CONGLASSCRETE I - …webarchive.nationalarchives.gov.uk/20100503135839/http:/wrap.org...5.4 Test Methods 12 5.5 Sub-Project Descriptions 13 5.6 Results and Discussion 21 5.6.1 ASR

CONGLASSCRETE I

Project code: GLA2-006

Date of commencement of research: 01/04/2002 Completion date: 31/03/04 Final Report Written by: Dr EA Byars, HY Zhu and Dr B Morales The University of Sheffield Published by: The Waste & Resources Action Programme The Old Academy, 21 Horse Fair, Banbury, Oxon OX16 0AH Tel: 01295 819900 Fax: 01295 819911 www.wrap.org.uk WRAP Business Helpline: Freephone: 0808 100 2040 March 2004 ISBN: 1-84405-115-3

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Final Report, March 2004 i

Content

EXECUTIVE SUMMARY iii LIST OF ABBREVIATIONS iv CHAPTER 1. INTRODUCTION 1 1.1 Overview 1 1.2 Aims and Objectives 2 1.3 Structure of The Report

CHAPTER 2. LITERATURE REVIEW 3 2.1 Background 3 2.2 Historical Use of Glass in Concrete 3 2.3 Alkali Silica Reaction (ASR) 4 2.3.1 Mechanisms of ASR 4 2.3.2 Methods of ASR Mitigation 4 2.3.3 ASR Test Methods 4 CHAPTER 3. PROJECT STRUCTURE 7 3.1 Project Overview 7 3.2 Industrial Collaborations and Steering Committee 8 CHAPTER 4. DISSEMINATION EXERCISES 9

CHAPTER 5. INDUSTRIAL SUB-PROJECTS 11 5.1 Introduction 11 5.2 Materials 11 5.3 Mix Proportions 12 5.4 Test Methods 12 5.5 Sub-Project Descriptions 13 5.6 Results and Discussion 21 5.6.1 ASR 21 5.6.2 Product Compliance Testing 21 5.6.3 Scanning Electron Microscopy (SEM) 22 5.4 X-Ray Diffraction Analysis (XRD) 24

Final Report, March 2004 ii

CHAPTER 6. LABORATORY ASR STUDY 26 6.1 Materials 26 6.2 Mix Proportions 27 6.3 Test Methods 27 6.4 Results and Discussion 27 6.4.1 ASR 27 6.4.2 Scanning Electron Microscope 33 6.5 Architecture Concrete Finishes 37 CHAPTER 7. SPECIFICATIONS FOR WASTE GLASS AS A POZZOLAN

AND AN AGGREGATE IN CONCRETE 44 7.1 Introduction 44 7.2 Specification for Use of Glass as a Pozzolan in Concrete, Mortar or Grout 44 7.3 Specification for Use of Glass as an Aggregate in Concrete 46 CHAPTER 8. NATIONAL CULLET USAGE DATA 49 CHAPTER 9. CONCLUSIONS 51 REFERENCES 52 APPENDICES Appendix A. Newsletters A1 Appendix B. List of Subscribing Companies B1-B7 Appendix C. Mix Proportions and Detailed Results of Sub-Projects C1-C31 Appendix D. Listing of Long Term ASR Test Specimens D1-D3 Appendix E. ConGlassCrete Bibliography E1-E163

Final Report, March 2004 iii

Executive Summary This document reports the work conducted within the WRAP-funded ConGlassCrete I Project (contract GLA2-006). This project has conducted what is believed to be the widest-ever study of the performance of crushed and ground glass in real concrete products as a replacement for cement and/or aggregate. A total of 19 products, (98 mixes) were manufactured in precast concrete factories around the UK and tested for compliance with type-testing to British Standards, glass reactivity in alkali by the alkali-silica reaction (ASR) test and advanced chemical analysis including scanning electron microscopy by major concrete companies, Glass Technology Services and Sheffield University. Full results are given within this report, but the major findings are that i) all products made with glass as aggregate were found to have equivalent type-test results as products with no glass and ii) after one year, dimensional tests indicate that detrimental reaction between the cement and glass only occurs when high-alkali Portland cement is used. Whilst the findings above give considerable confidence to concrete producers, it is essential that the 98 product mixes, which remain in a conditioned environment at Sheffield, are tested for a longer period. Without this it is unlikely that glass aggregates could receive a 3rd-Party certification for use in concrete. The project also conducted a very wide parametric laboratory study into the effects of glass aggregates in concrete. This study found that i) glass can react in concrete and the reactivity increases with cement alkali content and particle size above 1mm, and ii) that glass of particle size less than 1mm may reduce ASR effects. Colour effects were unclear and it is felt that differences may be more related to crushing technique, which causes microcracks where ASR gel grows, than slight differences in glass chemistry. ASR suppressants were also investigated and this aspect of the project was extremely successful. Both dimensional measurements and scanning electron microscopy confirmed the following i) the most important parameter affecting glass aggregate reactivity in concrete is cement alkali level, ii) irrespective of glass type or particle size, the ASR reactivity can virtually be reduced to zero (at least in the short term) by using pulverised-fuel ash (PFA), ground-granulated blast-furnace slag (GGBS) or metakaolin (MK) at normal replacement levels for Portland cement. Specifications for glass as a pozzolan and an aggregate in concrete have been proposed. These are in a form that is similar to British Standards and could easily be adopted by industry. For glass aggregate, longer term testing of the Sheffield glass-in-concrete library is required to take this further than a tentative specification. The results of this study have already been widely disseminated by 6 Newsletters, 5 Steering Group Meetings, 2 National Seminars, 2 journal and 2 conference papers, press articles, a front page spread on “Concrete” magazine and a 100-page web-site, with up to 1000 hits/day.

Final Report, March 2004 iv

List of Abbreviations used in the report Glass Powder AP: amber glass pozzolan FP: flint glass pozzolan GP: green glass pozzolan Glass Aggregate AGA: amber glass aggregate BGA: blue glass aggregate FGA: flint glass aggregate GGA: green glass aggregate FGS: flint glass sand GGS: green glass sand BBUW: unwashed post-consumer bottle banks collection cullet BBW: washed post-consumer bottle banks collection cullet P&CUW: unwashed post-consumer pub & club collection cullet P&CW: washed post-consumer pub & club collection cullet Cementitious Materials OPC: ordinary Portland cement HAPC: high alkali Portland cement WPC: white Portland cement PFA: pulverized-fuel ash CPFA: run-of-station PFA SPFA: super classified PFA GGBS: ground granulated blast furnace slag MK: metakaolin MS: micro silica Others LS: lime stone RCA: recycled concrete aggregate

Final Report, March 2004 1

Chapter 1. Introduction

1.1 Overview This report details the work carried out at the Centre for Cement and Concrete, University of Sheffield, from April 2002 to March 2004 to increase the use of mixed colour cullet re-processing and reuse by developing added-value end use markets in the concrete products sector. It fulfils all milestones and deliverables of the Project. The quantitative tasks that have been completed in the Project are as follows:

• 20 collaborative industrial sub-projects (12 more than originally planned);

• A wide laboratory studies on glass ASR reactivates (in addition to original plan);

• 30 architectural glass aggregate concrete finishes (in addition to original plan);

• A website with over 100 pages of publicly-available information;

• An online glass literature database (4,000 references) publicly available;

• 6 Newsletters;

• 500 relevant industrial sectors subscribed to the Project;

• Two conference papers published (Feb/Sept 2003) and one submitted in January 2004;

• An interim report published by WRAP in November 2003;

• Journal papers published in January 2004 and submitted in March 2004.

1.2 Aims and Objectives The ConGlassCrete I project aimed to effect a significant step-change in the amount of waste container glass used in concrete construction by the development of appropriate added-value end uses in concrete products and to facilitate the increase of this market in future years. In order to achieve these aims, a series of objectives were identified as follows:

• To determine the most significant barriers and incentives to increasing glass recycling at national and regional levels;

• To develop partnerships between glass legislative bodies, collectors, reprocessors, the cementitious materials industry and the precast concrete products and ready-mix concrete industries to effect changes in attitude, working methodologies and raw materials usage;

• To research and develop markets in the concrete products industry for the use of reprocessed mixed cullet and to facilitate concrete products companies becoming accredited re-processors for Packaging Recovery Notes (PRNs);

• To encourage profit-share between the collection, processing and end-use business sectors;

• To utilise current knowledge to design comprehensive durability and engineering property research projects on specific concrete products and thereby facilitate the use of ground cullet as aggregate and cement by the precast and ready-mix concrete industries;

• To write product-specific technical specifications based on the project research and to disseminate these widely;

• To propose amendments to standards for aggregates and cementitious materials to accommodate glass as a fit-for-purpose material in a range of concrete products;

• To link with concrete products and glass Trade Associations and their members to effect maximum dissemination of the project outcomes;

• To further disseminate the results of this study to the industry at large by means of 2 National Seminars, published papers and a dedicated web-site;

• To compile a well-targeted, national associate partnership to this project, who will be kept informed of the general progress of the project via an e-mailed 3-monthly newsletter and invited to the Dissemination Seminars with a view to stimulating additional supply and demand for mixed cullet in concrete.


