Effective Utilization of Coal Gangue for Stabilizing Black Cotton Soil: Geotechnical Performance and Microstructural Insights

Coal gangue (CG) is a waste generated during coal mining, accounting for 10-25% of the coal extracted. Black cotton soil (BCS) detrimentally affects superstructures due to its volume changes and hence is a persisting challenge. To suppress this, there is an utmost need to enhance the strength of BCS. In this study, the synergetic effects of CG and lime as stabilizers for BCS are examined. The experimental investigation includes evaluating critical geotechnical properties of BCS, specifically unconfined compressive strength (UCS) and durability to understand the extent of blended stabilization. The experimental design incorporates CG dosages of 10%, 20%, and 30% of the dry weight of BCS along with lime dosages of 4%, 6%, and 8%. Findings reveal a notable improvement in the UCS and durability of BCS when incorporating 20% CG with 6% lime. Also, the California bearing ratio (CBR) test was performed on the optimum mixture for applicability as subgrade and subbase material. Mineralogical and microstructural analysis, carried out using X-ray diffraction (XRD) and Scanning electron microscope (SEM), respectively, substantiates the strength enhancement is due to the formation of cementitious compounds. Thus demonstrating the potential of CG blended lime as an effective solution for soil stabilisation. This study offers a promising avenue for construction in challenging geotechnical environments.