UNIVERSITI PUTRA MALAYSIA

NIMA FARZADNIA

FK 2014 87

EFFECTS OF NANOMATERIALS ON HIGH PERFORMANCE CONCRETE MORTARS EXPOSED TO ELEVATED

TEMPERATURES

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CONCRETE MORTARS EXPOSED TO ELEVATEDTEMPERATURES

By

NIMA FARZADNIA

Thesis Submitted to the School of Graduate Studies, Universiti PutraMalaysia, in Fulfilment of the Requirements for the Degree of Doctor

of Philosophy

May 2014

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DEDICATIONS

I dedicate this dissertation to all of the inspiring people who have enlightened

not only my life but the life of others by unselfishly dedicating themselves to

share love, knowledge and experience.

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Abstract of thesis presented to the Senate of Universiti Putra Malaysia infulfilment of the requirement for the degree of Doctor of philosophy.

EFFECTS OF NANOMATERIALS ON HIGH PERFORMANCECONCRETE MORTARS EXPOSED TO ELEVATED

TEMPERATURES

By

NIMA FARZADNIA

May 2014

Chair: Professor Dato Ir. Abang Abdullah Abang Ali

Faculty: Engineering

High performance concrete (HPC) is currently used in massive amounts in theconstruction industry due to its technical and economical advantages over nor-mal concrete. The HPC is characterized by improved mechanical and durabilityproperties resulting from the use of chemical and mineral admixtures as well asspecialized production processes. However, sharp strength loss and reduction inelastic modulus at temperatures below 400 ◦C are major disadvantages of HPCcompared to normal concrete; raising questions on its application in the construc-tion industry at high temperatures. The demerit of HPC at elevated temperaturesup to 400 ◦C is mostly attributed to a mechanism called hydrothermal process bywhich cracks and in some cases spalling occur due to vapor pressure. It is causedby the release of water from capillaries as well as degradation of hydration productsentrapped in the impermeable microstructure of the HPC, increasing the internalvapor pressure. All this is brought about by the low water to binder ratio in theHPC with the presence of mineral admixtures such as silica fume. Nonetheless,some studies have mentioned the positive effect of mineral admixtures at elevatedtemperatures due to the formation of stronger clusters of calcium silicate hydrateand restriction in crystal growth of calcium hydroxide.

This study investigated the behavior of high performance concrete mortars withnanomaterials at elevated temperatures to simulate the behavior of binding ma-trix exposed to heat in order to increase the heat resistant behavior of the bindingmatrix with a focus on temperatures below 400 ◦C. Furthermore, since there is a

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debate on the effects of mineral admixtures on the HPC at elevated temperatures,the findings of this study helps to identify the critical influencing factors namely:chemical composition, moisture content, and permeability in behavior of the bind-ing matrix at elevated temperatures. It is well established that nanomaterials canmodify the above mentioned factors due to their size, shape, and solid state.

Four nanomaterials, namely: nano silica with amorphous state, nano titania withboth amorphous and crystal states, nano alumina with pure crystal state, andhalloysite nano clay with tubular shape were chosen for this study and fractionsof 1, 2 and 3% by weight of cement were added to the mixes. XRD, DSC, SEMand gas permeability tests were conducted to investigate the chemical compositionand microstructural changes of the HPC mortars after being exposed to elevatedtemperatures up to 1000 ◦C. The residual compressive strength, energy absorp-tion, brittleness index and relative elastic modulus were studied to compare themechanical properties of mortars with and without nanomaterials and to identifythe most effective amount of each nanomaterials. Addition of a 1% nano silica,2% nano titania, 1% nano alumina, and 3% halloysite nano clay , as most effec-tive amounts, enhanced the heat resistant behavior of the mortars up to 400 ◦Cin terms of residual mechanical properties and the microstructure. Up to 13%enhancement in the relative residual compressive strength, 28% enhancement inthe relative elastic modulus, and 32% enhancement in the permeability of mortarswere achieved when nanomaterials were added. The interlocking and filling effectsof the nanomaterials played an important role in controlling the governing factorof vapor pressure in the binding matrix.

Keywords: High performance concrete mortars, Elevated temperatures, nano-materials, Mechanical properties, Chemical composition.

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Abstrak tesis yang dikemukakan kepada Senat Universiti Putra Malaysia sebagaimemenuhi keperluan untuk ijazah Doktor Falsafah