1.3 Structure of the Report The report is organised as follows:

Chapter 2: presents a review of available literature related to the use of waste glass in concrete and the alkali silica reaction;

Chapter 3: describes the project structure and industrial collaboration;

Chapter 4: describes the dissemination of the Project information;

Chapter 5: gives the detailed results and discussion of the industrial sub-projects;

Chapter 6: gives detailed results and discussion of laboratory study;

Chapter 7: presents a specification for use of waste glass in precast concrete products as a pozzolan and an

aggregate;

Chapter 8: presents data on national cullet usage;

Chapter 9: presents the main conclusions of this Project.


Chapter 2. Literature Review

2.1 Background Post-consumer and other waste glass types are a major component of the solid waste stream in many countries and most is currently landfilled [1]. Several European Directives have tackled this problem by setting recovery and recycling targets for specific waste glass streams [2-4]. The EU Landfill Directive 1999/31/EC [5] and the UK Landfill Tax Regulations [6] have emerged to divert such waste into recovery and recycling programmes and, specifically for post-consumer glass, the Packaging Waste Regulations [2] have provided legislative pressure to increase recovery and recycling. Recovered waste glass can be infinitely remelted without degradation of its physical properties and, theoretically at least, the glass manufacturing industry could use 100% recycled glass as a primary feedstock. However due to tolerances on contamination there is a practical limit and it is estimated [7] that approximately 650,000 tonnes/year of waste container glass cannot be recycled into new glass manufacture. There are also arisings of over 1m tonnes/year from other waste glass streams (e.g. plate glass, windscreens and lighting) that could be recovered and re-used. Whilst some markets for recycled waste glass already exist in construction (170,000 tonnes as aggregate in asphalt, pipe bedding, backfill, loose fill, decorative aggregate and golf bunkers), there is a huge potential for this to increase in the concrete construction sector. Published research work in the UK, USA and other countries since 1997 [1, 8-13] has shown that finely-ground waste glass will react in a pozzolanic manner in cementitious systems and contribute to the strength development of concrete. This means that raw post-consumer glass could be processed and used to replace a percentage of the Portland cement in concrete mixes. Considering the size of the cement industry (over 10 million tonnes/annum in the UK) this would appear to be a potential high volume, economic and environmentally friendly solution to part of the waste glass problem. Alternatively, waste glass could be used as a concrete aggregate; either as a direct replacement for normal concrete aggregates (low value) or as an exposed, decorative aggregate in architectural concrete products (high value). Expansive alkali-silica reactions (ASR) can occur between glass particles and cement paste [14-18], particularly in moist conditions and with high alkali cements [16]. Of course, this reaction is not confined to glass aggregates but can occur whenever aggregates contain reactive silica. However it is now fairly-well accepted that by controlling the reactive silica, cement alkali level and moisture, the reaction can be reduced or totally mitigated [19, 20]. Thus, the use of pozzolanic mineral admixtures that react with and reduce the alkalinity of cementitious systems, low alkali cements and indoor (dry) concrete environments are potential ASR mitigators when glass aggregates are used. Researchers in the US [11, 14] have used alkali-resistant glass and glass modified by the addition of minor constituents at the melt stage. These latter two methods of avoiding ASR may have potential benefit in concrete applications if post-consumer glass were to be melted and re-colored specifically for the highly lucrative decorative concrete aggregate market.

2.2 Historical Use of Waste Glass in Concrete There has been a general perception in the concrete construction industry that glass aggregates should be precluded from concrete because of their potential for alkali silica reaction (ASR), even although early research [20-22] did not draw definite conclusions. Recent publications [23-25], whilst not specifically supporting the use of glass in concrete, have led to a great understanding of ASR parameters and methods by which it can be suppressed and major recent research in the USA and UK [8-12, 14-16, 18] has made it possible for recycled glass to be viewed as a potentially “fit-for-purpose” concrete construction material. Early researches in 1960s, 1970s and 1980s [22-24] on the study of ASR of glass aggregate were conducted without definite conclusions.

In parallel to these scientific advances, changes in environmental legislation [5-6, 25] are positively encouraging the use of secondary aggregates in concrete and waste glass is becoming available in larger quantities as container, end-of-life vehicle and waste electrical goods [2-4] legislation take effect.


2.3 Alkali Silica Reaction (ASR) 2.3.1 Mechanisms of ASR

Alkali-silica reaction (ASR) is the reaction that occurs between hydroxyl ions in concrete pore water and certain forms of silica which may be present in some aggregates. The product of this reaction is a gel which imbibes water and swells. If sufficient reaction and swelling takes place, the pressures induced cause micro-cracking, expansion and ultimately deterioration of the surrounding concrete [19]. The parameters affecting the ASR reaction are complex and one theory [28] explains ASR as follows:

1) OH- attacks the reactive silica and provokes dissolution; 2) dissolved silica(te) reacts with alkali (Na+ or K+) to form alkali-silica gels; 3a) concrete expands due to the osmotic pressure generated by alkali silica(te) gels which are confined within a semi permeable membrane of cement paste; 3b) the expansion is a consequence of the formation and subsequent widening of cracks due to mechanical pressure exerted by the reaction products; 3c) the expansion of the concrete depends on the type of reaction products, i.e. swelling alkali-silica gel or non-swelling lime-alkali-silica gel.

The chemical reactions are generally agreed to be a two step phenomenon [29, 30] as shown below: i) Attack of the silanol groups of the reactive silica by hydroxyl ions

- Si – OH + Na+ + OH- → - Si – Na+ (gel) + H2O (2.1)

ii) Attack of the siloxan bridges in the silica by hydroxyl ions - Si – O – Si + 2NaOH → Si – O – Na+ (gel) + Na+ - O – Si – (gel) + H2O (2.2)

2.3.2 Ways to Mitigate ASR

The most common ways to mitigate ASR are [19, 20, 24, 31-33]: • Using non-reactive aggregates • Limiting the alkali content of cement and concrete • Using cement replacement materials and chemical admixtures such as lithium compound • Isolating concrete from moisture

Among these, the most common measure is the use of cement replacement materials (ASR suppressants) including micro-silica (MS), pulverized-fuel ash (PFA), ground granulated blast-furnace slag (GGBS) and metakaolin (MK) as summarised in Table 2.1.

Table 2.1. Suggested minimum replacement levels of suppressants

SUPPRESSANTS REPLACEMENT LEVEL (% of cement) REFERENCE

PFA 20-30 [19, 34-37]

GGBS 25-50 [19, 36]

MS 10-20 [19, 38, 39]

MK 10-20 [9-11, 39, 40]

2.4.3 ASR Test Methods

Various test methods are available to identify alkali-reactive aggregates and their potential for deleterious expansion in concrete. These laboratory tests can often be difficult, complex, confusing, time-consuming and even inconclusive [33, 41]. Nevertheless, they provide the only way to assess and evaluate the potential reactivity of aggregates prior to their use in concrete construction. The main methods include ASTM C227 [42], C289 [43], C295 [44], C441 [45], C856 [46], C1260 [47], C1293 [48] and BS 812-133 [49].


These are described in more details in Tables 2.4(a) and 2.4(b). To date, no single test has been internationally accepted and for high reliability a combination of petrographic studies, field performance and a concrete prism test is recommended.

Table 2.4(a). Standard test methods for assessing alkali-silica reactivity [32]

TEST METHOD COMMENTS

ASTM C 227: Standard Test Method for Potential Alkali

Reactivity of Cement-Aggregate Combinations

(Mortar-Bar Method)

• Mortar bar test (aggregate/cement = 2.25), intended to study cement-aggregate combinations.

• Specimens stored in high-humidity containers at 38°C. • Several reported problems, including excessive leaching of alkalis from

specimens.

ASTM C 289: Standard Test Method for Potential Alkali-Silica Reactivity of Aggregates (Chemical Method)

• Aggregate test in which crushed aggregate is immersed in 1M NaOH solution for 24 hours — solution is then analyzed for amount of dissolved silica and alkalinity.

• Poor reliability. • Problems with test include:

o Other phases present in aggregate may affect dissolution of silica (Bérubé and Fournier, 1992).

o Test is overly severe, causing aggregates with good field performance to fail the test.

o Some reactive phases may be lost during pre-test processing.

ASTM C 295: Standard Guide for Petrographic Examination of Aggregates for Concrete

• Useful evaluation to identify many (but not all) potentially reactive components in aggregates.

• Reliability of examination depends on experience and skill of individual petrographer.

• Results should not be used exclusively to accept or reject aggregate source - best used in conjunction with other laboratory tests (e.g., ASTM C 1260 and/or ASTM C 1293.

ASTM C 856: Practice for Petrographic Analysis of Hardened Concrete

• Useful for analyzing concrete (from laboratory or field) and for identifying presence of reactive aggregates or reaction products.

• Reliability of examination depends on experience and skill of individual petrographer.

• Essential for relating aggregate reactivity to field performance.

ASTM C441: Standard Test Method for Effectiveness of Mineral Admixtures or Ground Blast-Furnace Slag in Preventing Excessive Expansion of Concrete Due to the Alkali-Silica Reaction

• Mortar bar test, intended to assess effectiveness of cementitious materials in reducing ASR expansion.

• Test uses high-alkali cement and Pyrex glass.

• Test not very reliable because of the use of Pyrex glass, which is sensitive to test conditions and contains alkalis that may be released during the test. Test does not correlate well with data from concrete mixtures containing natural aggregates.


