

E 1

0%

TI C

KD

E 2

0%

TI C

KD

F 1

0%

TI C

KD

F 2

0%

TI C

KD

LS

10%

TI C

KD

LS

20%

TI C

KD

SLX

10%

TI C

KD

SLX

20%

TI Blends




314


18

20

22

24

26

28

30

32

7d

TII

TII C

KD

A 1

0%

TII C

KD

A 2

0%

TII C

KD

B 1

0%

TII C

KD

B 2

0%

TII C

KD

C 1

0%

TII C

KD

C 2

0%

TII C

KD

D 1

0%

TII C

KD

D 2

0%

TII C

KD

E 1

0%

TII C

KD

E 2

0%

TII C

KD

F 1

0%

TII C

KD

F 2

0%

TII C

KD

LS

10%

TII C

KD

LS

20%

TII C

KD

SLX

10%

TII C

KD

SLX

20%

TII Blends




315


28

30

32

34

36

38

40

42

28d

TI

TI C

KD

A 1

0%

TI C

KD

A 2

0%

TI C

KD

B 1

0%

TI C

KD

B 2

0%

TI C

KD

C 1

0%

TI C

KD

C 2

0%

TI C

KD

D 1

0%

TI C

KD

D 2

0%

TI C

KD

E 1

0%

TI C

KD

E 2

0%

TI C

KD

F 1

0%

TI C

KD

F 2

0%

TI C

KD

LS

10%

TI C

KD

LS

20%

TI C

KD

SLX

10%

TI C

KD

SLX

20%

TI Blends




316


26

28

30

32

34

36

38

40

42

28d

TII

TII C

KD

A 1

0%

TII C

KD

A 2

0%

TII C

KD

B 1

0%

TII C

KD

B 2

0%

TII C

KD

C 1

0%

TII C

KD

C 2

0%

TII C

KD

D 1

0%

TII C

KD

D 2

0%

TII C

KD

E 1

0%

TII C

KD

E 2

0%

TII C

KD

F 1

0%

TII C

KD

F 2

0%

TII C

KD

LS

10%

TII C

KD

LS

20%

TII C

KD

SLX

10%

TII C

KD

SLX

20%

TII Blends




317


35

40

45

50

90d

TI

TI C

KD

A 1

0%

TI C

KD

A 2

0%

TI C

KD

B 1

0%

TI C

KD

B 2

0%

TI C

KD

C 1

0%

TI C

KD

C 2

0%

TI C

KD

D 1

0%

TI C

KD

D 2

0%

TI C

KD

E 1

0%

TI C

KD

E 2

0%

TI C

KD

F 1

0%

TI C

KD

F 2

0%

TI C

KD

LS

10%

TI C

KD

LS

20%

TI C

KD

SLX

10%

TI C

KD

SLX

20%

TI Blends




318


30

32.5

35

37.5

40

42.5

45

90d

TII

TII C

KD

A 1

0%

TII C

KD

A 2

0%

TII C

KD

B 1

0%

TII C

KD

B 2

0%

TII C

KD

C 1

0%

TII C

KD

C 2

0%

TII C

KD

D 1

0%

TII C

KD

D 2

0%

TII C

KD

E 1

0%

TII C

KD

E 2

0%

TII C

KD

F 1

0%

TII C

KD

F 2

0%

TII C

KD

LS

10%

TII C

KD

LS

20%

TII C

KD

SLX

10%

TII C

KD

SLX

20%

TII Blends




319

Appendix H. Mortar Expansion in Limewater Statistical Analysis

320

Table H.1 Individual Expansions in Limewater of TI Blends

TI Blends Sample ID 14d TI Blends Sample ID 14d

TI 1 0.001 TI CKD D 10% 1 0.043

TI 2 0.000 TI CKD D 10% 2 0.040

TI 3 0.002 TI CKD D 10% 3 0.046

TI 4 0.001 average 0.001 TI CKD D 10% 4 0.044 average 0.043

TI 1 0.010 TI CKD E 10% 1 0.031

TI 2 0.008 TI CKD E 10% 2 0.029

TI 3 0.007 TI CKD E 10% 3 0.030

TI 4 0.009 average 0.008 TI CKD E 10% 4 0.029 average 0.030

TI 1 0.008 TI CKD F 10% 1 0.015

TI 2 0.008 TI CKD F 10% 2 0.017

TI 3 0.008 TI CKD F 10% 3 0.017

TI 4 0.009 average 0.008 TI CKD F 10% 4 0.017 average 0.016

