th 9 Austroads Bridge Conference, Sydney, New South Wales 2014 IMPORTANCE OF REACTIVE SIO 2 , AL 2 O 3 AND NA2 O IN GEOPOLYMER FORMATION Chandani Tennakoon, Swinburne University of Technology, Australia Ahmad Shayan, ARRB Group, Australia Kwesi Sagoe-Crentsil, CSIRO, Australia Jay G Sanjayan, Swinburne University of Technology, Australia ABSTRACT Geopolymer is an alternative for Portland cement based binder. It has shown better or similar engineering and durability properties compared to Portland cement based binders. The properties of geopolymer depend on the characteristics of the aluminosilicate source material used. Hence, it is important to identify the characteristics of the source material that results in a binder with good mechanical properties. This paper investigates the levels of reactive (amorphous) SiO 2 and Al 2 O 3 contents of source materials and alkali oxides content of Si-rich geopolymer binders required to achieve enhanced mechanical properties. The study also evaluates the roles of Na 2 O and particle size in the development of geopolymer micro-structures. We have used six different Australian Class F fly ashes as aluminosilicate source materials in geopolymer binders. These materials were characterised using XRF, XRD and particle size analyser in order to determine the bulk chemical composition, mineralogy (including content of amorphous phases) and particle size distribution. Geopolymer pastes were subsequently prepared by activating the selected fly ashes with liquid alkaline activators and the samples where cured at 60 ᴼC for 24 hrs. A constant flow was maintained for all mixtures, the contributions of Na 2 O, SiO 2 and H 2 O content from the alkaline activator are different for each fly ash source. The compressive strength results showed that high strengths are given for mixtures in which the molar ratio of reactive constituents lie within the ranges SiO 2 /Al 2 O 3 < 5 and Na 2 O/ reactive (SiO 2 + Al 2 O 3 ) 0.09-0.12. INTRODUCTION Geopolymer binders are produced reacting aluminosilicate source materials with highly alkaline liquids. The term “geopolymer” was first introduced by Joseph Davidovits. The reaction creates three dimensional Si-O-Al-O bonds form monomers resulting in a poly (sialates) structure which contains SiO 4 and AlO 4 tetrahedral interconnect by sharing oxygen atoms. Furthermore, cations + + +2 (Na ,K ,Ca ) are required to balance the negative charge due to coordination of aluminium or any broken bonds in the framework structure (Xu, 2002). The reaction mechanism of geopolymerisation involves a series of dissolution and precipitation/condensation reactions (Davidovits, 2008). © ARRB Group Ltd and Authors 2014 1 th 9 Austroads Bridge Conference, Sydney, New South Wales 2014 1. Dissolution of SiO 2 and Al 2 O 3 sources: -1 Al 2 O 3 + 3H 2 O + 2OH → 2Al(OH) 4 → SiO(OH) 3 → SiO 2 (OH) 2 SiO 2 + H 2 O + OH SiO 2 + 2OH -1 -1 -1 -1 2- 2. Condensation of silicate and aluminate species: 2-1 -1 + Na + SiO 2 (OH) 2 or SiO(OH) 3 + Al(OH) 4 →Na 2 O-Al 2 O 3 -SiO 2 -H 2 O gel A number of factors control the chemistry of the above process. They are the amorphous content of oxides (SiO 2 , Al 2 O 3 , CaO), physical properties (particle size and shape) alkali activator content of the synthesis, mixing procedures and curing regime. The properties of geopolymer binders, however, depend on the aluminosilicate material properties, alkaline solution chemistry, mixing and curing regime (Duxson et al., 2007b, Khale and Chaudhary, 2007, Bakharev, 2005, Chancey, 2008, Bakri et al., 2011). Fly ash, slag, red mud and rice husk ash or geological resources like metakaoline and kaolin are used as aluminosilicate source materials in geopolymer. Chemical and physical properties of these materials vary widely because of source origin or geological history, thermal process, etc. These properties include SiO 2 , Al 2 O 3 and SiO 2 /Al 2 O 3 , ratio, particle size, amorphous content and calcium content in the raw material. It is difficult to change alumino silicate material characteristics significantly particularly in by-products like fly ash. Hence, the properties of the final geopolymer binder are unpredictable. Previous research has been carried out to discover a correlation between geopolymer and aluminosilicate material properties. Duxson and Provis (2008) correlated on the basis of total aluminium content, silica content and network modifier cations of source materials to the strength of respective binder systems in a ternary diagram. They designed this ternary diagram using bulk chemical compositions of the alumino silica source materials and blast furnace slag. They concluded that alumino silica sources with less network modifier (i.e. Ca, Mg) content tend to produce low strength geopolymer binders. However, it was apparent that certain aluminasilicate source materials did not necessarily conform to the proposed trend. While the study showed broad trends it did not reveal any clear boundary demarcating inter-relationships between bulk chemical compositions of alumino-silicate source materials. For fully amorphous and reactive metakaolin feedstock material, De Silva et al. (2007) reported characteristic higher strength for systems with SiO 2 /Al 2 O 3 molar ratio in the range of 3.4 - 3.8. Parallel studies by Duxson et al. (2007a) also disclosed that maximum strength results were achievable for similar ratios in metakaolin systems. More recently, Autef et al. (2012) demonstrated that the geopolymerisation reaction rate increases with the decline of quartz SiO 2 in the system. Despite the finding, they observed complete participation of amorphous silica in the reaction to fully develop the geopolymer network. In addition, they found the optimal SiO 2 /Al 2 O 3 ratios for metakaolin based geopolymer in the region of 3 and 3.6. Duxson and Provis (2008) categorized the source materials in a ternary diagram according to the total aluminium content, silica content and network modifier 2+ 2+ cations (Ca , Mg etc.) with the strength of the binder. There was no clear boundary between strength ranges in there diagram corresponded to chemical composition. Van Jaarsveld et al. (2003) observed that high amorphous content fly ashes result in better mechanical properties in binders whereas Brouwers and Van Eijk (2002) confirmed the dissolution rate of SiO 2 and Al 2 O 3 in the aluminosilicate material to be proportional to glass content of the fly ash. Pietersen et al. (1989) researched fly ash reactivity during cement hydration and reported that the ratio between network forming oxides (SiO 2 + Al 2 O 3 + Fe 2 O 3 ) and network modifier oxides (Na 2 O + K 2 O + CaO + MgO) in the glass structure of fly ash range should be between 4 and 9 to obtain better reactivity. © ARRB Group Ltd and Authors 2014 2 th 9 Austroads Bridge Conference, Sydney, New South Wales 2014 This paper discusses the best selection criteria of aluminosilicate source material to get high compressive strength. In addition, contributions from alkaline oxides, particle size, water content and reactive oxide components towards compressive strength development are evaluated. EXPERIMENT PROCEDURE Materials Six types of Class F fly ashes obtained from six different Australian power stations; Gladstone, Collie, Mt Piper, Eraring, Tarong and Bayswater were used as the main alumina-silica source materials in this study. D-Grade sodium silicate solution (29.4 SiO 2 and 14.7 % Na 2 O by weight) from PQ Australia and analytical grade NaOH solid from Sigma Aldrich were used as alkaline activators. Characterisation of fly ashes The overall chemistry and mineralogy of fly ashes were analysed by XRD and XRF techniques. Particle size of the materials was obtained using a Cilas laser diffraction particle analyser. The chemical compositions of