Investigation of the Recycling of Geopolymer Cement Wastes as Fine Aggregates in Mortar Mixes
Abstract:Fly ash-slag based Geopolymer Cement (GPC) is presenting mechanical properties and environmental advantages that make it the predominant “green” alternative to Portland Cement (PC). Although numerous life-cycle analyses praising its environmental advantages, disposal after the end of its life remains as an issue that has been barely explored. The present study is investigating the recyclability of fly ash-slag GPC as aggregate in mortars. The purpose of the study was to evaluate the effect of GPC fine Recycled Aggregates (RA), at replacement levels of 25% and 50%, on the main mechanical properties of PC and GPC mortar mixes. The results were compared with those obtained by corresponding mixes incorporating natural and PC-RA. The main physical properties of GPC-RA were examined and proven to be comparable to those of PC-RA and slightly inferior to those of natural sand. A negligible effect was observed at 28-day compressive and flexural strength of PC mortars with GPC aggregates having a milder effect than PC. As far as GPC mortars are concerned, the influence of GPC aggregates was enhancing for the investigated mechanical properties. Additionally, a screening test showed that recycled geopolymer aggregates are not prone of inducing alkali silica reaction.
 A. Hasanbeigi, L. Price and E. Lin, “Emerging Energy-efficiency and CO2 Emission-reduction Technologies for Cement and Concrete,” 2013
 M. C. Forde, ICE Manual of Construction Materials, London: Thomas Telford Limited, 2009.
 J. Kline and C. Kline, “"Cement and CO2: What is Happening.,” IEEE Transactions on Industry Applications, 2015.
 E. Gartner, “Industrially interesting approaches to "low-CO2" cements,” vol. 34, no. 9, 2004.
 J. Davidovits, “Environmental implications of Geopolymers,” Elsevier, 29 June 2015. (Online). Available: http://bit.ly/21Z1byQ. (Accessed 15 January 2016).
 J. Davidovits, “Geopolymer Cement: A Review,” Institute Geopolymere, France, Saint-Quentin, 2013.
 G. Habert, G. d'Espinose, J. de Lacaillerie and N. Roussel, “An environmental evaluation of geopolymer based concrete production: reviewing current research trends,” Journal of Cleaner Production, vol. 19, no. 11, 2011.
 M. Fawer, M. Concannon and W. Rieber, “Life cycle inventories for the production of sodium silicates,” The International Journal of Life Cycle Assessment, vol. 4, no. 4, 1999.
 A. Heath, K. Paine and M. McManus, “Minimising the global warming potential of clay based geopolymers,” Journal of Cleaner Production, vol. 78, 2014.
 T. C. Hansen, “Recycled aggregates and recycled aggregate concrete second state-of-the-art report developments 1945-1985,” Materials and Structures, vol. 19, no. 3, 1986.
 R. K. Dhir, M. C. Limbachiya and T. Leelawat, “Suitability of recycled concrete for use in BS 5328 designated mixes,” Proc. Instn Civ. Engrs Structs & Bldgs, pp. 257 - 274, Augoust 1999.
 H. K. Wai, R. Mahyuddin, J. K. Kenn and Z. S. Mohd, “Influence of the amount of recycled coarse aggregate in concrete design,” Construction and Building Materials, vol. 26, p. 565–573, 2012.
 R. Silva, J. de Brito and R. Dhir, “The influence of the use of recycled aggregates on the compressive strength of concrete: a review,” European Journal of Environmental and Civil Engineering, p. DOI 10.1080/19648189.2014.974831, 2014a.
 K. N. J., S. M. Akash Rao, “Use of aggregates from recycled construction and demolition waste in concrete,” Resources, Conservation and Recycling 50, p. 71–81, 2007.
 L. L. Lenke and J. Malvar, “Alkali Silica Reaction Criteria for Accelerated Mortar Bar Tests Based on Field Performance Data,” Lexington, KY, USA, 2009.
 D. L. Gress, R. L. Kozikowski and T. T. Eighmy, “Accelerated ASR testing of recycled concrete,” Waste Materials in Construction, pp. 221-233, 2000.
 J. Gerardu and C. Hendricks, “Recycling of road pavement materials in Netherlands,” 1985.
 Z. Zhao, S. Remond, D. Damidot and W. Xu, “Influence of fine recycled concrete aggregates on the properties of mortars,” Construction and Building Materials 81, p. 179–186, 2015.
 L. Evangelista and J. de Brito, “Mechanical behaviour of concrete made with fine recycled concrete aggregates,” Cement & Concrete Composites 29, p. 397–401, 2007.
 P. Goncalves and J. de Brito, “Recycled aggregate concrete (RAC) comparative analysis of existing specifications,” Magazine of Concrete Research 62, No. 5, doi: 10.1680/macr.2008.62.5.339, p. 339–346, May 2010.
 K. Paine and R. Dhir, “Recyccled aggregates in concrete: A performance-related approach,” Magazine of Concrete Research 62, No7, pp. 519-530, July 2010.
 M. C. Limbachiya, T. Leelawat and R. K. Dhir, “Use of recycled concrete aggregate in high-strength concrete,” Materials and Structures Vol. 33, pp. 574-580, 2000.
 X. Shi, F. Collins, X. Zhao and Q. Wang, “Mechanical properties and microstructure analysis of fly ash geopolymeric recycled concrete,” Journal of Hazardous Materials 237– 238, p. 20– 29, 2012.
 R. Silva, J. de Brito and R.K. Dhir, “Properties and composition of recycled aggregates from construction and demolition waste suitable for concrete production,” Construction and Building Materials 65, pp. 201-217, 2014b.
 P. Duxson, A. Fernandez-Jimenez, J. L. Provis, G. C. Lukey, A. Palomo and J. S. J. van Deventer, “Geopolymer technology: the current state of the art,” J Mater Sci, DOI 10.1007/s10853-006-0637-z, p. 2917–2933, 2007.
 B. Rangan, “Engineering properties of geopolymer concrete,” in Geopolymers-Structure, Processing, Properties and Industrial Applications, D. provis, Ed., Woodhead, 2009, pp. 221-226.
 S. Mandal, R. C. Chavda, S. N. Birmole and H. K. Shah, “Geopolymer,” Popular plastics & Packaging, pp. 38-42, November 2014.
 X.-S. Shi, Q.-Y. Wang, X.-L. Zhao and F. G. Collins, “Structural behaviour of geopolymeric recycled concrete filled steel tubular columns under axial loading,” Construction and Building Materials 81, p. 187–197, 2015.
 L. Zhang, “Complete Recycling and Utilisation of Waste Conrete Through Geopolymerization,” C&D World, pp. 30-34, May/June 2012.