TI 1 0.003 TI CKD LS 20% 1 0.006

TI 2 0.005 TI CKD LS 20% 2 0.006

TI 3 0.005 TI CKD LS 20% 3 0.006

TI 4 0.005 average 0.004 TI CKD LS 20% 4 0.006 average 0.006

TI 1 0.005 TI CKD LS 20% 1 0.003

TI 2 0.004 TI CKD LS 20% 2 0.004

TI 3 0.005 TI CKD LS 20% 3 0.003

TI 4 0.005 average 0.005 TI CKD LS 20% 4 0.003 average 0.003

TI 1 0.004 TI CKD SLX 20% 1 0.002

TI 2 0.004 TI CKD SLX 20% 2 0.004

TI 3 0.004 TI CKD SLX 20% 3 0.004

TI 4 0.003 average 0.004 TI CKD SLX 20% 4 0.004 average 0.004

TI CKD LS 10% 1 0.009 TI CKD SLX 20% 1 0.005



TI CKD LS 10% 4 0.009 average 0.009 TI CKD SLX 20% 4 0.006 average 0.005

TI CKD LS 10% 1 0.004 TI CKD A 20% 1 0.014

TI CKD LS 10% 2 0.006 TI CKD A 20% 2 0.015

TI CKD LS 10% 3 0.004 TI CKD A 20% 3 0.014

TI CKD LS 10% 4 0.004 average 0.004 TI CKD A 20% 4 0.014 average 0.014

TI CKD SLX 10% 1 0.005 TI CKD B 20% 1 0.011

TI CKD SLX 10% 2 0.006 TI CKD B 20% 2 0.010

TI CKD SLX 10% 3 0.005 TI CKD B 20% 3 0.010

TI CKD SLX 10% 4 0.006 average 0.006 TI CKD B 20% 4 0.012 average 0.011

TI CKD SLX 10% 1 0.006 TI CKD C 20% 1 0.012

TI CKD SLX 10% 2 0.006 TI CKD C 20% 2 0.012

TI CKD SLX 10% 3 0.005 TI CKD C 20% 3 0.013

TI CKD SLX 10% 4 0.005 average 0.005 TI CKD C 20% 4 0.012 average 0.012

TI CKD A 10% 1 0.009 TI CKD D 20% 1 0.1390

TI CKD A 10% 2 0.012 TI CKD D 20% 2 0.1330

TI CKD A 10% 3 0.009 TI CKD D 20% 3 0.1260

TI CKD A 10% 4 0.009 average 0.010 TI CKD D 20% 4 0.1270 average 0.131

TI CKD B 10% 1 0.007 TI CKD D 20% 1 0.124

TI CKD B 10% 2 0.007 TI CKD D 20% 2 0.126

TI CKD B 10% 3 0.009 TI CKD D 20% 3 0.124

TI CKD B 10% 4 0.008 average 0.008 TI CKD D 20% 4 0.126 average 0.125

TI CKD C 10% 1 0.007 TI CKD E 20% 1 0.067

TI CKD C 10% 2 0.007 TI CKD E 20% 2 0.062

TI CKD C 10% 3 0.006 TI CKD E 20% 3 0.071

TI CKD C 10% 4 0.007 average 0.007 TI CKD E 20% 4 0.070 average 0.068

TI CKD D 10% 1 0.058 TI CKD F 20% 1 0.033

TI CKD D 10% 2 0.059 TI CKD F 20% 2 0.034

TI CKD D 10% 3 0.056 TI CKD F 20% 3 0.033

TI CKD D 10% 4 0.055 average 0.057 TI CKD F 20% 4 0.034 average 0.034

TI CKD D 10% 1 0.059

TI CKD D 10% 2 0.057

TI CKD D 10% 3 0.058

TI CKD D 10% 4 0.059 average 0.058

321


-0.01

0.01

0.03

0.05

0.07

0.09

0.11

0.13

14d

TI

TI C

KD

A 1

0%

TI C

KD

A 2

0%

TI C

KD

B 1

0%

TI C

KD

B 2

0%

TI C

KD

C 1

0%

TI C

KD

C 2

0%

TI C

KD

D 1

0%

TI C

KD

D 2

0%

TI C

KD

E 1

0%

TI C

KD

E 2

0%

TI C

KD

F 1

0%

TI C

KD

F 2

0%

TI C

KD

LS

10%

TI C

KD

LS

20%

TI C

KD

SLX

10%

TI C

KD

SLX

20%

TI Blends




322

Table H.2 Individual Expansions in Limewater of TII Blends

TII Blends Sample 14d

TII 1 0.0070

TII 2 0.0080

TII 3 0.0080