Table 2.4(b).Standard test methods for assessing alkali-silica reactivity – continued [32]

TEST METHOD COMMENTS

ASTM C 1260: Standard Test Method for Potential Alkali Reactivity of Aggregates (Mortar-Bar Method) •Recommended Test

• Mortar bar test, originally designed to assess aggregate reactivity. • Bars are soaked in 1N NaOH solution for 14 days. • Accelerated test suitable as screening test, but because of severity

of test, it should not be used, by itself, to reject a given aggregate. If aggregate is tested using both ASTM C 1260 and ASTM C 1293, the results of ASTM C 1293 should govern.

• Test has shown promise in testing suppressants

ASTM C 1293: Standard Test Method for Concrete Aggregates by Determination of Length Change of Concrete Due to Alkali-Silica Reaction •Recommended Test

• Concrete prism test, generally regarded as best indicator of field performance, is conducted at high humidity (close to 100%) at 38 °C.

• Uses high-alkali cement (raised to 1.25% Na20eq), with a cement content of 420 kg/m3.

• Originally intended as aggregate test (using non-reactive fine aggregate to test reactivity of coarse aggregate, and vice-versa); test requires one year for completion.

• Also can be used to test effectiveness of suppressants and lithium compounds, but test is then typically run for two years.

• Widely-accepted test method, but long duration of test is major drawback.

BS 812-123: Testing Aggregate – Method for Determination of alkali-silica reactivity – Concrete Prism Method •Recommended Test

• Concrete prism test, generally regarded as best indicator of field performance, is conducted at high humidity (close to 100%) at 38 °C.

• Uses high-alkali cement (>1.0% Na20eq), with a cement content of 690 kg/m3.

• Originally intended as aggregate test (using non-reactive fine aggregate to test reactivity of coarse aggregate, and vice-versa); test requires one year for completion.

• Widely-accepted test method, but long duration of test is major drawback.


Chapter 3. Project Structure

3.1 Project Overview An overview of the ConGlassCrete I Project and the interlinked ConGlassCrete II Project is shown in Figure 3.1.

ConGlassCrete I ConGlassCrete II Overlap of ConGlassCrete I & II

Figure 3.1. Overview of ConGlassCrete I and II Projects

CONGLASSCRETE PROJECTS

Post-consumer, plate, automotive, lighting, fibres

Measurement of Contamination, (selectively)

Assessment of Waste Glass Streams

Pozzolanic Reactivity

Certification of glass as pozzolan for concrete to

BS EN450

Effect of: Source, Colour, Contamination

Certification of glass for concrete products

Paving slabs, cast stone, blocks, pavers, flags,

kerbs, roof tiles

Test methods: ASTM C1260 & C227, BS 812-123, modified

Effect of: Colour, Grading, Suppressants

Clean sources

Contaminated sources

Bottle bank, pub and club collection

Alkali-Silica Reaction (Laboratory and industrial study)

20 Full-scale industrial projects


3.2 Industrial Collaborations and Steering Committee The ConGlassCrete I Project had 26 collaborating partners, Table 3.1, all of whom were represented on the Project Steering Committee. Each partner positively contributed to the Project by supplying materials, grinding facilities, full-scale factory trials and senior management time as appropriate.

Table 3.1. ConGlassCrete I Project Steering Committee Members

CONGLASSCRETE PROJECT PARTNERS

Industrial and in-kind Funding Organisations Funding Bodies Academic Glass

Industry Trade

Association Environmental

Body Cement & Concrete

WRAP, University

of Sheffield

CCC, BRE, Chris

Coggins, Columbia University

GTS, Northern Cullet,

Valpak Ltd, Mac-Glass

BCA, UKQAA,

British Glass

Wales

Environmental Trust,

Business Environmental

Partnership

Aggregate Industries, Appleby Group,

BRE Certification, Conways Concrete,

CRH Group (Forticrete), H&H,

Marshalls Mono, Stowell Concrete, Tarmac Group, Trent Concrete


Chapter 4. Dissemination Exercises

The ConGlassCrete I Project continuously disseminated its findings by:

• 5 well-attended Steering Group Meetings over 2 years

• Publication of 6 newsletters (Appendix A)

• 3 Conference papers [18, 50, 51]

• 2 Journal papers [16, 52]

• Regular web-site updates (www.wrap.org.uk/conglasscrete)

• A series of press releases and press articles in the waste management and construction press (www.wrap.org.uk/conglasscrete/cgc_press.asp)

In addition, the ConGlassCrete I Project has around 500 UK Subscribers, Table 4.1, distributed as shown in Figure 4.1. Appendix B lists detailed subscribing companies.

Table 4.1. Range of ConGlassCrete Projects Subscribers

SCOPE BUSINESS NO OF COMPANIES

Glass Collection 43

Glass Processing 33

Portland Cement 21

Cementitious Materials 25

Concrete Aggregates 43

Ready Mixed Concrete 28

Precast Concrete 51

Local Authority 79

Education 34

Research and Development 37

Consultant Engineer 18

Waste Legislation 21

Environmental 16

Others 51

TOTAL 500


(a) ConGlassCrete Subscribers

(b) ConGlassCrete Partners

Figure 4.1. Geographical distribution of the ConGlassCrete Project Subscribers and Partners


Chapter 5. Industrial Sub-Projects

5.1 Overview 20 Sub-projects have been carried out using glass as pozzolan and aggregate in precast and ready mixed concrete products, Table 5.1.

Table 5.1. The industrial sub-projects

SUB-PROJ. NO. COMPANY DESCRIPTION NO. OF

TRIALS

1 H&H Use of Glass Aggregate and Pozzolan in Pre-cast Concrete Paving Slabs 8

2 Use of Glass Pozzolan and 1-3mm Glass Sand in Semi-dry Cast Concrete Stone 3

3 Use of Glass Pozzolan in Semi-Dry Cast Concrete Grey Blocks 3

4

CRH (Forticrete)

Use of Glass Aggregate and Pozzolan in Medici Architectural Masonry 9+6

5 Use of Glass Pozzolan in Fielding and Platt Process Slabs 6

6 Use of Glass Pozzolan and Aggregate in Fielding and Platt Process Slabs 6

7

Aggregate Industries UK

Use of Glass Pozzolan in Semi-Dry Cast Block Pavers 6

8 Glass as Exposed Aggregate in Concrete flags 5+5

9 Use of Glass Pozzolan in Semi-Dry Cast Block Paving 2+2

10 Use of Glass Pozzolan in Wet-Casting Concrete Paving 3

11

Marshalls Mono

Use of Glass Pozzolan in Hydraulic Wet-Press Concrete Paving 3

12 Use of Glass Pozzolan in Low-Grade Ready-mix Concrete 7

13 Tarmac Group

Use of Glass Pozzolan and Sand in Low-Grade Ready-mix Concrete 6

14 Assessment of Crushed Glass Product (Analysed by GTS) 2

15

Stowell Concrete Use of Glass Pozzolan and Aggregate in Semi-dry Concrete Blocks 5

16 Conways Use of Glass Pozzolan and Aggregate in Semi-dry Concrete Blocks 6

17 Aggregate Industries UK Use of Glass Pozzolan and Aggregate in Wet-Pressing Concrete Kerbs 3

18 Stowell Concrete Use of Glass Pozzolan and Aggregate in Semi-dry Cast Concrete Feet 6

19 Trent Concrete Decorative Exposed Glass Aggregate Concrete Products 8

20 CRH (Forticrete) Use of Glass Pozzolan and Sand in Cast Concrete Roof Tiles 7

TOTAL MIXES 117

5.2 Materials Most of the raw glass materials were supplied by Northern Cullet Ltd and prepared for use in concrete at the CCC. In addition, Valpak Ltd supplied raw post-consumer container glass from pub and club collection (P&C) directly to Stowell Concrete Ltd for full-scale trials. Conways Concrete has its own raw post-consumer container glass from bottle bank collection (BB). Some 7000kg of glass aggregate (0.2-12mm) and 1500kg of glass powder (<0.2mm) have been used in the project. Other concreting materials and facilities (cement, sand, aggregates, admixtures and full scale factory trials) were supplied by the cement and concrete industrial partners. A typical particle size distribution of glass pozzolan and grading of various glass aggregate used in the sub-projects are shown in Figures 5.1(a)-(d).


0

20

40

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0 20 40 60 80 100Particle Size (µm)

Perc

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(a)

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0 2 4 6 8 10 12Sieve Size (mm)

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)

BB CulletLab SandP&C CulletBS Low LimitsBS High Limits

(b)

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60

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2 4 6 8 10 12 14Sieve Size (mm)

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GGA6-12FGA6-12AGA6-12BGA6-12Norm.5-10BS Low limitsBS High Limits

(c)

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2 4 6 8 10 12 14

Sieve Size

Perc

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GGA3-6FGA3-6AGA3-6BGA3-6BS Low limitsBS High Limits

(d)

Figure 5.1. (a) particle size distribution of glass pozzolan; (b) grading of post-consumer cullet; (c) grading of 6-12mm glass aggregate and (d) grading of 3-6mm glass aggregate.

5.3 Mix Proportions Mix proportions of the precast concrete products and ready-mixed concrete with glass are given in Appendix C. It should be noted that the concrete companies’ control mix proportions are not included for reasons of confidentiality.