the fly ashes are given in Table 1 while Table 2 shows the mineralogical phases percentage of fly ashes. Using the formula of the mineral, the amount of crystalline Al 2 O 3 and SiO 2 present in the mineral phases can be calculated. By subtracting this value from the total values given in chemical composition, the amorphous content or reactive components of Al 2 O 3 and SiO 2 present in each fly ash can be obtained. Figure 1 shows the particle size distribution variation for Australian Class F fly ashes and Table 3 summarises particle size distribution in percentage values. Table 1: Bulk chemical composition of fly ashes SiO 2 Al 2 O 3 CaO MgO Fe 2 O 3 Na 2 O P2O5 Cr 2 O 3 K2O5 MnO SO 3 LOI TiO 2 Total Gladstone 51.11 25.56 4.3 1.45 12.48 0.77 0.885 0.7 0.15 0.24 0.57 1.32 99.62 Collie 60.02 24.61 0.15 0.99 8.56 0.36 0.217 0.04 0.36 0.04 0.18 1.49 1.53 99.43 Mt Piper 65.77 26.72 0.05 0.25 1.32 0.32 0.139 2.69 0.02 0.11 1.44 1.11 100.28 Eraring 63.18 25.22 0.07 0.57 3.36 0.72 0.251 1.81 0.07 0.18 1.31 0.99 100.26 Tarong 73.05 23.22 0.07 0.14 0.89 0.06 0.046 0.52 0.02 0.06 0.75 1.31 100.36 Bayswater 80.43 14.02 0.04 0.31 3.57 0.1 0.087 0.85 0.04 0.08 0.54 0.49 100.36 Table 2: Mineralogical phases of fly ashes Gladstone Collie Mt Piper Eraring Tarong Bayswater Quartz Mullite 12.95 14.57 8.42 7.76 5.58 9.15 8.12 13.08 5.88 7.11 8.75 8.56 Hematite Magnetite 4.17 1.88 1.87 1.71 1.88 - - - 2.21 6.52 80.22 8158 78.78 87.01 73.94 Amorphous 66.38 © ARRB Group Ltd and Authors 2014 3 th 9 Austroads Bridge Conference, Sydney, New South Wales 2014 Figure 1: Particle size distribution of Class F fly ashes Table 3: Particle size distribution (passing percentage) Gladstone Collie Mt Piper Eraring Tarong Bayswater 90%(µm) 24.44 43.33 41.83 55.85 40.09 35.25 50%(µm) 5.54 11.58 12.94 18.21 12.34 12.76 10%(µm) 1.1 1.61 2.23 3.02 2.71 2.54 Mean(µm) 9.32 17.38 17.96 24.64 17.25 16.22 Preparation of geopolymer samples All geopolymer paste mixes were prepared by mixing each fly ash with alkaline activators. In preparing the mixtures, solid NaOH was first dissolved in water to obtain 8M sodium hydroxide solution. The solution was cooled to room temperature before mixing with the fly ash. Sodium hydroxide and sodium silicate solution (1:1 ratio) were added to fly ash in the required amounts in order to achieve equal flow for mixtures. The ratio between two alkaline activators is kept as unity. The alkali activated mixtures were cast in 50 mm cubes that were sealed to prevent o moisture loss. The cubes were subsequently cured at 60 C and 100% RH for 24 hrs, after which samples were removed from the moulds and placed in sealed polythene bags for storage till testing. Table 4 shows geopolymer mix formulations for different fly ashes. Mix7, Mix8 and Mix9 were obtained by blending 50% Gladstone and 50% Tarong, 50% Gladstone and 50% Bayswater, 30% Gladstone and 70% Tarong fly ashes respectively. Important oxide ratios are tabulated in Table 5 and calculations for the ratios are described as follows: • Reactive SiO 2 = SiO 2 from fly ash amorphous phases + SiO 2 from sodium silicate activator • Reactive Al 2 O 3 = Al 2 O 3 from fly ash amorphous phases • Reactive SiO 2 /Al 2 O 3 of source material = SiO 2 from fly ash amorphous phases/Al 2 O 3 from fly ash amorphous phases • Total Reactive SiO 2 / Al 2 O 3 = Reactive SiO 2 /Al 2 O 3 © ARRB Group Ltd and Authors 2014 4 th 9 Austroads Bridge Conference, Sydney, New South Wales 2014 Table 4: Class F fly ash geopolymer binder mix designs for equal flow Mix no Mix formulation Fly ash(g) NaOH+ Na 2 SiO 3 (g) Mix1 Mix2 Mix3 Mix4 Mix5 Mix6 Mix 7 Mix 8 Mix 9 Gladstone Collie Mt Piper Eraring Tarong Bayswater 50%Gladstone/50%Tarong 50%Gladstone/50%Bayswater 30%Gladstone/70%Tarong 3000 3000 3000 3000 3000 3000 3000 3000 3000 800 1200 1300 1650 1900 1850 1272 1200 1440 Liquid/ Solid mass ratio 0.267 0.400 0.433 0.550 0.630 0.617 0.424 0.400 