DEVELOPMENT AND ASSESSMENT OF ALKALI ACTIVATED RECYCLED GLASS-BASED CONCRETES FOR CIVIL INFRASTRUCTURE

DEVELOPMENT AND ASSESSMENT OF ALKALI ACTIVATED RECYCLED GLASS-BASED CONCRETES FOR CIVIL INFRASTRUCTURE

ABSTRACT

Beneficial utilization of recycled glass powder (GP) as a supplementary cementitious material has been limited due to the poor knowledge of the interactions between GP and concrete environment. For example, it is seen that the early-age strength of concrete is reduced. This is attributed to the slow rate of GP pozzolanic reaction which begins with dissolution of glass. The hypothesis of this research is that GP dissolution and hence its reactivity can be accelerated by increasing the alkalinity of pore solution. The core objective of this research is to evaluate this hypothesis through a step-by-step experimental method, designed to answer four specific questions: (1) what are the chemical and physical aspects of soda-lime glass dissolution in alkaline solution? (2) Does reactivity of GP with Ca(OH)₂ accelerate through use of alkaline solutions? (3) What is the overall performance of concrete, containing GP and mixed using alkaline solutions? (4) What are the micro-scale mechanical properties of the cementitious products of GP in concrete in comparison to conventional cementitious materials?

To answer the first question, this research conducts a fundamental analysis of the interactions between soda-lime glass and concentrated NaOH solutions. Along with

measurement of the kinetic parameters of glass dissolution, the characteristics of solid products forming as a consequence of soda-lime glass dissolution is studied using characterization techniques. It is shown that 1M NaOH solution is more corrosive than other concentrations, with activation energy of dissolution measured as ≈85 kJ/mole. Addition of Ca(OH)₂ to 1M NaOH solution decreases the rate of glass dissolution. It is also found that due to the presence of calcium in soda-lime glass, dissolution is accompanied by formation of semi-crystalline calcium silicate hydrate (C-S-H) materials.

To answer the second question, pastes of GP-Ca(OH)₂ are prepared by mixing with water or  NaOH solutions and the reaction rate, stoichiometry and characteristics of the reaction products between GP and Ca(OH)₂ are investigated. It is concluded that NaOH solution can significantly accelerate the rate of the reaction between GP and Ca(OH)₂ to form C-S-H products.

To answer the third question, the compressive strength of four mortar systems containing GP are evaluated, focusing on the use of alkaline solutions. These include mortars prepared by the binary phases of GP-Ca(OH)_2, GP-portland cement(PC), GP-slag and GP-fly ash. While alkaline solutions are helpful in the first system, the low absolute strength values limit its application. Also, due to a severe detrimental effect of alkaline solutions on hydration of PC, the use of alkaline solution in PC-based systems is not justified. However, due to compatibility of slag and fly ash to alkaline solution, these systems are found to be appropriate host concretes for GP, enriching the binding phases with silica.

Finally, micro-scale mechanical properties of the cementitious phase formed due to pozzolanic reaction of glass is studied using peak force tapping AFM, and compared to hydration products of PC, alkali activated slag and fly ash systems. Due to the very small induced deformation (3-5nm), surface topography becomes super critical. The measured modulus values are lower than the available literature data, usually assessed using conventional indentation techniques.

 

 

Table of Contents

 

List of Figures……………………………………………………………………………………………………………….. xi 

List of Tables……………………………………………………………………………………………………………… xviii

 

Acknowledgements ……………………………………………………………………………………………………….. xx

Chapter 1 : Introduction …………………………………………………………………………………………………… 1

1.1.Sustainability in concrete …………………………………………………………………………………….. 1

1.2.The Importance of research on using recycled glass in concrete ……………………………….. 2

1.3.Pozzolanic reaction (PR) of glass powder………………………………………………………………. 6

1.4.Alkali silica reaction (ASR) of glass cullet …………………………………………………………… 10

1.5.Research objectives …………………………………………………………………………………………… 11

1.6.Tasks and organization of the contents ………………………………………………………………… 13

1.7.References ……………………………………………………………………………………………………….. 16

Chapter 2 : Earlier Work on the Use of Pulverized Recycled Glass in Concrete ……………………. 18