5.4 Test Methods Most of the sub-project specimens are still being monitored for ASR to BS 812:123 [49] at the CCC. Product specific compliance tests including tensile strength, abrasion, slip/skid resistance and freeze-thaw resistance were tested to BS 6073 [53, 54], BS 6717 [55], BS 7263 [56, 57], BS EN490 & 491 [58, 59] and BS EN1338 [60] as appropriate by the partner companies. In addition, 15 industrial sub-project samples have been examined by scanning electron microscopy (SEM) to explain the trends observed in the expansion tests, Table 5.2. Several industrial sub-project samples (two samples each selected sub-project) were tested with an x-ray diffraction (XRD) method to study the cement phase development when glass is used as pozzolan, Table 5.3.


5.5 Sub-Project Descriptions Sub-Project 1 – Wet Cast Concrete Slabs

6-12mm green, amber, flint glass aggregate and green glass pozzolan (80% passing 35µm) were used in wet-cast concrete slabs at H&H Fencing Precast Concrete Products laboratory in Fleetwood. Seven concrete mixes were cast

Table 5.2. Samples examined by SEM analysis

Sub-Projects No. Type Products Cement/Glass tested

1 wet cast Slab OPC, 15%GP, 100%6-12mm FGA

2 Semi-dry Cast stone WPC, 40%GP

3 Semi-dry Grey blocks OPC, 30%AP

4 Semi-dry Masonry units WPC, 20%GP, 100& 6-12mm BGA

5 Wet-pressed Slab OPC, 30%GP

6 Wet-pressed Slab OPC, 10%GP, 100% 6-12mm FGA

7 Semi-dry Paving blocks OPC, 30%GP

8 Wet cast Flags HAPC, 10%GP, 100% 6-12mm AGA

10 Wet cast Flags OPC, 20%GP

12 Wet cast Ready mix OPC, 50%GP

13 Wet cast Ready mix OPC, 25%GP, 50% 1-3mm green sand

15 Semi-dry Grey blocks OPC, 15%AP, 15% pub and club cullet

16 Semi-dry Grey blocks OPC, 100% bottle bank cullet

18 Semi-dry Non-BS OPC, 100% Flint glass sand

20 Semi-dry Roof tiles OPC, 17% Flint glass sand

Table 5.3. Samples examined by XRD analysis

Sub-proj. No. Type Products Cement/Glass tested

2 Semi-dry Cast stone WPC/GGBS40, WPC/GP40

4 Semi-dry Masonry units WPC, WPC/GP20

7 Semi-dry Paving blocks OPC/PFA25, OPC/GP25

10 Wet cast Flags OPC, OPC/GP20

12 Wet cast Ready mix OPC, OPC/GP50

16 Semi-dry Grey blocks OPC, OPC/GP20

20 Semi-dry Roof tiles OPC, OPC/GP20

including one control mix using OPC and normal aggregate. For each mix, 4 100mm3 cubes and 2 75 75 280 mm prisms were cast for strength ASR respectively. One mix was selected for SEM examination.


Sub-Project 2 – Semi-Dry Cast Stone

Green glass pozzolan (80% passing 35µm) was used in semi-dry cast concrete stone at Masoncrete Factory facilities, CRH Forticrete Group, in Matlock, Figure 5.2. Three concrete mixes were cast including one control mix using white PC/GGBS. For each mix, 4 100mm3 cubes, two 75 75 280 mm prisms some cast stones were cast for strength, water absorption and ASR tests respectively. One mix was selected for SEM examination and 2 for XRD analysis.

Figure 5.2. Samples of semi-dry cast concrete stone Sub-Project 3 – Semi-Dry Cast Grey Blocks 1

Raw amber glass pozzolan (80% passing 75µm) was used in semi-dry cast concrete grey blocks at CRH Group - Forticrete in Dewsbury. Three concrete mixes were cast including one control mix using OPC and normal aggregate, Figure 5.3. For each mix, 6 blocks and two 75 75 280 mm prisms were cast for strength and ASR tests respectively. One mix was selected for SEM examination.

Figure 5.3. Samples of semi-dry cast grey blocks Sub-Projects 4 – Semi-Dry Cast Architectural Masonry Units

6-12mm green, amber, flint, blue glass aggregate and green glass pozzolan (80% passing 35µm) were used in semi-dry cast concrete architectural masonry units at the CRH Group Forticrete, in Shotton Colliery, Figure 5.4.


16 concrete mixes were cast including one control mix using white PC and normal aggregate. For each mix, two 100 190 390 mm concrete blocks, two 75 75 280 mm prisms were cast for strength and ASR tests respectively. One mix was selected for SEM examination and 2 for XRD analysis.

Figure 5.4. Samples of semi-dry cast architectural masonry units Sub-Projects 5 & 6 Wet Pressed Slabs

6-12mm green, flint glass aggregate and green glass pozzolan (80% passing 35µm) were used in wet pressed concrete slabs at the laboratory of Aggregate Industries UK – Charcon Division, in Hulland Ward, Figure 5.5. 12 concrete mixes were cast including one control mix using OPC/PFA and normal aggregate. For each mix, eight 100 mm concrete cubes and two 75 75 280 mm prisms were cast for strength, abrasion and ASR tests respectively. One mix was selected for SEM examination.

Figure 5.5. Samples of wet pressed slabs

Sub-Project 7 – Semi-Dry Cast Paving Blocks 1

Green glass pozzolan (80% passing 35µm) was used in semi-dry cast concrete paving blocks at Aggregate Industries UK – Charcon Division, in Middleton-by-Wirksworth, Figure 5.6. Five concrete mixes were cast including one control mix using OPC and normal aggregate. For each mix, a number of blocks were cast for strength and type tests, and two 75 75 280 mm prisms were cast at the CCC laboratory later for ASR testing. One mix was selected for SEM examination and two for XRD analysis.


Figure 5.6. Samples of semi-dry cast paving blocks Sub-Project 8 – Wet Cast Exposed Aggregate Flags

6-12mm green, amber, flint glass aggregate and green glass pozzolan (80% passing 35µm) were used in wet cast exposed aggregate concrete flags at the Marshalls Mono laboratory, in Halifax, Figure 5.7. 10 concrete mixes were cast including 2 control mixes using high alkali and low alkali PC and normal aggregate. For each mix, four flags, eight 100mm cubes and two 75 75 280 mm prisms were cast for strength and ASR tests respectively. One mix was selected for SEM examination.

Figure 5.7. Samples of exposed glass aggregate flags

Sub-Project 9 – Semi-Dry Cast Paving Blocks 2

Amber glass pozzolan (80% passing 35µm) was used in semi-dry cast concrete paving blocks at the full-scale facilities of Marshalls Mono, in Ramsbottom, Figure 5.8. Four concrete mixes were cast including two control mixes using OPC and normal aggregate. For each mix, a number of blocks were cast for strength and type tests. One mix was selected for SEM examination.


Figure 5.8. Samples of semi-dry cast paving blocks Sub-Project 10 – Wet Cast Concrete Flags

Green glass pozzolan (80% passing 35µm) was used in wet cast concrete flags at the Marshalls Mono laboratory, in Halifax, Figure 5.9. Three concrete mixes were cast including one control mix using OPC and normal aggregate. For each mix, four flags, eight 100mm3 cubes and two 75 75 280 mm prisms were cast for strength and ASR tests respectively. One mix was selected for SEM examination and two for XRD analysis.

Figure 5.9. Samples of wet cast flags Sub-Project 11 – Wet Pressed Paving Flags

Green glass pozzolan (80% passing 35µm) was used in hydraulic wet pressed concrete paving flags made using full-scale facilities of Marshalls Mono, Halifax, Figure 5.10. Three concrete mixes were cast including one control mix using OPC and normal aggregate. For each mix, a number of flags were cast for strength and type tests. One mix was selected for SEM examination.

Figure 5.10. Samples of wet-pressed flags


Sub-Projects 12 & 13 – Ready Mixed Concrete

1-3mm green glass sand and green glass pozzolan (80% passing 35µm) were used in ready-mixed concrete at the laboratory of Tarmac Group, in Macclesfield, Figure 5.11. Twelve concrete mixes were cast including one control mix using OPC and normal aggregate. For each mix, thirteen 100mm3 cubes and two 75 75 280 mm prisms were cast for strength and ASR tests respectively. One mix was selected for SEM examination and two for XRD analysis.

Figure 5.11. Samples of ready mixed concrete Sub-Project 14 – Assess of Crushed Glass Product

Post-consumer glass directly from pub and club collection (P&C) was supplied by Valpak and processed as a fit-for-use aggregate for grey blocks production at Stowell Concrete Ltd, Figure 5.12. Samples were sent to GTS for as assessment of the contamination levels.

Figure 5.12. Samples of crushed P&C cullet Sub-Project 15 – Semi-Dry Cast Grey Blocks 2

Crushed pub & club (P&C) cullet, crushed recycled concrete aggregate (RCA) and amber glass pozzolan (80% passing 75µm) were used in semi-dry cast concrete grey blocks at Stowell Concrete Ltd in Yatton, Bristol, Figure 5.13. Five concrete mixes were cast including one control mix using OPC/PFA and normal aggregate. For each mix, a number of grey blocks and two 75 75 280mm prisms were cast for strength and ASR tests respectively. One mix was selected for SEM examination.


Figure 5.13. Samples of semi dry cast grey blocks 2 Sub-Project 16 - Semi-Dry Cast Grey Blocks 2

Crushed bottle bank (BB) cullet, 1-3mm green glass sand, 1.18mm to dust flint glass sand, amber/green glass pozzolan (80% passing 35 µm) were used to make semi-dry cast concrete grey blocks at Conway Concrete Ltd in Newport, Figure 5.14. Six concrete mixes were cast including one control mix using OPC and normal aggregate. For each mix, a number of grey blocks and two 75 75 280 mm prisms were cast for strength and ASR tests respectively. One mix was selected for SEM examination and two for XRD.