0.480 Table 5: Important oxide ratios and 28 day compressive strength Mix no Mix1 Mix2 Mix3 Mix4 Mix5 Mix6 Mix7 Mix8 Mix9 Total reactive SiO₂/Al₂O₃ Molar ratio 3.7 4.6 5.0 5.7 6.6 14.8 5.1 7.4 5.7 Reactive SiO₂/Al₂O₃ Molar ratio of fly ash 3.28 4.13 4.53 4.87 5.78 13.1 4.60 6.65 5.10 Water to total solid mass ratio 0.16 0.23 0.24 0.30 0.33 0.34 0.24 0.23 0.27 28 days Na 2 O/(reactive average SiO 2 +Al 2 O 3 ) compressive molar ratio strength (MPa) 0.098 48 0.102 37 0.097 18 0.136 15 0.123 21 0.129 20 0.110 35 0.106 37 0.112 32 RESULTS AND DISCUSSION According to the particle size distributions (Figure 1 and Table 3), Gladstone fly ash has the smallest particle size compared to the other Australian fly ashes. Other fly ash types also have 90% of particles less than 55 µm. Diaz and Allouche (2010) investigated 25 different Class F and class C fly ash, according to their conclusion when fly ash has very small particles(<90µm) has high strength ( higher than 50 MPa). Geopolymertic leaching occurs (Si and Al ion leaching) on the surface of the fly ash particle, therefore it is important to have fine particles and a large surface area (Diaz and Allouche, 2010, Palomo et al., 1999). Figure 2 shows the compressive strength variation for the geopolymer pastes. Gladstone and Collie fly ashes based geopolymers(Mix1 and Mix2) showed one day strength 40 and 20 MPa respectively. On the other hand, Tarong and Bayswater fly ash based geopolymer (Mix5 and Mix6) had very poor compressive strength performance (5 and 6 MPa respectively). Nevertheless, blending Gladstone fly ash with Tarong and Bayswater increased the strength values (Mix7, Mix8, and Mix9). This is discussed thoroughly in the next paragraph. © ARRB Group Ltd and Authors 2014 5 th 9 Austroads Bridge Conference, Sydney, New South Wales 2014 Figure 2: Compressive strength variation of Class F fly ash based geopolymer pastes Figure 3 shows the compressive strength variation Gladstone and Tarong blended geopolymers. 100% Gladstone fly ash based geopolymer (Mix1) has 48 MPa in 28 days. Moreover, 100% Tarong fly ash based geopolymer has 21 MPa (Mix5). When Gladstone fly ash is blended with Tarong geopolymer, the strength value is higher (> 30 MPa). Possible reasons could be the initial 100% Tarong and Bayswater fly ash based synthesis had high SiO 2 contents and consumed high alkaline liquid to get consistent workability. It may be noted that those geopolymer systems have higher water content and higher Na 2 O content. However, Gladstone fly ash appears to adjust the chemistry of the Tarong and Bayswater fly ashes thereby improving mix workability. Fletcher et al. (2005) concluded that aluminosilicate systems with high silica, consume higher water content than other systems. Figure 3: Average 28 days compressive strength variation in Tarong and Gladstone blended geopolymer systems Figure 4 illustrates the compressive strength variation with total reactive SiO 2 /Al 2 O 3 ratio. Mix1 and Mix2 geopolymers have reactive SiO 2 /Al 2 O 3 ratio in between 3.5 and 4.6 and achieved a compressive strength value over 30 MPa in 28 days. Mix3 to Mix6 geopolymer had a higher reactive SiO 2 /Al 2 O 3 (> 5) and lower 28 days compressive strength value (< 25 MPa). Mix7 to © ARRB Group Ltd and Authors 2014 6 th 9 Austroads Bridge Conference, Sydney, New South Wales 2014 Mix9 geopolymer pastes do not follow the same co-relationship between reactive SiO 2 /Al 2 O 3 and compressive strength as other mixtures. However, the final reaction product (Na 2 O-Al 2 O 3 -SiO 2 -H 2 O gel) may evolve concurrently either into a crystalline zeolitic phase or to an amorphous geopolymer phase depending on the concentration of available aluminate and silicate species in solution. The formation of zeolitic phases is a common feature in geopolymer systems and the type of zeolite formed usually depend on the SiO 2 /Al 2 O 3 ratio of the system (De