KESAN BAHAN NANO KE ATAS MORTAR KONKRITBERPRESTASI TINGGI TERDEDAH PADA SUHU MENINGKAT

Oleh

NIMA FARZADNIA

Mei 2014

Pengerusi: Professor Dato Ir. Abang Abdullah Abang Ali

Fakulti: Kejuruteraan

Konkrit prestasi tinggi (HPC) digunakan dalam jumlah yang besar dalam indus-tri pembinaan pada masa kini disebabkan kelebihannya dari segi teknikal danjuga ekonomi berbanding konkrit normal. Peningkatan ciri mekanikal dan ke-tahanlasakan HPC terhasil daripada penggunaan bahan tambah kimia dan min-eral serta proses penghasilan yang khusus. Walaubagaimanapun, kehilangan de-ripada kekuatan yang mendadak dan pengurangan modulus kenyal pada suhukurang 400 ◦C adalah kelemahan utama HPC berbanding konkrit normal; rintan-gan haba ini menambahkan persoalan terhadap penggunaannya di dalam industripembinaan. Kelemahan HPC pada suhu meningkat sehingga 400 ◦C kebanyakan-nya diperolehi daripada mekanisma yang dipanggil proses hidrotermal dimana re-takan dan di dalam beberapa kes serpihan berlaku disebabkan tekanan wap. Inidisebabkan oleh air yang dibebaskan daripada rerambut serta penurunan produkpenghidratan yang terperangkap di dalam mikrostruktur tidak boleh telap HPCdan meningkatkan tekanan wap dalaman. Semua ini disebabkan oleh nisbah airkepada pengikat yang rendah di dalam HPC dengan kehadiran bahan tambah min-eral seperti wasap silika. Namun begitu, beberapa kajian ada menyatakan tentangkesan positif bahan tambah mineral pada suhu meningkat disebabkan oleh pem-bentukan kelompok kalsium silikat hidrat yang lebih kuat dan pembatasan dalamtumbesaran hablur kalsium hidroksida.

Kajian ini tertumpu kepada kelakuan mortar konkrit prestasi tinggi dengan bahannano pada suhu meningkat untuk mensimulasi kelakuan pengikatan matriks yangdidedahkan kepada haba bertujuan untuk meningkatkan kelakuan rintangan habapengikatan matriks dengan fokus pada suhu kurang daripada 400 ◦C. Tambahan

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pula, kerana wujudnya perdebatan terhadap kesan bahan tambah mineral ter-hadap HPC pada suhu meningkat, penemuan kajian ini dapat membantu dalammengenalpasti faktor kritikal yang mempengaruhi iaitu: komposisi kimia, kan-dungan lembapan, dan kebolehtelapan dalam kelakuan pengikatan matriks padasuhu meningkat. Adalah diketahui bahawa bahan nano dapat mengubahsuai fak-tor yang disebutkan di atas disebabkan saiz, bentuk dan keadaan pepejal bahantersebut.

Empat bahan nano yang biasa digunakan iaitu: silika nano dengan keadaan amor-fus, titania nano dengan keadaan amorfus dan juga hablur, alumina nano den-gan keadaan hablur tulen, dan tanah liat nano haloisit berbentuk tiub dipilihuntuk kajian ini dan pecahan 1, 2 dan 3% dari berat simen telah ditambah kedalam campuran. Ujian XRD, DSC, SEM dan kebolehtelapan telah dijalankanuntuk mengkaji komposisi kimia dan perubahan mikrostruktur HPC mortar se-lepas didedahkan kepada suhu meningkat sehingga 1000 ◦C. Baki kekuatan mam-pat, serapan tenaga, indeks kerapuhan dan nisbi modulus kenyal dikaji untukdibandingkan dengan ciri mekanikal mortar dengan dan tanpa bahan nano untukmengenalpasti jumlah paling berkesan untuk setiap jenis bahan nano. Penamba-han 1% silika nano, 2% titania nano, 1% alumina nano dan 3% tanah liat nanohaloisit adalah jumlah paling berkesan untuk meningkatkan kelakuan rintanganhaba mortar hingga 400 ◦C dalam sebutan ciri mekanikal dan mikrostruktur. Se-hingga 13% peningkatan dalam nisbi baki kekuatan mampat, 28% peningkatandalam nisbi modulus kenyal, dan 32% peningkatan dalam kebolehtelapan mor-tar berjaya dicapai apabila bahan nano ditambah. Kesan saling mengunci danisian oleh bahan nano memainkan peranan paling penting untuk mengawal faktorpengawal tekanan wap dalam matriks pengikat.

Kata kunci: Mortar konkrit prestasi tinggi, Suhu meningkat, Bahan nano, Cirimekanikal, Komposisi kimia.

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ACKNOWLEDGEMENTS

I would never have been able to finish my dissertation without the guidance ofmy committee members, help from friends, and support from my family. I wouldlike to express my deepest gratitude to my supervisor, Prof. Dato Ir. Abang,for his excellent guidance, caring, patience, and providing me with an excellentatmosphere for doing research. I would like to thank Prof. Ramazan, for guidingmy research for the past four years and helping me to develop my backgroundin material science. I would also like to thank Dr. Anwar, who provided mewith the opportunity to experience some part of the research at The university ofNottingham. I would also like to express the deepest appreciation to HRC staff;Mrs. Erna, Mrs. Anna, Miss Liyana, and Mrs. Lela who assisted me sincerely infulfilling my education goals. Many thanks go to Mr Fairus and other techniciansin the material laboratory of Universiti Putra Malaysia for helping me in my datacollection. My research would not have been possible without their helps. Finally,I would like to offer my special thanks to Mr Iraj Toloue who helped me edit mythesis.

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I certify that a Thesis Examination Committee has met on (30 May 2014) toconduct the final examination of (NIMA FARZADNIA) on his (or her) the-sis entitled “EFEFCTS OF NANO MATERIALS IN HIGH PERFOR-MANCE CONCRETE MORTARS EXPOSED TO ELEVATED TEM-PERATURES” in accordance with the Universities and University Colleges Act1971 and the Constitution of the Universiti Putra Malaysia [P.U.(A) 106] 15 March1998. The Committee recommends that the student be awarded the (Doctor ofphilosophy).

