Stabilisation of Black Cotton Soil Using Red Mud: An Alumina Extraction Byproduct

This study investigates the stability of Black Cotton (BC) soil which is known for its high shrinkage and compressibility difficulties in civil engineering by reinforcing it with Red Mud (RM), an industrial waste by-product from the Bayer aluminium process, and lime [Ca (OH) ]. To address the issues of weak BC soil and industrial waste disposal, the BC soil sample was mixed with RM in increments ranging from 10% to 50%, and the effect of adding 4% lime was also investigated. The index and engineering characteristics of these stabilised soil combinations were tested during lengthy curing periods (0, 7, 14, 30, 60, 90, 180, and 365 days), filling a large gap in the literature about the long-term impacts of curing on expansive soils. Scanning Electron Microscope (SEM) examination was performed on the improved combinations to better understand the microstructural alterations that contribute to strength increases. The findings show, that the addition of 30% RM and 4% optimum lime greatly enhanced the engineering qualities of BC soil over time and the strength of the combination enhanced from 40.07 kN/m2 to 116.31 kN/m2 for immediate testing. Following a 365-day curing period, the UCS rose from 116.31 kN/m2 to 615.49 kN/m2, demonstrating the effectiveness of this stabilising method for engineering applications. As to the microstructural analysis, adding lime to a mixture of BCS and RM promotes a gradual densification process over time. 30% RM and 4% lime stabilisation efficiently transform the original loose, porous structure into a consolidated matrix with enhanced mechanical properties. Major Findings: The study demonstrated that incorporating RM along with lime significantly enhanced the geotechnical properties of BC soil. An extended curing period of up to 365 days improved soil strength and reduced expansiveness. SEM analysis highlighted microstructural transformations that played a major role in the stabilisation process.