Silva and Sagoe-Crentsil, 2008, Oh et al., 2011, Hajimohammadi et al., 2010, Buchwald et al., 2011, Kovalchuk et al., 2008). Na 2 OAl 2 O 3 -SiO 2 -H 2 O gel compositions with higher or lower than SiO 2 /Al 2 O 3 ≈ 4 usually develop into zeolitic phases (De Silva and Sagoe-Crentsil, 2008). This possibly accounts for the presence of Si rich zeolitic phases such as faujasite. Zeolitic crystalline phases in alkali activated binders are unstable than 3 dimensional geopolymer network. Fletcher et al. (2005) analysed for metakaoline based geopolymer systems with different SiO 2 /Al 2 O 3 ratios ranging from 0.5 to 300. They found that when SiO 2 /Al 2 O 3 ratio is greater than 24 geopolymer binder becomes more rubbery than brittle behaviour. Moreover, geopolymer binder with lower SiO 2 /Al 2 O 3 (< 2) ratio or high aluminium content shows weak structure with several discrete compounds. Chindaprasirt P et al. (2012) reported that most favourable SiO 2 /Al 2 O 3 ratio for mechanical properties of the geopolymer in the range of 3.2 - 3.7. They observed that when the SiO 2 /Al 2 O 3 ratio is increased more than 4, high calcium fly ash based geopolymer systems, the mechanical properties decrease. De Silva et al. (2007) reported that metakaoline based geopolymer systems with the SiO 2 /Al 2 O 3 ratio in the range of 3.4 - 3.8 showed the highest strength. . This is in line with Thakur and Ghosh (2009). Fernández-Jiménez et al. (2006) stated that fly ashes with the highest reactive SiO 2 /Al 2 O 3 ratio (4.76) exhibit the lowest mechanical strength (below 25 MPa within 7 days) compared to other ash types with lower SiO 2 /Al 2 O 3 ratios. However, they did not take reactive SiO 2 /Al 2 O 3 molar ratios into account. Figure 4: Average 28 days compressive strength variation with total reactive SiO 2 /Al 2 O 3 ratio for geopolymer Figure 5 illustrates the average 28 days compressive strength variation with water to total solid ratio. Mix3 has a significantly low level of water to solid ratio (0.24) in the geopolymer system but the strength value is lower than 20 MPa. Panias et al. (2007) showed that when water content in the geopolymer mixture decreases compressive strength increases exponentially. It is obvious that, excessive water in the geopolymer evaporates creating voids in the binder. It can affect the mechanical properties of the binder (Diaz and Allouche, 2010). Diaz and Allouche (2010) provide evidence to prove that high alkaline liquid weakens the geopolymer binders. In their work, some geopolymer binders with lower liquid to fly ash ratio (0.4) had lower compressive strength (< 45 MPa). But some geopolymers with a higher liquid to fly ash ratio © ARRB Group Ltd and Authors 2014 7 th 9 Austroads Bridge Conference, Sydney, New South Wales 2014 (0.66) had a higher compressive strength (> 45 MPa). There is no direct co-relationship with water content in the binder and the geopolymer compressive strength. Figure 5: Average 28 days compressive strength variation with water to total solid mass ratio Figure 6 shows the variation in 28 days compressive strength with the molar ratio of available Na 2 O to reactive (SiO 2 + Al 2 O 3 ) in the geopolymer systems. Dissolution of SiO 2 and Al 2 O 3 is mainly based on amorphous content and as well as alkalinity of the system. As seen in Figure 6, geopolymer systems with different mix designs are correlated well with the alkalinity as well as total reactive alumina silica components (amorphous SiO 2 and Al 2 O 3 ). Chen-Tan et al. (2009) observed that amorphous content of the alumina-silicate material decreases quickly and crystalline phase dissolves comparatively slowly in the alkaline liquid. This results are in line with those of (Fernández-Jiménez and Palomo, 2003). Álvarez-Ayuso et al. (2008) stated that higher amorphous content led to geopolymer binder becoming more stable and strong. If high content of mullite or