Members of the Thesis Examination Committee were as follows:

Law Teik Hua , PhDAssociate ProfessorFaculty of EngineeringUniversiti Putra Malaysia(Chairperson)

Ratnasamy a/l Muniandy , Ph.D.ProfessorFaculty of EngineeringUniversiti Putra Malaysia(Internal Examiner)

Mohd Saleh b Jaafar, Ph.D.ProfessorMohd Saleh b JaafarUniversiti Putra Malaysia(Internal Examiner)

Abdurrahman Guner, Ph.D.ProfessorAbdurrahman GunerIstanbul UniversityTurkey(External Examiner)

BUJANG KIM HUAT, Ph.D.Professor and Deputy DeanSchool of Graduate StudiesUniversiti Putra Malaysia

Date:

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This thesis was submitted to the Senate of Universiti Putra Malaysia and has beenaccepted as fulfilment of the requirement for the degree of Doctor of philosophy.

The members of the Supervisory Committee were as follows:

Abang Abdullah Abang AliProfessorFaculty of EngineeringUniversiti Putra Malaysia(Chairperson)

Ramazan Demirboga, PhDAssociate ProfessorFaculty of EngineeringUniversiti Putra Malaysia(Member)

Farah Nora Azienta bt. Abd. Aziz, PhDSenior lecturerFaculty of EngineeringUniversiti Putra Malaysia(Member)

Mohammad Parvez Anwar, PhDAssistant ProfessorFaculty of EngineeringThe University of Nottingham(Member)

BUJANG BIN KIM HUAT, PhDProfessor and DeanSchool of Graduate StudiesUniversiti Putra Malaysia

Date:

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DECLARATION

Declaration by graduate student

I hereby confirm that:

• this thesis is my original work;

• quotations, illustrations, and citations have been duly referenced;

• this thesis has not been submitted previously or concurrently for any otherdegree at any other institutions;

• intellectual property from thesis and copyright of thesis are fully-owned byUniversiti Putra Malaysia (Research) Rules 2012;

• written permission must be obtained from supervisor and the office of DeputyVice-Chancellor (Research and Innovation) before thesis is published (in theform of written, printed or in electronic form) including books, journals, mod-ules, proceedings, popular writings, seminar papers, manuscripts, posters,lecture notes, learning modules or any other materials as stated in the Uni-versiti Putra Malaysia (Research) Rules 2012;

• there is no plagiarism or data falsification/fabrication in the thesis, andscholary integrity is upheld as according to the University Putra Malaysia(Graduate Studies) Rules 2003 (Revision 2012-2013) and the Universiti Pu-tra Malaysia (Research) Rules 2012. The thesis has undergone plagiarismdetection software.

Signature: Date: 18-7-2014

Name and Matric NO.: Nima Farzadnia (GS25991)

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Declaration by Members of Supervisory Committee

This is to confirm that:

• the research conducted and the writing of this thesis was under our supervi-sion;

• supervision responsibilities as stated in the Universiti Putra Malaysia (Grad-uate Studies) Rules 2003 (Revision 2012-2013) are adhered to.

Signature: Signature:Name of Name ofChairman of Member ofSupervisory SupervisoryCommittee: Committee:

Signature: Signature:Name of Name ofMember of Member ofSupervisory SupervisoryCommittee: Committee:

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TABLE OF CONTENTS

Page

DEDICATIONS i

ABSTRACT ii

ABSTRAK iv

ACKNOWLEDGEMENTS vi

APPROVAL vii

DECLARATION ix

LIST OF TABLES xiv

LIST OF FIGURES xv

CHAPTER

1 INTRODUCTION 1

1.1 Background 11.2 Statement of the Problem 21.3 Objectives 21.4 Research Questions 31.5 Significance of the Study 31.6 Scope of Research 31.7 Overview of the Thesis 4

2 LITERATURE REVIEW 7

2.1 Introduction 72.2 High Performance Concrete 7

2.2.1 Definition, Constituents and Properties 72.2.2 Factors Influencing Properties of HPC 8

2.3 Concrete at Elevated Temperatures 112.3.1 Effects of Elevated Temperatures on Chemical and Microstruc-

tural Properties of Concrete 122.3.2 Effects of Elevated Temperature on Mechanical Properties

of Concrete 162.3.3 Influencing Factors on the Behavior of Concrete at Elevated

Temperatures 202.3.4 Different Behavior of High Performance Concrete at Ele-

vated Temperatures 212.3.5 Modification of the Matrix to Enhance its Heat Resistance 26

2.4 Nanomaterials 28

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2.4.1 Definition 282.4.2 Incorporation of Nano Silica in Cementitous Composites 292.4.3 Incorporation of Nano Titania in Cementitous Composites 332.4.4 Incorporation of Nano Alumina in Cementitous Composites 372.4.5 Incorporation of Nano Clay in Cementitous Composites 38

2.5 Conclusion 40

3 METHODOLOGY 43

3.1 Introduction 433.2 Materials 45

3.2.1 Constant Constituents of Mortars 453.2.2 Nanomaterials 47

3.3 Laboratory Work 503.3.1 Safety Equipments 503.3.2 Aggregate Preparation and Tests 513.3.3 Mortar Preparation 543.3.4 Exposure to Elevated Temperatures 58

3.4 Testing 603.4.1 Compressive Test 603.4.2 Ultra Sonic Pulse Velocity 633.4.3 Mass Loss 633.4.4 X Ray Diffractometer (XRD) 643.4.5 Scanning Electron Microscope (SEM) 653.4.6 Differential Scanning Calorimeter (DSC) 683.4.7 Gas Permeability 68

4 RESULTS AND DISCUSSION 73

4.1 Introduction 734.2 Characterization of Halloysite Nano Clay Mortars at Different Tem-

peratures 734.2.1 Chemical Composition and Microstructural Changes 744.2.2 Mechanical Properties 82

