Two-Phase Stabilization of Black Cotton Soil in Kenya Using Sodium Chloride and Cement

Abstract

This study explores the two-phase stabilization of Black Cotton Soil (BCS) in Kenya using sodium chloride and Portland cement to enhance strength and reduce swelling. A staged cement addition method—comprising primary and secondary dosages—was applied to improve soil structure and dimensional stability. Laboratory evaluations, including linear shrinkage, liquid limit, free swell, and Unconfined Compressive Strength (UCS), were conducted on specimens with cement additions of 50–150 kg/m³. Results indicate that the two-stage process significantly decreased shrinkage and increased UCS, particularly at higher cement levels. The method also proved environmentally safe, with hexavalent chromium levels below regulatory limits based on TCLP 1311 leaching tests. The findings demonstrate that staged cement addition provides a sustainable and cost-effective solution for stabilizing expansive soils. This study then aims to evaluate the effectiveness of a two-phase cement stabilization process using sodium chloride in improving the physical and mechanical properties of Black Cotton Soil in Kenya, and providing insights into sustainable utilization of expansive soils in construction.