Figure 5.14. Samples of raw BB cullet and semi dry cast grey blocks 3 Sub-Project 17 – Wet Pressed Concrete Kerbs

3-6mm blue glass aggregate and green pozzolan (80% passing 35µm) were used to make wet pressed concrete kerbs, Figure 5.15, at the full-scale facilities of Aggregate Industries UK – Charcon Division, in Exeter. Three concrete mixes were cast including one control mix using OPC and normal aggregate. For each mix, a number of kerbs were cast for strength and type tests. One mix was selected for SEM examination.

Figure 5.15. Samples of wet-pressed concrete kerbs


Sub-Project 18 – Semi-Dry Cast Non-BS Product

3-6mm green glass aggregate and amber pozzolan (80% passing 75µm) were used in semi-dry cast non-BS concrete products at Stowell Concrete Ltd in Yatton, Bristol, Figure 5.16. Six concrete mixes were cast including one control mix using OPC and normal aggregate. For each mix, a concrete foot, two 100mm3 cubes and two 75 75 280mm prisms were cast for strength and ASR tests respectively. One mix was selected for SEM examination.

Figure 5.16. Samples of semi dry cast non-BS product Sub-Project 19 – Exposed Aggregate Demonstration Panels

White cement, various grades of amber, green, flint and blue glass were used to make exposed aggregate panels by Trent Concrete Ltd in Nottingham, Figure 5.17.

Figure 5.17. Deep acid-etched concrete surface finished Sub-Project 20 – Semi-Dry Cast Roof Tiles

1-3mm green sand, 1.18mm-dust flint sand, green/amber glass pozzolan (80% GP passing 35µm and 80% AP passing 75µm) were used in semi-dry cast concrete roof tiles at full scale facilities of CRH Group – Forticrete, in Leighton Buzzard, Figure 5.18. Seven concrete mixes were cast including one control mix using OPC and normal


aggregate. For each mix, a number of roof tile were cast for strength and type tests, two 75 75 280 mm prisms were cast at CCC for ASR test. One mix was selected for SEM examination and two for XRD.

Figure 5.18. Samples of semi dry cast concrete roof tiles

5.6 Results and Discussion A complete set of all sub-projects results is given in Appendix C. The main findings of the sub-project study are discussed in the following sections. 5.6.1 ASR

ASR test results up to 52 weeks show that the vast majority of the concrete products tested exhibit zero ASR expansion (a typical ASR set of results is shown in Figure 5.19, sub-project 20). Only two of the 98 mixes have exceeded BS 812-123 test criteria. Of these two mixes one used high alkali cement (Figure 5.20, sub-project 8) and one was made in an environment where control was suspect and some contamination with magnesium was found (see Figure AC.1 in Appendix C).

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0 4 8 12 16 20 24 28 32 36 40 44 48 52Age at Weeks

Exp

ansi

on (%

) PC/Ctrl. PC/GP10PC/GP20 PC/AP10PC/AP20 PC/GGS17PC/FGS17

Figure 5.19. Sample of ASR results tested to BS 812-123 of semi-dry cast concrete roof tiles (sub-project 20)

5.6.2 Product Compliance Testing

From the results shown in Appendix C, it can be seen that most of the concrete products tested performed well in product specific compliance tests. A slight reduction in strength was observed for some products, however it is felt that by making simple adjustments to the mix proportions, matching strength could easily be attained.

BS 812 test limits at 52 weeks


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HAPC/Ctrl.HAPC/GP10HAPC/GP10/GGAHAPC/GP10/FGAHAPC/GP10/AGA

Figure 5.20. Sample of ASR results tested to BS 812-123 of wet cast concrete products using high alkali cement (sub-project 8)

The compressive strength development of the ready-mixed concrete trials using GP and green glass sand (GGS) clearly shows the pozzolanic nature of GP. In Figure 5.21(a), the early-age strength of GP concrete mixes is lower than control, but after 28 days, the GP concrete gains strength at a higher rate, which is typical of pozzolanas. At a test age of 364 days, apart from GP50 mix, the strength of all the GP mixes is equal to or higher than that of the control mix. Where GP and GGS are used, Figure 5.21(b), the strength results are even more encouraging and show the pozzolanic effects of GP and also the potential benefits of using GGS.

The promising results generated in the sub-projects has lead to 3rd-party pre-certification of precast concrete products including grey blocks, paving blocks and architectural masonry [61].

5.6.3 Scanning Electron Microscope (SEM)

Scanning electron microscopy (SEM) together with EDS (energy dispersive spectroscopy) is a versatile tool which can be used to image samples easily up to 20,000x magnification and analyse the chemistry of individual areas. There are 2 common imaging modes: one is the secondary electron imaging which shows topographical differences, the other is the back-scattered electron imaging showing compositional differences. In this study back-scattered electron imaging together with EDS analysis was used to examine concrete and analyse areas of interest. All SEM images are shown in Figures in Appendix C. Ordinary Portland Cement Concrete

A typical SEM image of concrete sample with unaffected glass sand particles and fully consumed fine glass particle is shown in Figure 5.22. In this examination a 1-3mm green glass sand showed no ASR, Figure 5.22(a). However, in Figure 5.22(b), a halo of reacted materials was present around a 35µm particle. Analysis of the reacted material showed that it was rich in potassium and depleted in sodium when compared to the glass particle, indicating possible pozzolanic reaction with potassium instead of the usual calcium.

BS 812 test limits at 52 weeks


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(b)

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ngth

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)

PC Control PC/GGS50

PC/GP10/GGS50 PC/GP25/GGS50

PC/GGBS25/GP25/GGS50 PC/MS10/GGS50

Figure 5.21. Compressive strength development of ready mixed concrete containing

(a) green glass pozzolan (GP) and (b) GP and 1-3mm green glass sand

Figure 5.22. Back-scattered electron image of ready-mixed concrete using 25% green pozzolan and 50% green glass sand (sub-project 13)

Un-reacted 1-3mm glass sand

Fully consumed fine glass particles (~20µm), reaction product rich in

K, possible pozzolanic reaction

(a) (b)


High Alkali Cement Concrete

A non-typical SEM image of a concrete sample showing ASR, together with EDS spectra of the ASR gel and the glass particle are shown in Figure 5.23. In this examination many of the coarse aggregate glass grains were found to be affected by ASR type gels as expected (this sample was found to have failed the ASR test – i.e. 0.309% expansion at 52 weeks) and large cracks can be seen on the image, Figure 5.23(a). The gels appeared to be rich in potassium and calcium and slightly depleted in sodium when compared to the glass particle, Figure 5.23(b). A measurement of the gel showed it to be <100µm thick. This sample was made using high alkali Portland cement without any suppressant material and as such it was expected to form expanding ASR type gels.

Figure 5.23. (a) Low magnification back-scattered electron image of wet cast flags using HAPC, 10% green pozzolan and 100% 6-12mm amber aggregate, (b) EDS spectra of gel and glass particle (sub-project 8)

5.6.4 X-Ray Diffraction (XRD) Analysis

XRD is a common method used to identify the polycrystalline phases of cement and hardened cement paste by the recognition of unique diffracted X-ray patterns for each of various crystalline phases. The technique allows the detection of crystaline phases including quartz, calcite, portlandite and ettringite. In this research study, emphases were placed on comparing the portlandite levels between control and glass pozzolan concrete, Table 5.3. All results are shown in Appendix C, but Figure 5.24 is typical of the XRD pattern found in this study. After 1 year accelerated test conditions (38oC, RH >98%), both the control and GP mixes contain detectable portlandite with the control system having a higher peak intensity than the glass pozzolan system. This may

ASR gel

Glass grain

ASR induced crack

(a)

(b)


suggest some portlandite has been consumed by pozzolanic reaction of the glass in concrete, which would confirm the results found in sub-projects 12 and 13, where a high degree of pozzolanic reaction was observed.

Sub-Project 12

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nsity

OPC/Ctrl

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Portlandite1 0 1

Figure 5.24. XRD pattern of the portlandite of ready-mixed concrete with and without glass pozzolan (sub-project 12)


Chapter 6. Laboratory ASR Study

As an extension to the original proposed ConGlassCrete I Project, a wide ASR laboratory study was conducted at the CCC. The effect of glass colour, particle size, pozzolanic materials and cement alkali levels on glass ASR reactivity have been assessed and are described in the following sections.

6.1 Materials 6.1.1 Cement

Ordinary Portland cement (OPC, Na2Oeq: 0.62%), high alkali Portland cement (HAPC, Na2Oeq: 1.08%) and white cement (WPC, Na2Oeq: 0.17%) (supplied by Castle Cement Ltd to BS EN197 [62]) were used throughout the study. 6.1.2 Glass Cullet

Various colours and particle sizes of post-consumer glass cullet, supplied by Northern Cullet Ltd as clean sources and Valpak Ltd as contaminated sources, were used, Table 6.1.