4.3 Characterization of Nano Silica Mortars at Different Temperatures 884.3.1 Chemical composition and microstructure 884.3.2 Mechanical Properties 95

4.4 Characterization of Nano Titania Samples at Different Temperatures1024.4.1 Chemical Composition and Microstructure 1034.4.2 Mechanical Properties 110

4.5 Characterization of Nano Alumina Samples at Different Temperatures1174.5.1 Chemical Composition and Microstructure 1184.5.2 Mechanical Properties 125

4.6 Evaluations and Comparisons 133

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4.6.1 Residual Mechanical Properties of Mortars with Sphericalnanomaterials 133

4.6.2 Critical factors on Behavior of the Binding Matrix in HighPerformance Concrete Mortars at Elevated Temperatures 138

5 CONCLUSION AND RECOMMENDATION FOR FUTURE RE-

SEARCH 1515.1 Introduction 1515.2 Highlighted Concluding Remarks 1525.3 Comparisons 1555.4 Detailed Concluding Remarks 156

5.4.1 Halloysite Nano Clay (HNT) 1565.4.2 Nano Silica 1575.4.3 Nano Titania 1595.4.4 Nano Alumina 160

5.5 Recommendation for Future Research 161

REFERENCES/BIBLIOGRAPHY 162

BIODATA OF STUDENT 178

LIST OF PUBLICATIONS 179

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LIST OF TABLES

Table Page

2.1 Critical points on the curve (ASTM E119, 1995) 122.2 Mineralogical and strength changes to concrete caused by heating

(Ingham, 2009) 202.3 Effect of different factors on behavior of concrete at elevated tem-

peratures 21

3.1 Chemical properties of Portland cement type I and silica fume 463.2 Aggregate grading 463.3 Physical properties of nano silica (Provided by the supplier) 483.4 Physical properties of nano titania (Provided by the supplier) 483.5 Physical properties of nano alumina (Provided by the supplier) 493.6 Physical properties of halloysite nano clay (Provided by the sup-

plier) 503.7 Mix proportion 553.8 The dry mixes composition of blended cement (mass%) 55

4.1 Physical properties of nanomaterials 1334.2 CH intensity of NS1, NT2, NA1, and Control samples at room tem-

perature, 400, and 800 ◦C 142

5.1 Comparison of results 156

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LIST OF FIGURES

Figure Page

2.1 Microstructure of a HPC: low porosity and homogeneity of the ma-trix: (a) absence of transition zone between the aggregate and ce-ment paste; (b) dense cement paste in an air entrained high perfor-mance concrete (Aitcin, 2003) 10

2.2 Microstructure of high water/cement ratio concrete: (a) high poros-ity and heterogeneity of the matrix, (b) orientated crystal of Ca(OH) 2 on aggregate (AG) , (c) CH crystals (Aitcin, 2003) 10

2.3 Time - Temperature curve (ASTM E119, 1995) 112.4 Cement matrix in the interfacial transition zone at 20 ◦C, 350 ◦C

and 550 ◦C (Annerel and Taerwe, 2009) 132.5 X-ray diffractograms of mortar samples of concrete monitoring Ca

(OH)2 fired at different temperature regimes: (a) core, (b) surface(Handoo et al., 2002) 14

2.6 X-ray diffractograms of mortar samples of concrete monitoring CaCO3fired at different temperature regimes: (a) core, (b) surface (Handooet al., 2002) 15

2.7 Visual evidence of temperature to which concrete has been heated(Georgali and Tsakiridis, 2005) 15

2.8 Development of cracks around the aggregates and in the cementmatrix (Annerel and Taerwe, 2009) 16

2.9 Compressive strength of Normal Strength Concrete (NSC) , HighPerformance Concrete (HPC) , High Strength Concrete (HSC) afterhigh temperature (Xiao and Konig, 2004) 17

2.10 Mechanical behavior of Normal Strength Concrete (NSC) and steelfiber concrete (SFC) after high temperature (Xiao and Konig, 2004) 17

2.11 Modulus of elasticity of Normal Strength Concrete (NSC) and HighPerformance Concrete (HPC) after high temperature (Xiao andKonig, 2004) 17

2.12 Surface cracking after elevating 200 ◦C holding 60 minute (Wanget al., 2005) 18

2.13 microstructural changes of concrete at 20 ◦C, 350 ◦C and 550 ◦C.(A: aggregate, C: cement) (Annerel and Taerwe, 2009) 19

2.14 Representation of spalling in concrete samples at elevated temper-atures (Morais et al., 2010) 22

2.15 Residual compressive strengths of HSC and normal concrete at dif-ferent temperatures (Phan and Carino, 1998) 23

2.16 Cracking and moisture marks on the lateral face of sample (Min-deguia et al., 2010) 24

2.17 Residual compressive strength of HSCs and NSCs (Poon et al., 2001) 252.18 Particle size and specific surface area related to concrete materials

(Sobolev, 2005) 28

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2.19 TEM image (a) and EDS profile (b) of nano silica particles (Berraet al., 2012) 30

2.20 X-ray diffraction analysis of nano-SiO2 (Kontoleontos et al., 2012) 302.21 Influence of nS (wt%) content on temperature of cement paste hy-

dration (Senff et al., 2009) 312.22 SEM images of the ITZ in the mortar with (Right) and without

(Left) nano silica (1.0%) addition (Konig et al., 2012) 332.23 X-ray diffraction curve of nano-TiO2 (Meng et al., 2012) 342.24 SEM photo of nano-TiO2 (Meng et al., 2012) 342.25 Visual representation of hydration with presence of nano titania