2.1.Introduction ……………………………………………………………………………………………………… 18

2.2.Use of glass cullet as sand replacement in concrete ……………………………………………….. 18

2.3.Use of glass powder as a cementitious material …………………………………………………….. 20

2.4.Author’s previous work on ASR of recycled glass cullet ……………………………………….. 22

2.5.References ……………………………………………………………………………………………………….. 25

Chapter 3 : Study of the Dissolution of Soda-lime Glass in Alkaline Solutions, Effect of Calcium

Presence, and Characterization of Products ……………………………………………………………. 29

3.1.Introduction ……………………………………………………………………………………………………… 29

3.2.   Structure and interactions of silicate glasses with aqueous solutions ……………………….. 32

3.3. Leaching (ion exchange) ……………………………………………………………………………………. 33

3.4.Network dissolution ………………………………………………………………………………………….. 34

3.5.Research objectives …………………………………………………………………………………………… 39

3.6.Experimental work ……………………………………………………………………………………………. 40

3.6.1.      Kinetics of glass dissolution in NaOH solutions ……………………………………………. 40

3.6.1.1.      Effect of NaOH molarity and temperature on dissolution rate of SLG ……….. 40

3.6.1.2.      Effect of Ca(OH)₂ presence in 1M NaOH solution on dissolution of glass; a

comparison to pure silica glass ……………………………………………………………… 42

3.6.1.3.      Analysis of the elemental concentration of calcium and silicon in NaOH

solution ………………………………………………………………………………………………. 43

3.6.2.      Characterization of glass dissolution products ………………………………………………. 43

3.6.2.1.     SEM/EDS analysis of dissolution products of glass slides ………………………… 44

3.6.2.2.      Further SEM analysis of soda-lime glass (beads) dissolution products

(Appendix B). ……………………………………………………………………………………… 47

3.6.2.3.      XRD analysis of soda-lime glass dissolution products ……………………………… 48

3.6.2.4.      TEM analysis of glass dissolution products and glass/product interface

(prepared using FIB) ……………………………………………………………………………. 50

3.7.Results and discussions ……………………………………………………………………………………… 54

3.7.1.      Results of the kinetics of dissolution ……………………………………………………………. 54

3.7.1.1.      Effect of NaOH molarity and temperature on dissolution of SLG ……………… 54

3.7.1.2.      Effect of Ca(OH)₂ presence in NaOH solution on dissolution rate of SLG;

comparison to pure silica ……………………………………………………………………… 58

3.7.1.3.     Analysis of elemental concentrations of the solutions ………………………………. 62

3.7.2.      Results of characterization of dissolution products ………………………………………… 65

3.7.2.1.     SEM/EDS analysis of SLG dissolution products in No-Ca system …………….. 65

3.7.2.2.      SEM/EDS analysis of SLG dissolution products in SS-Ca system …………….. 69

3.7.2.3.      Corrosion products of pure silica glass in 1M NaOH ……………………………….. 73

3.7.2.4.      Characterization of dissolution products by XRD ……………………………………. 74

3.7.2.5.     TEM results ………………………………………………………………………………………… 77

3.8.Conclusions ……………………………………………………………………………………………………… 86

3.9.References ……………………………………………………………………………………………………….. 88

Chapter 4 : Effect of Alkaline Solution on the Rate and Stoichiometry of CH:GP Reaction …… 93

4.1.Introduction ……………………………………………………………………………………………………… 93

4.2.Research objectives …………………………………………………………………………………………… 94

4.3.Theoretical considerations on stoichiometry of the pozzolanic reaction …………………… 95

4.4.Experimental work ……………………………………………………………………………………………. 96

4.1.1.      Measuring the stoichiometry and rate of pozzolanic reaction ………………………….. 97

4.1.1.1.     Measurement of the unreacted Ca(OH)₂ and chemically bound water content 98

4.1.1.2.      Measurement of the glass powder consumption ………………………………………. 99

4.1.2.      Characterization of the reaction products (XRD and SEM) …………………………….. 99

4.5.Results …………………………………………………………………………………………………………… 101

4.1.3.      Quantity of the reactants and products during the pozzolanic reaction ……………. 101

4.1.4.       SEM/EDS analysis of reaction products …………………………………………………….. 107

4.1.5.      XRD analysis of the reaction products ……………………………………………………….. 113

4.1.6.      Calculating the reaction stoichiometry ……………………………………………………….. 118

4.6.   Conclusions ……………………………………………………………………………………………………. 121

4.7. References ……………………………………………………………………………………………………… 123

Chapter 5 : Use of Recycled Glass Powder in Different Cementitious Systems …………………… 126