Table 6.1. Details of the glass cullet used in the laboratory ASR study

COLOURS PARTICLE SIZE RANGE STUDY

6-12 mm Pessimum size, colour effect 3-6mm Pessimum size, colour effect

1-3mm Pessimum size

Sub 600 µm Pessimum size


Green


6-12 mm Pessimum size and colour effect, suppressants3-6mm Pessimum colour and size

1-3mm Pessimum size

300-600 µm Pessimum size


Amber


6-12 mm Pessimum colour and size 3-6mm Pessimum size and colour effect, suppressants

1-3mm Pessimum size

0.6-1.18 mm Pessimum size



Flint


6-12 mm Pessimum colour and size 3-6mm Pessimum colour and size, suppressants Blue 1-3mm Pessimum size

Mixed colour Sub 12 mm Suppressants

Mixed colour Sub 3 mm Suppressants

2.36-4.75 mm1.18-2.36 mm

0.6-1.18 mm

300-600 µm

Amber, flint and blue

150-300 µm

Comparison of ASTM C 1260, ASTM C 227 and modified ASR test methods


6.1.3 Control Aggregate

Non-reactive 5-10mm coarse aggregate and sand from Trent Valley were used in the control mixes. 6.1.4 Potential ASR Suppressants

A wide range of potential ASR suppressants were investigated, including BS 3892 [63], BS EN450 [64] and ultra-fine PFA, GGBS [65], MS (micro-silica), MK (Metakaolin) and green/amber/flint glass pozzolan (of different finenesses).

6.2 Mix Proportions 6.2.1 Effect of Glass Colour

The aim of this investigation was to determine the effect of glass colour on ASR reactivity. BS 812:123 mix proportions were used with 100% coarse glass aggregate (3-6mm and 6-12mm) and normal sand.

6.2.2 Pessimum Glass Particle Size

A range of particle sizes from sub 35µm to 12mm of green, amber, blue and flint glass cullet were used to investigate the effect of glass particle size. BS 812:123-99 mix proportions were used with 30% glass aggregate replacement for normal aggregate. 6.2.3 ASR Suppressants

ASR suppressants were used selectively in combination with the worst-case glass particle sizes. BS 812:123-99 mix proportions were used with 100% coarse glass aggregate (3-6mm and 6-12mm) and normal sand. 6.2.4 Post Consumer Glass Samples

Two sources of post consumer glass were tested, one from pub and club collection (PCC) and one from bottle bank collection (BBC). Nine concrete mixes were cast using Metakaolin (MK) and SPFA (super-classified PFA) as suppressants. BS 812:123-99 mix proportions were used with 100% coarse and fine glass aggregate. 6.2.5 ASR Testing to ASTM C1260 and ASTM C227

47 mortar mixes were cast for ASR studies to ASTM C1260, C227 and some Sheffield-modified test conditions. OPC, high alkali cement (HAPC) and white cement (WPC) were used to determine the effect of alkali content on ASR expansion. The effect of test methods, including ASTM C1260, ASTM C227 and Sheffield-modified test conditions (high temperature - 60 & 80oC and high relative humidity - RH>98%) has been assessed. BS 3892 PFA and BS EN 450 PFA (CPFA), green glass pozzolan and GGBS were used as ASR suppressants at various mass replacements. Glass types used were amber, flint and blue. Suppressants were used on an equal mass replacement basis for cement.

6.3 Test Methods The test methods used include BS 812-123, ASTM C1260 and ASTM C227. Modified test conditions were also investigated, including high temperature (60 & 80oC) and high relative humidity (RH>98%). In addition, selected ASR samples have been tested using scanning electron microscopy (SEM) to investigate the microstructure development of glass concrete after monitored to ASTM C1260 (1N NaOH solution at 80oC) and ASTM C227 (38oC, RH >98%) test conditions at different ages.

6.4 Results and Discussion 6.4.1 ASR

Glass Colour Reactivity

Figure 6.1 shows selected ASR reactivity results for 3-6 and 6-12 mm green, amber, flint and blue glass aggregate. These shows that 3-6mm blue glass appears to be most reactive, followed by 6-12mm amber and then flint glass.


3-6mm Glass Aggregate

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Figure 6.1. Effect of glass colour on 3-6 & 6-12mm glass aggregate ASR reactivity (ASTM C1260 test)

Pessimum Glass Particle Size

Summary ASR expansion results to ASTM C1260 test conditions up to 189 days for a range of particle sizes from less than 40µm to 12mm of green, flint, amber and blue glass used as aggregate in concrete are shown plotted in Figures 6.2-6.5. It can be seen that for green, flint and amber colour, when the glass particle size is less than or equal to the <0.6mm and 0.6-1.18mm range respectively, the expansion is less than the control aggregate concrete mix, implying that some degree of ASR suppression is gained by the use of fine glass particles. The trend for blue glass is opposite to that found with other glass colours, Figure 6.5, in that ASR expansion increases with decreasing particle size.

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Figure 6.2. Effect of green glass particle size on ASR reactivity (ASTM C1260 test)


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Figure 6.3. Effect of flint glass particle size on ASR reactivity (ASTM C1260 test)

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Figure 6.4. Effect of amber glass particle size on ASR reactivity (ASTM C1260 test)


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Figure 6.5. Effect of blue glass particle size on ASR reactivity (ASTM C1260 test) Potential ASR Suppressants

The ASR expansion results of concrete made with a range of potential ASR suppressants are shown plotted in Figures 6.6-6.9. These show that metakaolin (MK), pulverized-fuel ash (PFA) and GGBS could potentially mitigate ASR expansion. Other materials tested, including WPC, micro silica (MS) and ground glass at around 300m2/kg, also reduce ASR expansion significantly.

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Figure 6.6. ASR expansion of concrete made with MK, green glass pozzolan (GP) and 3-6mm flint glass aggregate (ASTM C1260)


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Figure 6.7. ASR expansion of concrete made with various ASR suppressants and 6-12mm amber glass aggregate (ASTM C1260)

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Figure 6.8. ASR expansion of concrete made with various ASR suppressants and 3-6mm blue glass aggregate (ASTM C1260)


Blue with HAPC and GGBS

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Figure 6.9. ASR expansion of mortar made with HAPC, different replacement levels of GGBS and blue glass aggregate (ASTM C227)

Post-Consumer Glass Cullet

ASR expansion results for unwashed and washed post-consumer glass cullet collected from pub & club (P&C) and bottle banks (BB) are shown in Figures 6.9 and 6.10 and show generally similar trends to clean glass sources. However, unwashed post-consumer BB cullet appears to be more expansive than washed BB cullet (Figure 6.10). As with the clean glass sources, however, both SPFA and MK effectively mitigate ASR effects.

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Figure 6.9. Expansion results for concrete made with MK, SPFA and P&C cullet

ASTMC227 TEST LIMITS AT 26 WEEKS


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Figure 6.10. Expansion results for concrete made with MK, SPFA and BB cullet ASTM ASR Mixes

Tables AD.1 and AD.2 in Appendix D detail the ASR test results from a strict ASTM test regime using WPC, OPC and HAPC. According to ASTM C1260, expansions of less than 0.1% at 14 days are indicative of innocuous behaviour, 0.1-0.2% at 14 days suggest potentially deleterious behaviour and >0.2% indicate reactive aggregate. Almost all the mixes tested to date have passed the ASTM C1260 criteria. However, emerging work in this project and elsewhere [66] suggests that the C1260 test may be inappropriate for testing glass and pozzolanic systems and therefore more work has been carried out at Sheffield using the ASTM C227 and modified test conditions including high temperature (60 & 80oC) and high relative humidity (>98%) to give additional confidence to these findings. According to ASTM C227, expansions of less than 0.05% at 3 months and 0.1% at 6 months are indicative of innocuous behaviour. Only 5 out of 47 mortar mixes have failed the C227 test. These all contained high alkali cement, Table AD.2. All of the unaffected specimens listed in Appendix D are continuing to be tested at Sheffield.

6.4.2 Scanning Electron Microscope (SEM) SEM images of selected laboratory ASR samples and a brief discussion of these are given in the following sections. Samples subjected to ASTM C1260

Laboratory ASR samples with highest expansion were selected for SEM examination to determine the position of the ASR gel and its density. These images are shown in Figures 6.11-6.14, where it can be seen that all samples examined have ASR gel present. This is not surprising because of the very severe accelerated conditions (1N NaOH solution at 80oC for up to 49 days). Optically, the samples appeared to have a reaction phase around each of the glass grains (present as a white outer layer), but this was not confirmed by SEM. It is therefore likely that this outer reaction layer is extremely thin and may be removed during sample preparation. The main ASR reactions were seen in cracks and fissures in the glass grains. It is likely that ASR gel is formed faster at high stress concentrations and when it hydrates and swells, the glass grain fails under tension. It should be noted that most of the ASR cracks are seen passing through glass particles and this suggests that ASR starts in existing micro-cracks that were formed during glass crushing process, and then proceeds deeper into the particles as the crack extends.