(Lee et al., 2010) 352.26 rate of heat evolution in samples with (a) P 25 and (b) Anatase

comparing samples without nano TiO2 (Chen, et al., 2012) 362.27 XRD pattern (Left) (Tok et al., 2006) and TEM image (Right) of

nano alumina (Nazari and Riahi 2011a) 372.28 SEM images of microstructure mortars as 28 days with 5% (Right)

and with 0% (Left) nano alumina (Li et al., 2006) 382.29 TEM images of nano metakaolin (Left) (Morsy et al., 2010) and

nano montmorillonite (Right) (Chang et al., 2007) 392.30 XRD pattern of nano montmorillonite (Chang et al., 2007) 392.31 SEM images of microstructure of hydrated mortars at 28 day. With-

out nano clay (Left) and with 4% nano clay (Right) (Morsy et al.,2010) 40

3.1 The conceptual frameworks a)to identify optimum amounts of eachnanomaterials b) to identify critical factors on behavior of the bind-ing matrix at elevated temperatures 44

3.2 Methodology flowchart 453.3 Accumulative percent passing of aggregates 473.4 nanomaterials 473.5 XRD pattern of nano silica (provided by the supplier) 483.6 XRD pattern of nano titania 493.7 TEM image of halloysite nano clay (provided by the supplier) 503.8 safety equipments 513.9 Aggregate preparation; washing 513.10 Aggregate preparation; drying 523.11 Aggregate preparation; sieving and grading 523.12 Aggregate preparation; storing 523.13 Aggregate preparation; SSD testing 533.14 Aggregate preparation; oven drying 533.15 Aggregate preparation; relative density test 533.16 Scaling nanomaterials with high accuracy balance 553.17 Mixing powder material with water and SP, using a mixer 563.18 Equipments for flowability test 563.19 Flowability test 56

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3.20 Measurement of mortar flow 573.21 Metal and plastic molds for compression and permeability test, re-

spectively 573.22 Air pressure cleaning and lubrication of molds 573.23 fresh mortar molded for 24 hours 583.24 Lime saturated water curing with temperature control 583.25 Electric furnace and arrangement of samples 593.26 Time - Temperature curve 593.27 Samples after exposure to 1000 ◦C 603.28 Servons System Daventry machine 613.29 Sample placing in the compression test machine 613.30 Test sample before and after compressive test 623.31 Data analysis (Stress- Strain curves) 623.32 UPV apparatus 633.33 sampling for XRD test 643.34 Shimadtzu X Ray diffractometer 653.35 Gold coating of samples using Emitech K550X Sputter Coater 663.36 Representation of samples before and after coating 663.37 Thermo Scientific NORAN System 7 X-ray Microanalysis System 673.38 Adjustment of samples in the machine 673.39 SEM image processing 683.40 Mettler Toledo DSC823e 683.41 Schematic drawing of gas permeability measurement apparatus (Taghi-

yari, 2011) 693.42 Permeability apparatus 703.43 Sealing the samples 713.44 Gas permeability test procedure 71

4.1 XRD patterns of Control and NC2 at room temperature at 28 days 744.2 XRD patterns of Control, NC1, NC2 and NC3 at 400 ◦C 754.3 XRD patterns of Control, NC1, NC2 and NC3 at 800 ◦C 764.4 DSC Thermograms of control and NC2 samples at 28 days 764.5 Mass losses of NC1, NC2, NC3 and Control samples at elevated

temperatures 774.6 SEM images of a) Control, b) NC1, c) NC2 and d) NC3 at room

temperature at 28 days 784.7 The interlocking effect of halloysite nano clay 784.8 SEM images of a) Control, b) NC1, c) NC2 and d) NC3 at 400 ◦C 794.9 SEM images of a) Control, b) NC1, c) NC2 and d) NC3 at 800 ◦C

(10 micron) 804.10 SEM images of a) Control, b) NC1, c) NC2 and d) NC3 at 800 ◦C

(50 micron) 804.11 Permeability coefficients of NC1, NC2, NC3, and Control samples

at 28 ◦C, 300 ◦C and 600 ◦C 81

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4.12 Enhancement of Compressive strength by incorporation of 1, 2, and3% HNT at 28 days 82

4.13 Relative compressive strengths of NC1, NC2, and NC3, and Controlat different temperatures 83

4.14 a) pulse velocity of samples with and without nano alumina at dif-ferent temperatures. b) Relationship between relative compressivestrength and relative pulse 84

4.15 Stress -Strain curve of Control, NC1, NC2 and NC3 at differenttemperatures 86

4.16 Relative elastic modulus of NC1, NC2 and NC3 and Control samplesat elevated temperatures 87

4.17 Brittleness indexes of NC1, NC2, NC3 and control samples at dif-ferent temperatures 88

4.18 XRD patterns of NS1 and Control samples at room temperature at28 days 89

4.19 XRD patterns of Control samples, NS1, NS2 and NS3 at 400 ◦C 904.20 XRD patterns of Control samples, NS1, NS2 and NS3 at 800 ◦C 904.21 DSC diagrams peaks of Control samples, NS1, NS2 and NS3 914.22 Mass losses of NS1, NS2, NS3 and Control samples at elevated tem-

peratures 924.23 SEM images of a) Control sample and b) NS1 at room temperature

at 28 days 924.24 SEM images of a) Control samples at 400 ◦C (a.1) and 800 ◦C (a.2).