5.1.Introduction ……………………………………………………………………………………………………. 126

5.2.Objectives ………………………………………………………………………………………………………. 126

5.3.Alkali activated slag and alkali activated fly ash binders ……………………………………… 128

5.4.Experimental work ………………………………………………………………………………………….. 129

5.4.1.      Materials ………………………………………………………………………………………………… 129

5.4.2.       Methods …………………………………………………………………………………………………. 131

5.4.2.1.      Compressive strength measurement of binary mortars (GP-PC, GP-Slag, and

GP-fly ash) ……………………………………………………………………………………….. 131

5.4.2.2.      Compressive strength of CH-GP mortars ……………………………………………… 133

5.4.2.3.      ASR expansion evaluation of alkali activated mortars ……………………………. 135

5.4.2.4.      Microstructure of AA Slag and AA Fly ash…………………………………………… 136

5.5.Results and discussions ……………………………………………………………………………………. 136

5.5.1.      Compressive strength of GP in Portland cement-based mortars …………………….. 136

5.5.2.       Compressive strength of GP in alkali activated slag-based mortars ……………….. 138

5.5.3.       Compressive strength of alkali activated fly ash-based mortars …………………….. 139

5.5.4.      Compressive strength of CH-GP mortars ……………………………………………………. 140

5.5.5.       Accelerated mortar bar expansion of alkali activated slag and fly ash containing

GP 142

5.5.6.      Microstructure SEM/EDS …………………………………………………………………………. 143

5.6.Conclusions ……………………………………………………………………………………………………. 152

5.7.   References ……………………………………………………………………………………………………… 155

Chapter 6 : Use of Peak-force Tapping Mode AFM to Measure Nano-scale Mechanical

Properties of Cementitious Materials …………………………………………………………………… 156

6.1.Introduction ……………………………………………………………………………………………………. 156

6.2.Nano-scale mechanical properties of cementitious systems (background) ………………. 156

6.3.Research objectives …………………………………………………………………………………………. 160

6.4.Experimental procedure …………………………………………………………………………………… 161

6.4.1.      Materials ………………………………………………………………………………………………… 161

6.4.2.      Procedure: ………………………………………………………………………………………………. 163

6.5.Results and discussions ……………………………………………………………………………………. 163

6.5.1.        AFM indentation analysis of OPC and glass bead pozzolanic reaction products 163

6.5.2.       AFM analysis of OPC hydration ……………………………………………………………….. 165

6.5.3.      AFM analysis of alkali activated slag …………………………………………………………. 166

6.5.4.       AFM analysis of alkali activated fly ash …………………………………………………….. 168

6.6.Discussions and conclusions …………………………………………………………………………….. 170

6.7.References ……………………………………………………………………………………………………… 171

Chapter 7 : Summary, Conclusions and Future Directions ………………………………………………… 174

7.1. Conclusions of the study of dissolution and interaction of soda-lime glass with highly

alkaline solutions …………………………………………………………………………………………….. 175

7.2. Conclusions of the study of the stoichiometry of CH-GP pozzolanic reaction and the

effects of alkaline solutions ………………………………………………………………………………. 177

7.3. Conclusions of the study on developing mortars by using recycled glass powder within

different cementitious systems ………………………………………………………………………….. 178

7.3.      Conclusions on the study of using peak-force tapping mode AFM for analysis of micro-

scale mechanical properties of cementitious phases …………………………………………….. 179

7.4. Suggestions for future work ……………………………………………………………………………… 179 Appendix A: Calculation of speciation of silica in aqueous solutions …………………………….. 182

Appendix B: SEM images of dissolution products of soda-lime glass in 1M NaOH solution184

Appendix C: Published paper ……………………………………………………………………………………. 191

Chapter 1 : Introduction

1.1.  Sustainability in concrete

Concrete is the most abundant man-made composite material. It is made of aggregates, a cementitious binder phase and water (or an aqueous liquid) as the main components. Production of portland cement in the kiln results in a significant energy use (embodied energy ≈ 5.7MJ/kg cement) and a large CO₂ footprint (approximately 0.95kg CO₂/kg cement) [1] , which accounts for approximately 5% of the global anthropogenic CO₂ emissions [2] . Therefore, in addition to performance and durability concerns, the next generation of concrete materials is required to adopt sustainable development.

