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Concrete In Australia : March 2012
Concrete in Australia Vol 38 No 1 55 contributor to emissions; contributing 76.4% of CO2-e for OPC concrete. However, the alkali activators expend significant energy during manufacture and the contribution of the geopolymer binder (fly ash + sodium silicate + sodium hydroxide) is 201 kg CO2-e/m3 compared with OPC 269 kg CO2-e/m3 (25.2%). (ii) Elevated temperature curing of geopolymer concrete is not considered in 13,15-17 whereas this is a key source of emissions (39.976 kg CO2-e/m3 or 12.4% of the total emissions). (iii) e sourcing/mining/treatment/transport of raw materials for manufacture of sodium hydroxide and sodium silicate were not considered by 15, 16. In this study, audited records of energy expenditure by Australian sodium silicate manufacturers were unavailable for analysis and therefore our calculations are based on Fawer 18. It is recommended that future studies include this data. A further consideration would be to compare geopolymer concrete with CO2-e arising from blended fly ash or slag cements that comprise partial replacement of OPC. Although we have not conducted contrasting calculations on specific blended cement concrete mixtures, 13-22% reductions in CO2-e are feasible 6 and would provide lower CO2-e than geopolymer binders. 7.0 CONCLUSIONS is study quantified the carbon dioxide equivalent emissions (CO2-e) generated by all the activities necessary to obtain raw materials, concrete manufacturing and construction of one cubic metre of concrete, non-reinforced and strength of 40 MPa, on a construction site in metropolitan Melbourne. is study compared the CO2-e footprint generated by concretes comprising geopolymer binders and 100% OPC concrete. e findings of the study were unexpected. e CO2 footprint of geopolymer concrete was approximately 9% less than comparable concrete containing 100% OPC binder, much less than predictions by other studies. e key factors that led to the higher than expected emissions for geopolymer concrete were the energy expenditure associated with: (i) mining, treatment and transport of raw materials for manufacture of alkali activators; (ii) expenditure of significant energy during manufacture of alkali activators; and (iii) the need for elevated temperature curing of geopolymer concrete to achieve reasonable strength. Furthermore and beyond the scope of this study, other environmental aspects need consideration. In particular, ozone depletion, photochemical ozone creation, and acidification were reported by Stengel 14 to be more favourable in the case of OPC concrete. ACKNOWLEDGEMENT e authors wish to thank the Department of Civil Engineering at Monash University for supporting this research. REFERENCES 1. Gartner, E., "Industrially interesting approaches to low- CO2 cements", Cement and Concrete Research, 34(9), 2004, pp1489-1498. 2. Winnefeld F, Leemann A, Lucuk M, Svoboda P, Neuroth M. "Assessment of phase formation in alkali activated low and high calcium fly ashes in building materials", Construction and Building Materials 24, 2010, pp 1086- 93. 3. Humphreys, K. & Mahasenan, M. 2002. Towards a Sustainable Cement Industry -- Substudy 8: Climate Change. World Business Council for Sustainable Development. Switzerland. 4. Meyer, C., " e greening of the concrete industry", Cement and Concrete Composites, 31(8), 2009, pp 601- 605. 5. Huntzinger,D.N. & Eatmon,T.D. "A life-cycle assessment of cement manufacturing: comparing traditional process with alternative technologies", J. Cleaner Production, 17(7), 2009, pp 668--675. 6. Flower, D. J. M. & Sanjayan, J. G., "Green House Gas Emissions due to Concrete Manufacture", Int J LCA 12 (5), 2007, pp. 282-288. 7. Davidovits, J. (1991) Geopolymers: Inorganic Polymeric New Materials. Journal of thermal analysis 37, 1633- 1656. 8. Duxson, P., Fernandez-Jimenez, A., Provis, J. L., Lukey, G. C., Palomo, A. & van Deventer, J. S. J. "Geopolymer technology: the current state of the art", J. Materials Science, 42, 2007, pp 2917-2933. 9. Palomo A, Grutzeck MW, Blanco MT. "Alkali-Activated Fly Ashes, A Cement for the Future", Cement and Concrete Research, 29(8), 1999, pp 1323-1329. 10. Barbosa, V.F.F. and MacKenzie, K.J.D. " ermal behaviour of inorganic geopolymers and composites derived from sodium polysialate", Materials Research Bulletin, 38, 2003, pp. 319--331. 11. Xu, H. and Van Deventer, J.S.J. " e geopolymerisation of alumino-silicate minerals", International Journal of Mineral Processing, 59, 2000, pp. 247--266. 12. Hardjito, D., Wallah, S. E., Sumajouw, D. M. J. & Rangan, B. V. "Fly ash-based geopolymer concrete", Australian Journal of Structural Engineering, 6 (1), 2005, pp 77-84. 13. van Deventer JSJ, Provis JL, Duxson P, Brice DG. Chemical Research and Climate Change as Drivers in the Commercial Adoption of Alkali Activated Materials, Waste Biomass Valor, 1, 2010, pp 145-155 14. Stengel, T., Reger, J. & Heinz, D. "LCA of geopolymer concrete -- What is the environmental benefit?", Proceedings Concrete 09, 24th Biennial Conference of the Australian Concrete Institute 2009 Sydney 15. Witherspoon, R., Wang, H., Aravinthan, T. & Omar, T. "Energy and Emission Analysis of Fly Ash Based Geopolymers", Proceedings SSEE International Conference -- Solutions for a Sustainable Planet, 2009 Melbourne. Society for Sustainability & Environmental Engineering. 16. Habert, G., D espinose de LaCaillerie, J. B., Lanta, E.