Figure 6.11. Back-scattered electron image of OPC/AGA6-12 – 28 days in 1N NaOH solution at 80oC, (a) low magnification and (b) high magnification

Figure 6.12. Back-scattered electron image of OPC/FGA6-12 – 28 days in 1N NaOH solution at 80oC, (a) low magnification and (b) high magnification

Figure 6.13. Back-scattered electron image of OPC/BGA3-6 – 49 days in 1N NaOH solution at 80oC, (a) low magnification and (b) high magnification

K-enriched ASR gel, cracks through glass particles

Unexpanded cracks

K-enriched ASR gel in cracks through

glass particles

K-enriched ASR gel in glass

particles

Glass

Ca-enriched ASR gel

Glass

C-S-H

(b) (a)

(a) (b)

(a) (b)


Figure 6.14. Back-scattered electron image of WPC/BGA3-6 – 49 days in 1N NaOH solution at 80oC, (a) low magnification and (b) high magnification Comparing the images of WPC concrete (Figure 6.14) to that of OPC concrete (Figure 6.13), it can be seen that the number and thickness of the ASR cracks for the same 3-6mm blue glass aggregate are very much reduced with WPC. This confirms the findings in other areas of this study, that the cement alkali level is a major factor in the rate of ASR. EDS examination of the ASR gels shows that they are mainly glassy material, enriched with calcium, sodium or potassium. This suggests that the mechanism of ASR involves localised diffusion of these ions within the system (both from the glass and from the cement) probably combined with attack of the silica network by alkaline solution (glass is vulnerable to corrosion at pH above 9.5). Samples subjected to ASTM C227

ASR samples made following a strict ASTM C227 test regime and tested to C227 conditions (38oC and RH >98%) were selected for SEM examination to investigate the effectiveness of different potential ASR suppressants. Images of high alkali cement and glass cullet mortar without suppressants are shown in Figures 6.15-6.16 and images of samples containing PFA and CPFA as 30% replacement of cement are shown in Figures 6.17-6.18. It was seen from expansion measurements that HAPC/Blue had the largest expansion of all samples examined, followed by flint and then amber with expansions of 0.896%, 0.730% and 0.602% respectively at 22 weeks. In these 3 samples, Figures 6.15-6.16, most of the large glass grains and some of the smaller blue grains appeared to be affected by ASR gel. Gels of up to 100µm thickness could be seen in cracks which had formed within the glass fragments. In addition, large scale cracking of the cement paste was evident, indicating that the integrity of the concrete had been compromised. The gel was found to be rich in both potassium and calcium, but depleted in sodium compared to glass, Figure 6.15(b). Close examination of a sample containing CPFA showed the presence of ASR gels in a few of the larger blue glass particles and two of the larger flint and amber glass particles. The thickness of these gels was found to be <10µm and these were within cracks in the glass aggregate, Figures 6.17 and 6.18(a). Analysis of the gels indicated that they were rich in potassium and slightly depleted in sodium when compared to glass. Comparing these images against those of samples without any suppressants (Figures 6.15-6.16), it is very clear that CPFA is extremely effective at mitigating ASR reaction of blue, flint and amber glass aggregate. A close examination of a sample containing PFA showed the possible presence of an ASR-type gel in only one of the larger particles, Figure 6.18(b). The quantity of gel available, if indeed it was ASR gel, was too small to analyse and this confirms the very high effectiveness of PFA as an ASR suppressant [compare to Figure 6.16(a)].

K and Ca enriched ASR gel

(b) (a)


Figure 6.15. (a) Back-scattered electron image of HAPC/Blue – 22 weeks treatment and (b) EDS spectra of gel in glass particle

Figure 6.16. Back-scattered electron image of samples after 22 weeks treatment, (a) HAPC/Flint and (b) HAPC/Amber

(a)

(b)

(a) (b)


(a) (b)

Figure 6.17. Back-scattered electron image of samples after 22 weeks treatment, (a) HAPC/CPFA30/Blue and (b) HAPC/CPFA30/Amber

(a) (b)

Figure 6.18. Back-scattered electron image of samples at 18 weeks treatment,

(a) HAPC/CPFA30/Flint and (b) HAPC/PFA30/Flint

6.5 Architectural Concrete Finishes Over 30 architectural concrete finishes have been developed in laboratory. These are made from white cement with various pigment and glass aggregates with different colours and grades, Figures 6.19-6.24.


Figure 6.19. Architectural concrete finishes – amber glass in various pigments


Figure 6.20. Architectural concrete finishes – amber and blue glass in various pigments


Figure 6.21. Architectural concrete finishes – blue glass in various pigments


Figure 6.22. Architectural concrete finishes – flint glass in various pigments


Figure 6.23. Architectural concrete finishes – green glass in various pigments


Figure 6.24. Architectural concrete finishes – blue, flint and green glass in various pigments


Chapter 7. Specifications for Waste Glass as a Pozzolan and an Aggregate in Concrete 7.1 Introduction These tentative specifications are intended to apply to the waste glasses indicated in the scope of each specification. Borosilicate and CRT glass have not been studied and are specifically excluded. These specifications should be read as tentative until longer-term testing of the ASR performance of glass in cementitious systems has been conducted and reported. To that end, the University of Sheffield has the following libraries of specimens under long-term test as follows: i) over 100 real concrete products containing glass as aggregate and powder from the industrial sub-projects that formed part of this project (see Table 5.1); ii) over 150 concrete mixes cast as part of the parametric laboratory study that formed part of this project (see Tables AD.1 and AD.2) and iii) a series of mixes designed to determine the effects of variable alkali content in Portland cements and the influence of cement replacement materials on the rate of ASR in large-scale specimens exposed to outdoor conditions. These samples are stored at the Building Research Establishment [69, 70].

7.2 Specification for Use of Glass as a Pozzolan in Concrete, Mortar

or Grout 7.2.1 Scope

This specification refers to powdered container, plate or lighting glass intended for use as a cement replacement material in concrete, mortars or grouts. No specification is given on particle size, but the surface area should comply with Clauses 7.2.3.7. 7.2.2 Background

The requirements for powdered glass addressed in this specification are related to factors that may affect the setting time, rate of hardening or durability in cementitious systems or the potential for an environmental health hazard. Tentative values for these parameters and the appropriate British Standard test methods are given in the following clauses, which have been established from: i) an examination of the specifications for fly ash, BS EN 450 [64] and BS 3892 [63] and natural pozzolans ASTM C331-02 [71] for use in concrete; ii) analysis of the results of 19 precast concrete sub-projects in which over 100 concrete mixes were tested for up to 1 year for engineering and durability properties; iii) extensive characterisation and strength testing of raw glass powder materials in the ConGlassCrete II Project [61]; iv) 3rd-Party testing of the results obtained at the University of Sheffield by a UKAS-accredited laboratory, under the supervision of BRE [72]. v) Pre-certification of the material specifications given below in Clauses 7.2.3 [73].


7.2.3 Specification Clauses

7.2.3.1 Health and Safety

Protective clothing including gloves and a dust mask should be worn. Care should be taken not to inhale fine particles of glass in any circumstances. There is danger of cutting injury from larger glass particles that have been split or broken by impact during storage – in the case of injury seek medical help. In the case of eye-contact, wash out the eye and seek medical help. 7.2.3.2 Silica content

The proposed minimum silica content for glass pozzolan is 68%. The average silica content of clean container, plate and lighting glass is around 70%. The specified lower value allows for slight material variation and contamination as is found in post-consumer glass e.g. from bottle banks and pub and club collections [61]. 7.2.3.3 Fe2O3, Al2O3, Na2O, K2O, CaO and MgO

The contents of these compounds should be supplied as a further check on material chemistry. 7.2.3.4 Chloride content

The chloride ion content shall not be more than 0.1%, in line with the values for slag and PFA in BS 6699 [65] and BSEN 450 [64]. This value ensures that the powdered glass will not adversely affect the durability of steel reinforcing bars in concrete. 7.2.3.5 Sulfur trioxide (SO3)

The SO3 content shall not be higher than 3% [64]. 7.2.3.6 Loss on ignition (LOI)

The LOI should not be higher than 1.5%. This value is the upper limit detected in a wide- ranging study [70] of the allowable waste glass streams and has not been found to be detrimental to the setting time of cementitious combinations made with 30% ground glass pozzolana. 7.2.3.7 Surface Area

The surface area shall not be less than 300m2/kg. A major study [61], the results of which have been certified by BRE [72] and checked in a UKAS-accredited laboratory [73], has determined that this minimum fineness is required in order for ground glass pozzolana to reach an Activity Index equivalent to a BSEN450 fly ash. 7.2.3.8 Activity Index

The Activity Index shall not be less than 75% at 28 days and 85% at 90 days [64]. 7.2.3.9 Soundness

The soundness, when measured to BS EN 196-3 [74], shall not exceed 10mm. 7.2.3.10 Setting Time

The maximum initial setting time, when measured to BS EN 196-3 [74], shall be 2 hours more than the control cement. This value is slightly greater than the highest found in over 30 glass samples from different sources [61], all of which performed at an acceptable level in concrete. 7.2.3.11 Lead Content

The maximum lead content is limited to 0.1% to prevent retardation [75]. This value ensures that CRT screens are excluded from the source material. 7.2.4 Production

Producers of glass pozzolan for use in concrete shall operate their process such that the material produced complies with the Clauses in Section 7.2.3 of this specification. Producers shall carry out the minimum sampling frequencies shown in Table 7.1. Each time material from a new source is being processed, the sequence in Table 7.1 should commence from Stage 1.


Table 7.1. Minimum Sampling and Testing Frequencies

FREQUENCY TEST Stage 1 – Until statistical

variability is defined* Stage 2 – thereafter

Oxides

2/day

1/day

Chloride 1/day 2/week SO3 1/day 1/week LOI 1/day 2/week Fineness 2/day 1/day Activity Index 1/day 2/week Soundness 2/week 1/week Setting Time 1/day 1/week Lead 1/day 1/week

*The duration of Stage 1 is the responsibility of the producer and will be related to the consistency of the raw materials being processed.