Various materials and approaches have been studied in the last decades to find appropriate environmentally friendly materials to be used as partial or complete replacement of portland cement. The most important ones include blast furnace slag (by-product of steel manufacturing), fly ash (by-product of coal combustion process), silica fume, rice husk ash and natural pozzolans. Selection and incorporation of any new material as a concrete constituent should be performed with enough knowledge to assure short and long term health and performance of concrete. One of the viable materials that may be used successfully as a concrete component towards production of green concrete is recycled soda-lime glass.

1.2. The importance of research on using recycled glass in concrete

Soda-lime glass (e.g., bottles, windows) is fully recyclable at the end of its service life. It can be melted and molded into new glass products. In practice, however, this does not happen completely. According to a recent EPA report [3] , 11.6 million tons of glass was generated in the U.S. in 2012, where approximately 28% (3.2 million tons) was recovered and the rest (8.4 million tons) was discarded as municipal solid waste. The recovered glass (mostly containers) should ideally be used to make new glass products. However, in some locations (e.g., NYC, eastern PA), the costs of transporting recycled glass from collection points to remelting centers may far exceed the cost of glass production from natural siliceous sand. In addition, difficulties in color sorting and removal of contaminations (paper, sugar, etc.) impede proper recycling of glass. The result is the formation of large stockpiles of collected glass in many areas of the country (Figure 1-1 and Figure 1-2). A similar problem has been reported in Europe, Middle East, and Australia [4] . High-quality glass cullet can be used for abrasives, bead manufacturing, decorative applications, fiberglass, and fluxes in metal foundry work. Lower-quality cullet can be used in applications such as roadbed aggregate, in the manufacture of fiberglass insulation, driving safety reflective beads, and decorative tile [5] .

One of the attractive applications of recycled glass is the use as a concrete constituent. Large quantities of recycled glass could be incorporated into concrete since concrete is produced in very large volumes; U.S. production of ready-mixed concrete in 2010 was 430 million tons [6] .

There are two approaches for using glass as a concrete constituent:

1. Application of glass cullet (75 µm < Size <4.75 mm) as aggregate to replace sand.
2. Application of glass powder (Size < 75 µm) as a cementitious component.

 

Figure 1-1 Recycled glass mountains which hardly find their ways into remelting facilities,

Wyoming [7]

 

Figure 1-2 Stockpile of waste glass, Huntington, West Virginia, USA [8]

While the first approach (sand replacement) seems to be easier and more practical due to the challenges and difficulties in grinding glass into fine powder, the second approach (use of glass powder as a cementitious material) can provide superior benefits, including:

• Reducing embodied energy and CO₂ emissions associated with concrete through replacement of energy and CO₂ intensive Portland cement.
• Providing potential economic profits: It is known that portland cement is the most expensive constituent of concrete and its replacement with a low-cost recycled material can be economically profitable.
• Improving concrete durability due to pozzolanic reaction of glass powder: It is known that glass powder can provide pozzolanic properties which can reduce mass transport inside concrete and improve its durability.
• Providing a widely available supplementary cementitious material (SCM) with consistent composition and properties: Unlike other SCMs such as fly ash and slag with widely variable compositions and properties, soda-lime glass shows much more consistent composition and properties. While local availability of fly ash and slag depends on vicinity to local power plants and steel mills, glass is widely available in all population centers.

Whether used as aggregate or cement replacement, glass is not just filling the space, but undergoes chemical reactions inside concrete. This is specifically due to the dissolution of glass structure in the high pH of concrete pore solution and subsequent reactions with available elements (e.g., Ca, Na, or Al). The final results could be a deleterious alkali silica reaction (ASR) or a positive and beneficial pozzolanic reaction (PR). It is observed that the size of glass particles determines whether ASR or PR is expected to be dominant: ASR is the prevalent reaction for glass particles larger than approximately 0.3 mm [11] , while pozzolanic reaction (PR) is more common when finely ground glass powder, usually smaller than 75 µm, is used in concrete (Figure 1-3).The detailed discussions and reasons for such a dual, size dependable behavior of glass are discussed in the published papers by the author [11-13] (Appendix C) which is also reviewed in chapter 2.