b) NS1 at 400 ◦C (b.1) and 800 ◦C (b.2). c) NS2 at 400 ◦C (c.1) and800 ◦C (c.2). d) NS3 at 400 ◦C (d.1) and 800 ◦C (d.2) 93

4.25 Permeability coefficients of NS1, NS2, NS3, and Control samples at28 ◦C, 300 ◦C and 600 ◦C 95

4.26 Residual compressive strengths of NS1, NS2, NS3 and Control sam-ples at different temperatures 96

4.27 Relative residual strengths of NS1, NS2, NS3, and Control samplesat different temperatures 97

4.28 a) Pulse velocity of samples with and without nano silica at ele-vated temperatures. b) Relationship between relative compressivestrength and relative pulse velocity for samples with and withoutnano silica at elevated temperatures 98

4.29 Stress-strain curves of NS1, NS2, NS3 and Control samples at 28 ◦C,100 ◦C,200 ◦C, 300 ◦C, 400 ◦C, 600 ◦C, 800 ◦C and 1000 ◦C 100

4.30 Relative elastic modulus of NS1, NS2, NS3 and Control samples atelevated temperatures 101

4.31 Brittleness indexes of NS1, NS2, NS3 and Control samples at ele-vated temperatures 102

4.32 XRD patterns of NT2 and Control samples at room temperature at28 days 103

4.33 XRD patterns of NT1, NT2, NT3 and Control samples at 400 ◦C 1044.34 XRD patterns of NT1, NT2, NT3 and Control samples at 800 ◦C 104

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4.35 DSC diagrams peaks of Control samples, NT1, NT2 and NT3 1054.36 Mass losses of NT1, NT2, NT3 and Control samples at elevated

temperatures 1064.37 SEM images of a) Control sample and b) NT2 at room temperature

at 28 days 1074.38 SEM images of a) Control samples at 400 ◦C (a.1) and 800 ◦C (a.2).

b) NT1 at 400 ◦C (b.1) and 800 ◦C (b.2). c) NT2 at 400 ◦C (c.1)and 800 ◦C (c.2). d) NT3 at 400 ◦C (d.1) and 800 ◦C (d.2) 108

4.39 Permeability coefficients of NT1, NT2, NT3 and Control samplesat 28 ◦C, 300 ◦C and 600 ◦C 109

4.40 Residual compressive strengths of NT1, NT2, NT3 and Control sam-ples at different temperatures 111

4.41 The relative residual strength of NT1, NT2, NT3, and Control sam-ples at different temperatures 112

4.42 a) Pulse velocity of samples with and without nano titania at ele-vated temperatures. b) Relationship between relative compressivestrength and relative pulse velocity for samples with and withoutnano titania at elevated temperatures 113

4.43 Stress-strain curves of NT1, NT2, NT3 and Control samples at28 ◦C,100 ◦C, 200 ◦C, 400 ◦C, 600 ◦C, 800 ◦C and 1000 ◦C 114

4.44 Relative elastic modulus of NT1, NT2, NT3 and Control samplesat elevated temperatures 115

4.45 Brittleness indexes of NT1, NT2, NT3 and Control samples at ele-vated temperatures 117

4.46 XRD patterns of NA1 and Control samples at room temperature at28 days 118

4.47 XRD patterns of NA1, NA2, NA3, and Control samples at 400 ◦C 1194.48 XRD patterns of NA1, NA2, NA3, and control samples at 800 ◦C 1204.49 Formation of Mullite at 800 ◦C in the binding matrix with the pres-

ence of nano alumina 1204.50 DSC diagrams of NA1, NA2, NA3, and Control samples at 28 days 1214.51 Mass losses of NA1, NA2, NA3 and Control samples at elevated

temperatures 1224.52 SEM images of a) Control sample and b) NA1 at room temperature

at 28 days 1234.53 SEM images of a) Control b) NA1 c) NA2 d) NA3 400 ◦C 1234.54 SEM images of a) Control b) NA1 c) NA2 d) NA3 at 800 ◦C 1244.55 Permeability coefficients of NA1, NA2, NA3 and Control samples

at 28 ◦C, 300 ◦C and 600 ◦C 1254.56 Compressive strengths of NA1, NA2, NA3 and Control samples at

different temperatures 1264.57 The relative residual compressive strength of NA1, NA2, NA3, and

Control samples at different temperatures 127

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4.58 a) Pulse velocity of samples with and without nano alumina at el-evated temperatures. b) Relationship between relative compressivestrength and relative pulse velocity for samples with and withoutnano alumina at elevated temperatures 128

4.59 Stress-strain curves of NA1, NA2, NA3 and Control samples at28 ◦C, 100 ◦C, 200 ◦C, 300 ◦C, 400 ◦C, 600 ◦C, 800 ◦C and 1000 ◦C 129

