Mechanical Performance of Black Cotton Soil Stabilized with Bagasse Ash Incorporating Limestone Calcined Clay Cement Under Varied Loading Conditions

Construction of geotechnical infrastructures in tropical regions characterized by black cotton soil (BCS) presents major engineering challenges due to its high swelling and shrinkage potential. Bagasse ash (BA) incorporating limestone calcined clay cement (LC3) has emerged as a promising stabilization approach to enhance the performance of foundations constructed on BCS. In this study, BCS specimens were stabilized using a BA-LC3 binder at proportions ranging from 0% to 18% by dry mass of soil and cured for 7-28 days at temperatures of 10°C and 32°C to evaluate their mechanical response under loading conditions. Consolidated drained direct shear and triaxial tests were conducted under varying confining pressures to assess the mechanical performance of the treated BCS. The results show that the peak shear strength of treated BCS increased with increasing confining pressure, curing period and curing temperature. Shear strength increased by 76.2% on average, considering 450-kPa confining pressure, 28-day curing period and 32°C curing temperature. An optimal BA-LC3 binder content for BCS was found to obtain the highest internal friction angle, which ranged around 15% content at 28 curing days and 32°C curing temperature. Failure behavior also varied significantly between untreated and treated soils. Untreated BCS exhibited ductile behavior, whereas BA-LC3 stabilized BCS presented brittle behavior. The findings demonstrate the feasibility of using BA-LC3 binder system to improve the shear behaviour of BCS for geotechnical applications in tropical regions. This approach supports sustainable construction practices by reducing cement consumption, lowering carbon emissions and decreasing infrastructure development costs.