Sand replacement:

• ASR is dominant
• Concrete

cracking/expansion may occur

• ASR mitigation methods must be employed

Cement replacement: • Pozzolanic reaction is dominant

• Safe concrete, no cracking
• Increases concrete durability
• May reduce concrete’s early age strength

 

Figure 1-3 Crushed glass can be used as sand or cement (the focus of this study) replacement in concrete

The main objective of this research is to study and promote the performance of glass powder as a cementitious material in concrete using alkaline solutions. In the next sections, both pozzolanic reaction of glass powder and alkali silica reaction (ASR) of larger glass cullet are briefly introduced.

1.3. Pozzolanic reaction (PR) of glass powder

Pozzolanic powders (e.g., coal fly ash, silica fume, blast furnace slag, rice husk ash, glass powder, etc.) are primarily composed of amorphous or poorly crystalline siliceous components, which enable them to be used as partial (usually less than 50%) replacement of portland cement (PC). Pozzolanic reaction is the consequence of the interactions between silica or silicate ions, calcium (usually from Ca(OH)₂) and aqueous solutions, which results in formation of calciumsilicate-hydrate (C-S-H). Calcium hydroxide (CH) can be provided through hydration of PC (as a by-product) or be directly mixed with these powders and aqueous solution.

S  +  CH  +  H  à  C-S-H                 (Eq.1-1)

 

The letters C, S, and H are shorthand notations used in cement chemistry literature for referring to lime (CaO), silica (SiO₂) and water (H₂O), respectively. Other shorthand notation of common cement oxides include A: Alumina (Al₂O₃), F: Ferrite (Fe₂O₃), ͞S: SO_3, N: Na₂O, K: K₂O, ͞C=CO₂[9] .

C-S-H or (CaO)x(SiO₂)(H₂O)_y – which is the main cementitious component in concrete- does not have an exact stoichiometry; x depends on the local availability of CaO and SiO₂at the time of C-S-H formation (commonly x is 1.0 to 1.7) [14] . The water content (y) depends, among other factors, on ambient conditions: as concrete dries, C-S-H loses water. C-S-H is the main hydration product of portland cement (C₃S or C₂S):

C₃S or C₂S + Hà CH  + C-S-H              (Eq. 1-2)

When glass powder is used in concrete as PC replacement (where it is known as a supplementary cementitious material, SCM), pozzolanic reaction begins with dissolution of silicate glass (or the glassy phase of a pozzolanic material) in concrete pore solution which is an alkaline fluid. The source of alkalinity is usually from the alkali sulfates (Na₂SO₄, K₂SO₄) contained on the surface of portland cement particles. Also, the abundance of soluble Ca(OH)₂ ensures that pH of concrete pore solution remains above ≈12.4. Figure 1-4 shows the hydration products of portland cement and the pozzolanic reaction of glass powder.

 

Figure 1-4 Hydration products of Portland cement and pozzolanic reaction of glass powder in concrete

As seen in Figure 1-4, two types of calcium-silicate-hydrate (C-S-H) form in concrete: one from portland cement hydration (named C-S-H_(h) on the figure) and the other from pozzolanic reaction (C-S-H_(p)); both providing binding properties. Figure 1-5 is a SEM image, showing the two types of C-S-H materials in a polished section of a PC mortar containing glass powder. C-SH from Portland cement hydration can form a rim surrounding cement particles or it can dissolve and precipitate away from the cement particles (known as ground mass C-S-H). The kinetics of

portland cement hydration are faster than that of SCMs and as a result, C-S-H_(h) forms much faster than C-S-H_(p). The Ca/Si ratio in C-S-H_(h) is usually more than that of C-S-H_(p) . Therefore, when glass powder (or other pozzolans) is replaced by portland cement, the early-age strength of concrete may decrease.

 

Figure 1-5 C-S-H phases formed by Portland cement hydration and pozzolanic reaction of a glass particle when used as a SCM

 

Figure 1-6 shows the results of the relative compressive strength of concretes containing various contents of glass powder (smaller than 41 µm). Comparable and even higher strength is achieved only at later ages (more than 200 days) when glass powder was used. Therefore, the main challenge in replacing portland cement with glass powder is the slow rate of pozzolanic reaction, which restricts many applications for such concrete mixtures. Not all construction jobs can wait for 200 days before concrete gains proper strength. One approach to accelerate the pozzolanic reaction of glass powder is further grinding of the powder to smaller sizes. However, this practice can be challenging and cost/energy inefficient. Another approach which is examined in this research is the use of alkaline solutions (also known as alkali activators) to enhance the pozzolanic reaction of glass powder by accelerating its dissolution rate.