quartz are present in the fly ash, the reactivity of Al-Si bearing fraction decreases drastically (Álvarez-Ayuso et al., 2008). Even though Mix1 and Mix3 have the almost equal alkalinity to amorphous (SiO 2 + Al 2 O 3 ) molar ratio (i.e. 0.98), the strength value is different significantly 48 MPa and 18 MPa. Mix3 has higher reactive SiO 2 /Al 2 O 3 ratio compared to Mix1. The strength value depend on the reactive SiO 2 /Al 2 O 3 ratio and the Na 2 O/(SiO 2 +Al 2 O 3 ). Na 2 O controls the fly ash dissolution process. Therefore it is important to have appropriate alkaline environment in geopolymer synthesis. Pietersen et al. (1989) explained that fly ash digestion starts with ion exchange and finally bulk glass phase dissolution. Moreover, fly ash with high alkaline increased the pH of the pore solution and thereby improved the reactivity. Van Jaarsveld and Van Deventer (1999) concluded that alkalinity of the geopolymer influences in every stage of the geopolymer even after setting. In Figure 2, Mix5 and Mix6 showed better compressive strength (> 20 MPa) in 28 days while their 7 day compressive strength was very low (< 10 MPa). High alkaline content in pore solution particularly in Mix5 and Mix6 geopolymer can participate for further dissolution process of unreacted fly ash. Further investigations need for clarification. © ARRB Group Ltd and Authors 2014 8 th 9 Austroads Bridge Conference, Sydney, New South Wales 2014 Figure 6: Average 28 days compressive strength variation with Na 2 O/ (reactive SiO 2 +Al 2 O 3 ) molar ratio There is a combination effect for the geopolymer reaction from factors: SiO 2 and Al 2 O 3 , particle size distribution, liquid to solid ratio and alkalinity of the system. However, considering the above results obtained most critical factors for strong geopolymer network are the reactive SiO 2 /Al 2 O 3 and Na 2 O/reactive (SiO 2 +Al 2 O 3 ). CONCLUSIONS Based on the outcome of this work the following conclusions can be drawn. • Aluminosilicate material with high reactive SiO 2 / Al 2 O 3 molar ratio (>5) tends to absorb high alkaline liquid contents. • Blending Gladstone fly ash with other fly ashes significantly increase the compressive strength of the resulting geopolymer. • The most suitable Na 2 O to reactive (SiO 2 + Al 2 O 3 ) molar ratio is in the range between 0.09-0.12. • The combination of the molar ratios ranges of reactive SiO 2 /Al 2 O 3 < 5 and Na 2 O/ reactive (SiO 2 + Al 2 O 3 ) 0.09-0.12 gives higher compressive strength values. ACKNOWLEDGEMENT The research was supported by Austroads project (TS1835) awarded to the ARRB Group,. Authors would also like to acknowledge Bill Sioulas from Fly Ash Australia for providing fly ash samples. REFERENCES Álvarez-Ayuso, E., Querol, X., Plana, F., Alastuey, A., Moreno, N., Izquierdo, M., Font, O., Moreno, T., Diez, S., Vázquez, E. & Barra, M. 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Journal of Materials Science, 42, 729-746. Kovalchuk, G., Fernández-Jiménez, A. & Palomo, A. (2008), Alkali-activated fly ash. Relationship between mechanical strength gains and initial ash chemistry. Materiales de construccion, 58, 35-52. Oh, J. E., Moon, J., Mancio, M., Clark, S. M. & Monteiro, P. J. M. (2011), Bulk modulus of basic sodalite, Na 8 [AlSiO 4 ] 6 (OH) 2 ·2H 2 O, a possible zeolitic precursor in coal-fly-ash-based geopolymers. Cement and Concrete Research, 41, 107-112. © ARRB Group Ltd and Authors 2014 10 th 9 Austroads Bridge Conference, Sydney, New South Wales 2014 Palomo, A., Grutzeck, M. W. & Blanco, M. T. (1999), Alkali-activated fly ashes: A cement for the future. Cement and Concrete Research, 29, 1323-1329. Panias, D., Giannopoulou, I. P. & Perraki, T. (2007), Effect of synthesis parameters on the mechanical properties of fly ash-based geopolymers. Colloids and Surfaces A: Physicochemical and Engineering Aspects, 301, 246-254. Pietersen, H. S., Fraay, A. L. A. & Bijen, J. M. (1989), Reactivity