Conference Dates

May 27-June 1, 2018


Uncalcined geopolymer-stabilised soils have shown potential for replacing concrete and fired clay as low carbon masonry materials. There is now a good fundamental understanding of how aluminosilicate precursors react to form geopolymer phases in simple systems, but there is a knowledge gap for the more complex systems of real soils where minor phases may influence behaviour. Because the clay minerals and their proportions differ between soils, as well as minor phases present, we are still not able to easily predict which soils are suitable for geopolymer stabilisation. In this study, a comparison was made for the alkali activation of real and ‘fake’ soils. Three soils from around the world (UK, India, Sudan) of known mineralogical composition were used. From the real soils’ known mineralogical compositions, ‘artificial soils’ corresponding to each one were made. These were made by mixing refined clays in the same proportions, and using quartz sand as a substitute for all other non-clay phases. The soils were mixed with sodium hydroxide activator and cured. The phases formed were characterised using XRD, FTIR and SEM. From the elemental compositions, the most significant difference was the quantities of iron and calcium present in minor phases. The phases and proportions formed by the alkali activation of each real soil broadly match those formed by the fake soils. The implication for the development of geopolymer-stabilised soil materials is that for a fixed activating solution, minor phases have limited influence on the geopolymer reaction. Nevertheless, the complexity of reaction with mixed soils makes it difficult to predict reaction phases and therefore final products.

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