 

Figure 1-6 Reduction in early strength of concrete by replacement of 10-40 % Portland cement with glass powder [15] . After about 200 days, the strength of concrete containing glass powder reaches the strength of the control (100% PC) concrete

 

It should be noted here that some of the introduced pozzolanic materials (specifically fly ash and slag) contain significant amounts of calcium and aluminum in addition to silica, which (in addition to their pozzolanic performance) enables them to be used as the sole binding component in production of portland cement free concrete. For example, fly ash (rich in Al and Si) can be mixed with alkaline solutions (NaOH or sodium silicate) and form sodium-aluminum-silicatehydrate (N-A-S-H) products (also known as geopolymer), which provide strong binding properties. Formation of cementitious products from the sole utilization of slag and fly ash is not the scope of this study and the reader is referred to [16-18] .

1.4. Alkali silica reaction (ASR) of glass cullet

ASR is a type of slow and deleterious reaction that occurs between reactive siliceous aggregates such as flint, chert, and recycled glass cullet and concrete’s alkaline pore solution. The product of such reaction is an amorphous silica gel, known as ASR gel. This gel is hygroscopic and expands by water absorption, thus applying stress to its surrounding concrete, which eventually leads to concrete expansion and cracking. As mentioned before, when glass particles larger than 0.3 mm are used in concrete, ASR is prevalent [11-13] . Previous studies by the author showed that unlike pozzolanic reaction which occurs at the surface of glass particles, ASR occurs merely inside intra-particle cracks of glass [11, 12] .Figure 1-7shows a SEM image of a large glass particle inside concrete which has undergone ASR. It should be noted that the surface of large glass particles still undergoes pozzolanic reaction, but since a large surface area is required for the pozzolanic reaction to show its effectiveness, the pozzolanic reaction of glass powder is much more pronounced. It has been shown that ASR in glass aggregate is directly related to existence of intra-particle cracks, which originate during bottle crushing [11-12] . Small particles contain tighter cracks and significantly lower crack densities. As such, ASR in small glass particles (usually smaller than 0.3 mm) is limited or non-existent. The use of thermally annealed glass particles (to remove micro-cracks), or utilization of crack-free glass beads did not result in formation of ASR gel and mortar expansion [12, 19] .

Figure 1-7 A glass particle (1.2 to 2.4 mm) which has undergone ASR from within, leading to cracking of the paste

 

1.5. Research objectives

Although incorporation of GP in concrete has been tested in the past, no systematic attempt was made to understand the involved mechanisms of the interactions between GP and concrete environment (i.e., pore solution) to promote its relatively slow cementitious properties. The hypothesis of this research is that by using alkaline solutions, it is possible to improve and accelerate the cementitious performance of glass powder in concrete. However, there are some knowledge gaps that need to be filled to increase our understanding of GP performance in concrete to properly evaluate this hypothesis. The objectives of this research are to address the following questions:

1. What are the main physical and chemical interactions involved between soda-lime glass and highly concentrated alkaline solutions?
2. Is it possible to accelerate the rate of the reaction between glass powder and calcium hydroxide by using alkaline solutions? If so, to what extent?
3. What is the overall performance of concrete when alkaline solutions are used to accelerate the cementitious performance of GP?
4. What are the micro-scale properties of the cementitious components that form through pozzolanic reaction of GP in concrete, in comparison to conventional cementitious materials?

To answer these four objectives, this study presents a step-by-step approach through multiple tasks described in the following section. Such an approach and resulting information is currently non-existent even for conventional SCMs such as slag, and fly ash. Thus, the results have broader impacts in improving the performance of all SCMs other than glass powder in concrete. This work also leads to significant sustainability benefits by diverting a waste material from landfills and by reducing the embodied energy and carbon footprint of concrete by replacing portland cement. In addition, this research can improve the understanding of alkali silica reaction (ASR) and its mitigation techniques, which will be applicable to other natural reactive aggregates. These allow an ideal optimization of the concrete proportions and the choice of chemical and physical treatments that result in the best possible performance.