4.60 Relative elastic modulus of NA1, NA2, NA3 and Control samplesat elevated temperatures 131

4.61 Brittleness indexes of NA1, NA2, NA3 and Control samples at ele-vated temperatures 132

4.62 Residual compressive strengths of NS1, NT2, NA1 and control sam-ples at different temperatures 133

4.63 Stress - strain curves of NS1, NT2, NA1 and control samples atdifferent temperatures 136

4.64 Brittleness indexes of NS1, NT2, NA1 and control samples at dif-ferent temperatures 137

4.65 Relative residual comparative strengths of mortars at elevated tem-peratures 137

4.66 Relative residual comparative strengths of mortars at elevated tem-peratures 138

4.67 Moisture contents of Control, NS1, NT2, and NA1 samples beforeheat exposure 139

4.68 Mass losses of NS1, NT2, NA1 and control samples at differenttemperatures 139

4.69 XRD patterns for Control, NS1, NT2 and NA1 samples at roomtemperature 142

4.70 XRD patterns of control, NS1, NT2 and NA1 at 400 ◦C 1444.71 DSC endothermic peaks related to control, NS1, NT2 and NA1 1444.72 XRD patterns of control, NS1, NT2 and NA1 at 800 ◦C 1454.73 SEM images of a) control b) NS1 c) NT2 and d) NA1 at 28 days at

room temperature 1464.74 SEM images of a) Control samples at 400 ◦C (a.1) and 800 ◦C (a.2).

b) NS1 at 400 ◦C (b.1) and 800 ◦C (b.2). c) NT2 at 400 ◦C (c.1)and 800 ◦C (c.2). d) NA1 at 400 ◦C (d.1) and 800 ◦C (d.2) 147

4.75 Permeability coefficient s of control, NS1, NT2 and NA1 samples atdifferent temperatures 148

5.1 The enhancement of nanomaterial mortars comparing the controlsamples in terms of permeability 153

5.2 The enhancement of nanomaterial samples comparing control sam-ples in terms of compressive strength at room temperature 153

5.3 The enhancement of nanomaterial mortars comparing the controlsamples in terms of compressive strength 154

5.4 The enhancement of nanomaterial mortars comparing the controlsamples in terms of elastic modulus 154

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CHAPTER 1

INTRODUCTION

1.1 Background

Concrete is a widely used construction material around the world and its prop-erties have undergone changes through technological advancements. Numeroustypes of concrete have been developed to enhance its properties. Currently, high-performance concrete (HPC) is used in massive amounts due to its technical andeconomical advantages over normal concrete.The HPC is characterized by im-proved mechanical and durability properties resulting from the use of chemicaland mineral admixtures as well as specialized production processes.

New technologies may bring new problems in some applications and should bestudied carefully before being applied practically in industry. One important pre-caution to take into consideration is when high temperatures are involved. Normalconcrete meets certain minimum safety standards since it limits the extension ofdamage in fire due to its heat resistance. Recently, drawbacks in the HPC have at-tracted the attention of researchers after some real vehicle accident fire exposuressuch as at the Great Belt tunnel in Denmark and the Chunnel tunnel. A sharpstrength loss and in some cases explosive spalling were some of the major disad-vantages of the HPC at elevated temperatures raising questions on its applicationin the construction industry, especially in tunnels, power plants and military build-ings. Furthermore, concrete is used in some heat exposed environments such asrunway areas, air field pavements, molten metal splash areas, hot material storageareas, fire resistant plastering works and some other possible applications whichnecessitate a further study on processes by which heat resistance is enhanced.

Some of the most important factors affecting the resistance of concrete at ele-vated temperatures are aggregate type, cement type, and water to binder ratio. Anumber of studies have investigated the effect of the above-mentioned factors onthe behavior of both normal concrete and HPC.For the HPC and its behavior atelevated temperatures, researchers attach great importance to the effect of min-eral admixtures since they are the main distinguishing constituents of HPC fromconventional concrete.

Mineral admixtures are available in the market as industrial by-products suchas silica fume and fly ash or agro-wastes such as rice husk and palm oil fuel ash.They modify the binding matrix of concrete and the interfacial transition zone(ITZ) by their effect on the formation of hydration products through their poz-zolanic behavior and nucleation effect due to their high surface area. Today, anumber of efforts have been made to study the addition of mineral additives intothe binding matrix in order to reduce consumption of cement as well as to enhancethe properties of concrete.

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1.2 Statement of the Problem

Results from the latest studies on mineral admixtures in the HPC at elevatedtemperatures have encouraged discussions on their effect on the behavior of HPCbinding matrix at elevated temperatures. A number of researchers have addressedthe adverse effect of incorporation of mineral admixtures, which resulted in highimpermeability of the binding matrix, causing sharp strength loss due to evapo-ration of bound and unbound water in the binding matrix. Others reported anenhanced heat resistance due to the formation of stronger clusters of C-S-H andrestricted size of calcium hydroxide crystals as a result of pozzolanic behavior ofthe mineral admixtures.

Recently, with the introduction of nanomaterials to the concrete industry, new op-portunities have arisen to study the effects of additives on microstructural changesand chemical composition of the binding matrix. This is due to remarkable effectof their nano sized particles on the binding matrix. Incorporation of nanomaterialsin the heat exposed binding matrix may clarify the mechanisms by which concreteis affected by high temperatures. It is also well established that the incorporationof nanomaterials can refine the binding matrix by chemical effects such as poz-zolanic reactivity, and that the physical filling and nucleation effects enhance themechanical properties and durability of concrete.

So far , some aspects of incorporation of nanomaterials in cementitous compositeshave been studied but there are still areas that need to be covered before massproduction of such concretes. Since nanomaterials considerably influence the for-mation of hydrated products, moisture content and permeability of the matrix, aninvestigation on the behavior of the binding matrix with nanomaterials after ex-posure to elevated temperature is indispensable. Moreover, the interlocking effectof nanomaterials in failure planes caused by heat exposure as well as modificationin hydration products may enhance the heat resistance of concrete. This studyintended to investigate the physical filling and nucleation effects, as well as thechemical effect of pozzolanic reactivity and shape of nanomaterials on the heatresistant behavior of HPC mortars and to identify the influencing factors on thebehavior of HPC binding matrix at elevated temperatures.