TII 4 0.0080 average 0.008

TII 1 0.0040

TII 2 0.0060

TII 3 0.0050

TII 4 0.0060 average 0.005

TII CKD LS 10% 1 0.0060

TII CKD LS 10% 2 0.0050

TII CKD LS 10% 3 0.0050

TII CKD LS 10% 4 0.0060 average 0.005

TII CKD SLX 10% 1 0.0080

TII CKD SLX 10% 2 0.0070

TII CKD SLX 10% 3 0.0080

TII CKD SLX 10% 4 0.0070 average 0.008

TII CKD A 10% 1 0.0140

TII CKD A 10% 2 0.0140

TII CKD A 10% 3 0.0150

TII CKD A 10% 4 0.0150 average 0.015

TII CKD B 10% 1 0.0110

TII CKD B 10% 2 0.0110

TII CKD B 10% 3 0.0100

TII CKD B 10% 4 0.0120 average 0.011

TII CKD C 10% 1 0.0120

TII CKD C 10% 2 0.0120

TII CKD C 10% 3 0.0110

TII CKD C 10% 4 0.0110 average 0.012

TII CKD D 10% 1 0.0170

TII CKD D 10% 2 0.0170

TII CKD D 10% 3 0.0190

TII CKD D 10% 4 0.0160 average 0.017

TII CKD E 10% 1 0.0210

TII CKD E 10% 2 0.0230

TII CKD E 10% 3 0.0210

TII CKD E 10% 4 0.0220 average 0.022

TII CKD F 10% 1 0.0190

TII CKD F 10% 2 0.0170

TII CKD F 10% 3 0.0180

TII CKD F 10% 4 0.0180 average 0.018

TII CKD LS 20% 1 0.0050

TII CKD LS 20% 2 0.0060

TII CKD LS 20% 3 0.0050

TII CKD LS 20% 4 0.0050 average 0.005

TII CKD SLX 20% 1 0.0050

TII CKD SLX 20% 2 0.0060

TII CKD SLX 20% 3 0.0060

TII CKD SLX 20% 4 0.0060 average 0.006

TII CKD A 20% 1 0.0150

TII CKD A 20% 2 0.0150

TII CKD A 20% 3 0.0140

TII CKD A 20% 4 0.0150 average 0.015

TII CKD B 20% 1 0.0130

TII CKD B 20% 2 0.0130

TII CKD B 20% 3 0.0120

TII CKD B 20% 4 0.0110 average 0.012

TII CKD C 20% 1 0.0140

TII CKD C 20% 2 0.0140

TII CKD C 20% 3 0.0160

TII CKD C 20% 4 0.0150 average 0.015

TII CKD D 20% 1 0.0490

TII CKD D 20% 2 0.0470

TII CKD D 20% 3 0.0490

TII CKD D 20% 4 0.0500 average 0.049

TII CKD E 20% 1 0.0550

TII CKD E 20% 2 0.0530

TII CKD E 20% 3 0.0520

TII CKD E 20% 4 0.0530 average 0.053

TII CKD F 20% 1 0.0280

TII CKD F 20% 2 0.0290

TII CKD F 20% 3 0.0290

TII CKD F 20% 4 0.0290 average 0.029

323


0

0.01

0.02

0.03

0.04

0.05

0.06

14d

TII

TII C

KD

A 1

0%

TII C

KD

A 2

0%

TII C

KD

B 1

0%

TII C

KD

B 2

0%

TII C

KD

C 1

0%

TII C

KD

C 2

0%

TII C

KD

D 1

0%

TII C

KD

D 2

0%

TII C

KD

E 1

0%

TII C

KD

E 2

0%

TII C

KD

F 1

0%

TII C

KD

F 2

0%

TII C

KD

LS

10%

TII C

KD

LS

20%

TII C

KD

SLX

10%

TII C

KD

SLX

20%

TII Blends


Analysis of Variance Source DF Sum of Squares Mean Square F Ratio Prob > F TII Blends 16 0.01318511 0.000824 915.6327 <.0001 Error 55 0.00004950 9e-7 C. Total 71 0.01323461


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Characterization and Utilization of Cement Kiln Dusts ... · PDF fileii Characterization and Utilization of Cement Kiln Dusts (CKDs) as Partial Replacements of Portland Cement Doctor