7.2.5 Conformity

The values given in Clauses 7.2.3 are in all cases the maximum acceptable for any individual load. 7.2.6 Information to be Supplied by Producer on Request

The following information must be supplied by the producer to the purchaser, on request:

i) A copy of this specification

ii) The mean and variability of the last 35 measurements of all parameters in Table 7.1

7.2.7 Marking and Labelling

Each load of glass pozzolan shall have a delivery ticket attached containing the following information:

i) Glass pozzolan to ConGlassCrete specification

ii) Supplier’s name

iii) Purchaser’s name

iv) Date of supply

v) BRE Certification Reference [72, 73]

7.3 Specification for the Use of Glass as an Aggregate in Concrete 7.3.1 Scope

This specification refers to crushed container or plate glass with a particle size greater than 1mm that is intended for use as a fine or coarse aggregate in mortars or concrete. It should be noted that glass aggregates can react with alkali in concrete and the responsibility for ensuring that this does not happen rests with the designer of the concrete, not with the supplier of the glass aggregates nor the writers of this specification. 7.3.2 Background

The requirements for fine or coarse glass aggregate in this specification are related to factors that may affect the setting time, rate of hardening or durability in cementitious systems or the potential to cause an environmental health hazard. Tentative values for quality control parameters are given in the following Clauses, which have been established from: i) analysis of the results of 19 precast concrete sub-projects in which over 100 concrete mixes were tested for up to 1 year for engineering and durability properties and ii) extensive testing of glass as aggregate in concrete as part of the laboratory study of this Project.


7.3.3 Specification Clauses

7.3.3.1 Health and Safety

Protective clothing including gloves and a dust mask should be worn. Care should be taken not to inhale fine particles of glass in any circumstances. There is danger of cutting injury from larger glass particles that have been split or broken by impact during storage – in the case of injury seek medical help. In the case of eye-contact, wash out the eye and seek medical help. 7.3.3.2 Grading

The producer shall state the grading of the aggregate offered for sale on demand. 7.3.3.3 Setting Time

The glass aggregates shall not contain any substance that will increase the setting time of concrete by more than 2 hours [76] 7.3.3.4 Influence on Compressive Strength

The glass aggregates shall not contain any substance that decreases the compressive strength of concrete by more than 10 [76]. 7.3.3.5 Chloride Content

The glass aggregates shall have a surface chloride contamination of less than 0.01% [76] 7.3.3.5 Sulfur Trioxide

The glass aggregates shall have a sulfur trioxide level of less than 0.1% [76] 7.3.4 Production

Producers of glass aggregates for use in concrete shall operate their process such that the material produced complies with the Clauses in Section 7.3.3 of this specification. Producers shall carry out the minimum sampling frequencies shown in Table 7.2. Each time material from a new source is being processed, the sequence in Table 7.2 should commence from Stage 1.

Table 7.2. Minimum Sampling and Testing Frequencies

FREQUENCY TEST Stage 1 – Until statistical

variability is defined* Stage 2 – thereafter

Grading

2/day

1/day

Setting Time 1/day 2/week Compressive Strength

1/day 1/week

Chloride 1/day 2/week Sulfur trioxide 2/day 1/day Lead 1/day 1/week

*The duration of Stage 1 is the responsibility of the producer and will be related to the consistency of the raw materials supplied.

7.3.5 Conformity

The values given in Clauses 7.3.3 are in all cases the maximum acceptable for any individual load. 7.3.6 Information to be Supplied by Producer on Request

The following information must be supplied by the producer to the purchaser, on request:

i) A copy of this specification

ii) The mean and variability of the last 35 measurements of all parameters in Table 7.2


7.3.7 Marking and Labelling

Each load of glass pozzolan shall have a delivery ticket attached containing the following information:

i) Glass aggregate to ConGlassCrete specification

ii) Supplier’s name

iii) Purchaser’s name

iv) Date of supply

v) Reference to any Certification document


Chapter 8. National Cullet Usage Data 8.1 Total Cullet Availability The ConGlassCrete I Project has carried out a material scoping exercise to assess the current available tonnages of container glass and, where possible, to encourage working partnerships to create additional demand. Table 4.1 and 4.2 show the latest published data on UK production, importation, exportation and consumption and the arisings and recovery of container glass respectively. The importation and exportation percentages have been estimated from the assumption that most imports are green wine and beer bottles and most of the exports are clear whisky bottles [67].

Table 4.1. UK Production, importation and exportation of container glass in 2001

PRODUCTION IMPORTATION EXPORTATION CONSUMPTION GLASS COLOUR

103tonnes/year %b 103tonnes/year%d 103tonnes/year%d 103tonnes/year

Green 323 19 1,039 90 1335

Amber 272 16 -53 10

303

Flint 1,105 65 115 10

-472 90 691

TOTAL +1,700a +1,154c -525e 2,329

a, c, e The source of all these data was British Glass. Biffa Programme on sustainable resource use. Available from URL www.britglass.co.uk/files/documents/BIFFAReport_09012004153824.pdf

b. WRAP. Developing Markets for Recycling Glass [68]

d Estimated based on type of UK imports and exports [67]

In Table 4.2 the potential arisings for container glass have been estimated from a sorting study carried out on bottle bank samples at the CCC. The recovery figures were obtained from literature [68].

From these it can be seen that the current cullet recovery in the UK is just under 40% of the total consumption at around 750,000 tonnes.

Table 4.2. UK consumption, arisings and recovery of container glass

CONSUMPTION 2001 ARISINGS 2002 RECOVERY 2002 GLASS COLOUR

103tonnes/year % 103tonnes/year % 103tonnes/year %b

RECYCLING RATE

Green 1335 57 1320 60 388 52 29.4

Amber 303 13 286 13 105 14 36.7

Flint 691 30 528 24 254 34 48.8

Other - 66 3 No data No data No data

TOTAL 2,329 2,200a 747a 38.3

a WRAP. Recycling Glass Market Study & Standards Review [7]

b WRAP. Developing Markets for Recycling Glass Presentation [68]


8.2 Cullet Available to the Concrete Sector The Waste Officer of every Local Authority (487 Authorities) in the country was contacted by e-mail as part of this porject. The email queried: i) the status of glass recycling in their area of responsibility and what existing provisions were in place with respect to future glass recycling contracts and ii) if the LA could foresee the need to make alternative arrangements for recycled glass materials as collection targets rose. Responses were not encouraging, despite the fact that one of the project’s precast concrete partners was willing to discuss setting up a glass recycling centre if the economics were favourable. The majority of Local Authorities who responded perceive, at least within the current framework of fiscal responsibilities, that concrete construction is a lower value end use of waste glass than other sectors. It is concluded from this that: i) use of waste glass as a low-grade filler, fine or coarse concrete aggregate may not be a viable option for new investment in the short term as recent stimulation of the market by Government funding has created a significantly higher demand than when this project was conceived. ii) as collection rates rise the price is likely to drop, particularly if the cullet is mixed. The markets referred to in i) above may then become more viable. iii) the higher-value applications of glass in concrete, such as cement replacement materials, specialist and standard sands and decorative exposed aggregate finishes almost certainly have markets in concrete, but future work is needed to take these products to market.


Chapter 9. Conclusions

1. The most significant barriers to increasing glass recycling into the concrete construction industry are low collection rates and competition for the material by higher-value markets. It is envisaged that this will change as EU Directives take force over the next 2 years.

2. Tests at the University of Sheffield have shown that glass as both pozzolan and aggregate can perform adequately in ready-mixed concrete and in a range of precast concrete products up to one year of age;

3. Up to one year of age, zero ASR expansion was observed in a series of over 100 glass pozzolan and/or glass aggregate precast concrete products except where high alkali cement was used. This was confirmed by both physical and chemical tests;

4. Cement alkali content is the most significant influence on the rate of ASR of glass in concrete;

5. The relative effects of glass colour on ASR reactivity were not clear and appeared to change with particle size. It may be, given that ASR is initiated in microcracks, that glass crushing technique is more significant than colour, which is effected only by tiny chemical changes;

6. 30% BS3892 or BS EN450 PFA, 40% GGBS or 20% MK seems to mitigate ASR of glass in concrete, at least up to one year in accelerated conditions;

7. The reactivity of glass particles generally increases with particle size from around 1-2mm. Glass particles below this size appear to reduce the propensity for ASR in larger glass particles;

8. Ready-mixed concrete made with glass pozzolan and/or glass sand shows increasing strength development to 1 year, indicating a pozzolanic contribution from the fine glass particles;

9. Whilst the highest possible confidence (compliance with British Standards) applies to the ASR test results of this project, the nature of ASR is such that extended testing of the library of over 200 concrete mixes at Sheffield is highly recommended.

10. The price of cullet in the current market is probably prohibitive to new industrial investment in cullet for low-value filler, fine or coarse aggregates in concrete. The higher value markets, such as glass as pozzolan and glass as decorative aggregate are significantly more financially attractive. These are likely to be the primary uses of cullet within concrete construction until fiscal measures and collection rates make lower value uses more viable.


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Documents

CONGLASSCRETE I - …webarchive.nationalarchives.gov.uk/20100503135839/http:/wrap.org...5.4 Test Methods 12 5.5 Sub-Project Descriptions 13 5.6 Results and Discussion 21 5.6.1 ASR