 

 

1.6. Tasks and organization of the contents

This research is composed of 4 tasks (as summarized in Table 1-1 and in accordance with the four research objectives described above) to increase our knowledge of the performance of GP in concrete. These tasks are separately studied in chapters 3 to 6.

Table 1-1 Specific tasks of this research to address the four objectives described in section 1.5.

Task		Desired outcomes
Task 1: Analysis of the kinetics of silicate glass interactions with highly concentrated alkaline solutions and  characterization of soda-lime glass dissolution products	     	Measurement of kinetic parameters of glass dissolution Assessment of the role of calcium in solution Measurement of concentration of Si and Ca in solution Evaluation of the morphology and composition of the solid dissolution products by SEM/EDS Analysis of the mineralogy of the product by XRD  Comparison of the mineralogy and microstructure of the solid products in wet vs. dry state
		Analysis of the interface between glass and dissolution solid products using TEM
Task 2: Analysis of the reaction between GP and Ca(OH)2	  	Measurement of the effect of NaOH solution on the rate of GP and Ca(OH)2 reaction Measurement of the stoichiometry of the reaction between GP and Ca(OH)2 Investigation of the characteristics of the reaction products using SEM/EDS and XRD methods
Task 3: Performance of mortars containing alkali activated GP	 	Effectiveness of alkali activation on strength development in 4 types of mortars: CH-GP, PC-GP, Slag-GP and fly ash-GP ASR susceptibility of alkali activated slag and fly ash mortars with GP
		Microstructural evolution of alkali activated slag and fly ash mortars containing GP
Task 4: Analysis of micro-scale mechanical properties of cementitious products of GP	 	Feasibility of using peak-force tapping AFM to measure micro-scale modulus of pozzolanic reaction products of soda-lime glass Comparison  of the results with binding phases of PC and alkali activated slag and fly ash

Chapter 2 provides a background literature review of previous research on the use of recycled glass in concrete. A summary of the authors’ past research (during his MSc studies) on the use of recycled glass cullet as sand replacement in concrete is also provided. Chapter 3 presents the methods and results of a study aiming to address research objective #1. At first, the kinetic parameters of silicate glass dissolution (specifically soda-lime type) in highly concentrated alkaline solutions are studied and quantified. This is conducted using a static glass dissolution experiment. The rate of glass mass loss as well as the evolution of Si and Ca concentration in NaOH solutions is monitored. Specific attention was made on the role of calcium presence in the solution on the rate of glass dissolution. This is important as calcium is usually available in concrete pore solution due to the presence of Ca(OH)₂ solids. After that, using characterization techniques the morphology and mineralogy of the solid dissolution products of soda-lime glass in alkaline solutions are evaluated in detail. Furthermore, focused ion beam (FIB) was employed to prepare thin sections for TEM analysis for studying the interface between glass and corrosion products.

Chapter four provides the results and findings towards objective #2. Pastes of GP- Ca(OH)₂ were made with either 1M NaOH or water to investigate the effect of alkali activation on accelerating the rate of the reaction between glass powder and CH. Quantification was made through accurate measurements of GP and Ca(OH)₂ content/consumption of the pastes using TGA and selective acid dissolution methods. Furthermore, the composition and mineralogy of the pozzolanic reaction products of glass with CH was conducted using XRD and SEM/EDS techniques, focusing on the role alkali activation.

 Chapter five addresses objective #3 where GP is incorporated in four binary mortar systems including: 1) GP-CH; 2) GP-portland cement; 3) GP-slag; and 4) GP-fly ash.

Compressive strength, susceptibility to ASR expansion and microstructural development of some of the selected systems are discussed.

Towards addressing objective #4, chapter six presents some preliminary results of the analysis of micro-scale mechanical properties of various cementitious phases using peak force tapping AFM. These include the pozzolanic reaction product of soda-lime glass in PC system, binder phases formed through hydration of portland cement, alkali activated of slag and fly ash systems. Finally, chapter seven provides a summary of the findings and conclusions of this study. Areas for future research are identified and introduced to improve the knowledge on application of glass powder in concrete.

