Sulfate soil stabilisation with silica fume-based binders
Sulfate soils are encountered in nearly every country in the world. These soils, where calcium-based stabilisers are added, can undergo heave-induced expansion as a result of the formation of ettringite. Therefore, this research examines the viability of using silica fume (a by-product of silicon industry) as a partial replacement of different high/low/non-calcium-based binders to restrict the ettringite formation and suppress the expansion associated thereof. To do so, this study relied on the use of laboratory experiments using two types of soil (artificial sulfate kaolinite soil-KG and natural high sulfate soil-Gypsum Marl (GM) Clay, three hydraulic binders (Lime-L,Cement-C and Magnesium oxide-M), two supplementary materials (GGBS-GS and Silica fume-S) and one sulfate (Gypsum-G) type. The result revealed that the strength and expansion performance was proportional to gypsum (G) and lime (L) concentrations, of which a G/L ratio of 1.5 yielded the highest magnitude, thus it was categorised as the worst-case scenario. In addition, the binary blended (5M-5S) and ternary blended (3M-3.5GS-3.5S) stabilisers exhibited superior performance, as they demonstrated resistance to expansion as low as 0.2-0.3% and yielded relatively higher robustness against water immersion (<20% strength reduction) in the presence of worst sulfate case scenario. The application of these innovative binders is anticipated to alleviate the socio-economic and environmental concerns associated with calcium-based stabilisers in the presence of sulfate and promote a more sustainable sulfate soil stabilisation technique.
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