1.3 Objectives

The main aim of this research was to study the effect of adding nanomaterials inhigh performance concrete mortars when exposed to elevated temperatures.

This was realized through the following three objectives;

• To investigate the effects of nanomaterials on the microstructure and chem-ical composition of the binding matrix at ambient room temperature andafter exposure to elevated temperatures.

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• To investigate the effects of nanomaterials on the mechanical properties of thebinding matrix at ambient room temperature and after exposure to elevatedtemperatures.

• To identify the influencing factors on the behavior of the binding matrix inhigh performance concrete at elevated temperatures.

1.4 Research Questions

This study focused on the chemical and physical characteristics of nanomaterialsin order to answer the following questions;

1. How can different characteristics of nanomaterials namely interlocking, nu-cleation, and pozzolanic activity affect the heat resistant behavior of thebinding matrix?

2. Which is the most dominant factor influencing the behavior of mortars afterbeing exposed to elevated temperatures: permeability, formation of hydra-tion products or moisture content?

1.5 Significance of the Study

This study intended to investigate modification of the binding matrix by incorpo-ration of nanomaterials at elevated temperatures. The selection of nanomaterialsfollowed two criteria; their potential to enhance heat resistance of the binding ma-trix, and secondly to investigate the most dominant factor influencing the behav-ior of binding matrix after being exposed to elevated temperatures when additiveswere present in the mix. Knowledge derived from the findings of this study couldelaborate the behavior of the binding matrix at elevated temperatures which mayincrease the knowhow of the industry to avoid structural disasters when concretestructures are subjected to high temperatures and ensure the built infrastructuresare able to endure accidental exposures to fires. Also, it may introduce a processby which the binding matrix of concrete can be modified in order to be used inenvironments where temperature may be elevated to 400 ◦C to 600 ◦C. The in-troduction of a heat resistant Portland cement concrete may also change the heatrelated building codes in terms of concrete cover thickness and etc. Furthermore,the results of this study may solve the arising problems related to the incorpora-tion of silica fume, as the mostly used mineral admixtures in the HPC, at elevatedtemperatures.

1.6 Scope of Research

The overarching purpose of this study is to introduce mechanisms by which nano-materials modify the heat resistant behavior of the binding matrix in high perfor-mance Portland cement concrete at elevated temperatures. To do so, this studyfocused on the microstructural changes and chemical composition of the binding

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matrix of high performance mortars with the presence of four different types ofnanomaterial at different temperatures of 28 ◦C, 100 ◦C, 200 ◦C, 300 ◦C, 400 ◦C,600 ◦C, 800 ◦C and 1000 ◦C. Aggregates with size bigger than 4.75 mm were ex-cluded from this study in order to minimize the effect of aggregates on behavior ofthe binding matrix due to their volume concentration and the amount of interfa-cial area per unit volume. Nano silica, nano titania, nano alumina, and halloysitenano clay were chosen as additives due to their characteristics either in shape orchemical compositions and were added in fractions of 1, 2 and 3%. The targettemperature at which the heat resistance needs to be enhanced is 600 ◦C whereusing refractory castables are not economical. The effects of the modification ofthe matrix at 28 days on behavior of the mortars at elevated temperatures wereconsidered and early hydration was not studied.

In this study, compressive strength, XRD, DSC, SEM, gas permeability, and massloss were major tests conducted to trace properties of mortars both at room tem-perature and at elevated temperatures. All results were obtained in residual stateafter exposure to elevated temperatures with 1 hour steady state and the effect ofcyclic heating was not investigated in this study. Also, spalling was not targetedin this study since it mostly occurs in large surfaces of the structural members andthe heat exposed damages in mortars can be traced by cracks and sharp strengthloss.

1.7 Overview of the Thesis

The following four chapters shall describe the research work done in this thesis asfollows;

Chapter 2 initially discusses the microstructural differences between normal andhigh performance concrete. Then the effects of elevated temperatures on the chem-ical composition, microstructure and residual mechanical properties of concrete arementioned, and how high performance concrete varies in behavior after being ex-posed to elevated temperatures is further discussed. This chapter also reviews theinfluencing factors on the behavior of high performance concrete when exposedto high temperatures. Moreover, some efforts to enhance the heat resistance ofcementitous composites are reviewed. In the remaining sections of this chapterthe mechanical properties, durability and microstructural changes of paste, mor-tar and concrete containing targeted nanomaterials are reviewed.

In chapter 3, the methodology including materials, sample preparation and tem-perature exposure are described and the different tests which were conducted arementioned. These tests were implemented to study the mechanical properties ofmortars which included compression, brittleness index, energy absorption, and rel-ative elastic modulus as well as chemical composition and microstructural changesnamely XRD, SEM, DSC , gas permeability, and mass loss of samples after beingexposed to elevated temperatures. Figures and images are used to illustrate the

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tests clearly.

Chapter 4 discusses test results for halloysite nano clay, nano silica, nano tita-nia, and nano alumina, respectively. This chapter tends to compare and introducethe most advantageously effective amount of nanomaterials to be used in mortarswith the behavior at elevated temperatures. In this chapter the author aimedto discuss the most important effect of nanomaterials on the behavior of bindingmatrix after being exposed to elevated temperatures.

Finally, Chapter 5 provides a summary and conclusion of the study and suggestssome recommendation for further research in this area of knowledge.

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