of fly ash. Fly ash and coal coversion by-products VI, 178, 139 -157. Thakur, R. N. & Ghosh, S. (2009), Effect of mix composition on compressive strength and microstructure of fly ash based geopolymer composites. Journal of Engineering and Applied Sciences, 4, 68-74. Van Jaarsveld, J. G. S. & Van Deventer, J. S. J. (1999), Effect of the alkali metal activator on the properties of fly ash-based geopolymers. Industrial & Engineering Chemistry Research, 38, 3932-3941. Van Jaarsveld, J. G. S., Van Deventer, J. S. J. & Lukey, G. C. (2003), The characterisation of source materials in fly ash-based geopolymers. Materials Letters, 57, 1272-1280. Xu, H. (2002), Geopolymerisation of aluminasilicate minerals.PhD, The University of Melbourne. AUTHOR BIOGRAPHIES Chandani Tennakoon is currently pursuing A Ph.D. degree at the Faculty of Science, Engineering and Technology, Swinburne University of Technology. She is working in collaboration with the ARRB Group Melbourne, Australia to investigate the durability of fly ash based geopolymer concrete for bridge constructions. Her current research interests include geopolymer binders, sustainable construction materials and durability of geopolymer concrete. Dr Ahmad Shayan is a Chief Research Scientist at ARRB. He was Chairman, Standards Australia Committee CE/12 for 10 years, served on IOC of many AAR conferences, and was Chairman, 10th IAARC, Melbourne, 1996. His research interests include AAR, DEF, waste materials utilization in concrete, steam cured concrete, corrosion of steel reinforcement in concrete, utilization of stainless steel in concrete under aggressive environments and use of CFRP to confine AAR-induced expansion of concrete elements. He has written over 400 papers and technical reports. He won the prestigious Clunies Ross Medal in 2003 for his work on durability of concrete structures. Professor Kwesi Sagoe-Crentsil received his PhD in 1987 from the University of British Columbia, Vancouver, Canada and joined CSIRO in 1993. His career at CSIRO has focused on technology development roles including leading multi-disciplinary teams in the development of sustainable materials and process technologies. His contributions to the emerging field of geopolymer technology have focused on the implications of varying oxide ratios and the fundamental mechanisms governing silicate dissolution and condensation reactions. Professor Jay G Sanjayan is the Director of the Centre of Sustainable Infrastructure at Swinburne University of Technology. He joined Swinburne in 2010 following a 22 year academic career at Monash University. He is the Chairman of the editorial board of the Concrete in Australia journal, associate editor of materials and structures journal and editorial board member of the journal of sustainable cement-based materials. His main research interests are geopolymer concrete, fire resistance of concrete, and development of alternative cements for geo-sequestration of carbon dioxide. © ARRB Group Ltd and Authors 2014 11 th 9 Austroads Bridge Conference, Sydney, New South Wales 2014 Copyright Licence Agreement th The Author allows ARRB Group Ltd to publish the work/s submitted for the 9 Austroads Bridge Conference, granting ARRB the non-exclusive right to: • publish the work in printed format • publish the work in electronic format • publish the work online. The Author retains the right to use their work, illustrations (line art, photographs, figures, plates) and research data in their own future works The Author warrants that they are entitled to deal with the Intellectual Property Rights in the works submitted, including clearing all third party intellectual property rights and obtaining formal permission from their respective institutions or employers before submission, where necessary. © ARRB Group Ltd and Authors 2014 12
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