Chapter 4 of this research is a published journal paper: (Maraghechi H., Maraghechi M., Rajabipour F., Pantano C.G., (2014) “Pozzolanic reactivity of   recycled glass powder at elevated temperatures: Reaction stoichiometry, reaction products and effect of alkali activation”, Cement and Concrete Composite 53, 105-114.)

Chapter 5 has been submitted to the journal of Cement and Concrete Composite as a research paper, and Chapter 3 and 6 will be submitted to the journal of Cement and Concrete Research as separate research papers.

 

1.7. References

• Ashby M. (2009), Materials and the Environment, Elsevier, Burlington, MA.
• Damtoft J.S., Lukasik J., Herfort D., Sorrentino D., Gartner E.M. (2008), Sustainable development and climate change initiatives, Cement and Concrete Research, 38, 115-127.
• Environmental Protection Agency (EPA), (2013), Municipal Solid Waste Generation, Recycling, and Disposal in the United States: Facts and Figures for 2012 (www.epa.gov).
• Rajabipour F., Fischer G., Sigurdardottir P., Goodnight S., Leake A., and Smith E. (2009), Recycling and Utilizing Waste Glass as Concrete Aggregate, TRB Annual Conference, CD-Rom Paper # 09-2195, Transportation Research Board, Washington, DC.
• Available on: <http://www.epa.gov/wastes/conserve/materials/glass.htm>, Retrieved on April.

• PCA Handbook, Design and Control of Concrete Mixtures, (2008), Portland Cement Association, 14th Edition.
• Gruver M., In Cheyenne, glass pile shows recycling challenges (2009), Associated Press, Available: < http://www.komonews.com/news/business/62338547.html >, Retrieved on April 2014.
• Amos J.L. (1993), Available: <http://www.corbisimages.com/stock-photo/rightsmanaged/JA004525/bucket-loader-at-green-glassstockpile/?tab=details&caller=search>, Retrieved on April 2014.
• Mindess S., Young J.F., Darwin D. (2003), Concrete, 2nd Ed., Prentice Hall, Upper Saddle River, New Jersey.

10. McLeod R.S., (2011), Ordinary Portland cement, with extraordinarily high CO2 emissions, Available on: <http://www.uaecement.com/articles/ordinary_portland_cement.pdf> ,  Retrieved on April 2014.
11. Rajabipour F., Maraghechi H., Fischer G. (2010), Investigating the Alkali Silica Reaction of Recycled Glass Aggregates in Concrete Materials, ASCE Journal of Materials, 22 (12) 1201-1208.
12. Maraghechi H., Shafaatian S.H.M., Fischer G. and Rajabipour F. (2012), The Role of Residual Cracks on Alkali Silica Reactivity of Recycled Glass Aggregates, Cement and Concrete Composites, 34,(1), 41-47.
13. Shafaatian S.M.H., Akhavan A. Maraghechi H., Rajabipour F. (2013), Study of the Mechanisms of ASR Mitigation by Fly Ash in ASTM C1567 Mortars Containing Recycled Glass Aggregates, (2011), Cement and Concrete Research, 37, 143–153.
14. Taylor H.F.W. (2004), Cement Chemistry, 2nd Edition Thomas Telford Publishing.
15. Idir R., Cyr M., Tagnit-Hamou A. (2011), Pozzolanic properties of fine and coarse color-mixed glass cullet, Cement and Concrete Composites 33(1), 19-29.
16. Bernal S.A., Provis J.L. (2014), Durability of Alkali-Activated Materials: Progress and Perspectives, Journal of the American Ceramic Society, 97- 4, 997–1008.
17. Luo X., Xu J., Bai E., Li W. (2012), Systematic study on the basic characteristics of alkaliactivated slag-fly ash cementitious material system, Construction and Building Materials, 29, 482486.
18. Shi C., Roy D., Krivenko P., (2006), Alkali Activated Cements and Concretes, Taylor and Francis.
19. Rajabipour F, Maraghechi H, Shafaatian S.M.H. (2012), ASR and its mitigation in mortars containing recycled Soda-Lime glass aggregates, 14th International Conference on Concrete Alkali Aggregate Reactions (ICAAR), Austin, Texas.

DEVELOPMENT AND ASSESSMENT OF ALKALI ACTIVATED RECYCLED GLASS-BASED CONCRETES FOR CIVIL INFRASTRUCTURE

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