Justification of strength properties of microstructural changes in the black cotton soil stabilized with rice husk ash and carbide lime in the presence of sodium salts

Abstract

Black cotton soils exhibit high shrinkage and swelling characteristics due to the variation in moisture content. To overcome this problem, many techniques are adopted, among which is the soil stabilization technique. Rapid industrialization and urbanization lead to the generation of waste products; the major by-products are rice husk ash (RHA) and carbide lime (CL). These by-products show excellent pozzolanic property. In this paper, an attempt has been made to stabilize black cotton soil with rice husk ash (RHA) along with carbide lime (CL) and other additives. Based on strength test results, the optimum dosage of RHA and CL was found to be 20% and 8%, respectively. The effect of sodium salts on index properties and unconfined compression strength (UCC) test at different moulding water contents for immediate testing and at different days of curing are studied. Results show that plasticity index of the soil treated with additives was decreased both for immediate and for 7 days of curing period due to the decrease in diffuse double-layer thickness. Soil–RHA–CL composite treated with 1% sodium chloride and 1% sodium hydroxide improves the Unconfined compression strength and shows a better strength compared to carbide lime-treated soil due to the formation of alkali silicate and alkali aluminate hydrated gel along with other cementitious products. The microstructural changes in the stabilized composite can be observed with XRD and SEM analysis. The addition of carbide lime and salts binds the particle with hydrated gel and shows denser environment compared to unstabilized soil.