Investigation Into the Effect of Admixed Cement and Rice Husk Ash on Hydraulic Conductivity, Shrinkage and Strength Properties of Black Cotton Soil

Abstract

Black cotton soil (BCS) is problematic for liner construction due to its high plasticity, swelling potential, and permeability. This study investigates the stabilization of BCS using cement and rice husk ash (RHA) to enhance its engineering properties for use as a compacted clay liner in waste containment and water retention structures. BCS samples were stabilized with cement at 1%, 2%, and 3% combined with RHA at 2%, 4%, and 6%. The treated soils were subjected to standard compaction, unconfined compressive strength (UCS), volumetric shrinkage and hydraulic conductivity. The results indicate that stabilization significantly improved the geotechnical properties of BCS. The optimum mix of 3% cement + 6% RHA lowered the optimum moisture content from 19.2% to 14.5% and increased the maximum dry density from 1.61 to 1.86 Mg/m³, indicating improved compaction characteristics. UCS at 28 days increased from 148 kN/m² to 365 kN/m², satisfying the minimum strength requirement for liner materials. Hydraulic conductivity decreased by 92%, from 2.97 × 10⁻⁶ to 2.23 × 10⁻⁷ cm/s, meeting the permeability criteria for low-to-moderate hazard liners. The findings demonstrate that 3% cement + 6% RHA stabilization effectively refines the pore structure and enhances the strength and impermeability of BCS, making it viable for liner applications. This approach also provides an environmentally sustainable method for utilizing RHA while reducing cement consumption.