Comparison of Gypsum and MICP in Stabilizing an Expansive Soil

ABSTRACT Expansive soils are considered problematic for civil engineering applications due to their low strength, high compressibility, and poor bearing capacity, which limit their use as foundation or pavement subgrade materials. To overcome these limitations, this study investigates the stabilization of expansive soil using gypsum and Microbially Induced Calcite Precipitation (MICP) as strengthening agents. The experimental program was carried out in three stages. In the first stage, gypsum, an industrial by-product, was incorporated into the soil in varying proportions of 2%, 4%, 6%, 8%, and 10% by dry weight. The treated samples were tested for Unconfined Compressive Strength (UCS) and California Bearing Ratio (CBR). The results revealed a significant improvement in strength with increasing gypsum content up to 4%, beyond which a slight reduction was observed. Thus, 4% gypsum was identified as the optimum content for stabilization. In the second stage, MICP treatment was applied by introducing bacterial solutions in concentrations of 2 ml, 4 ml, 6 ml, 8 ml, and 10 ml under optimum moisture conditions. The treated samples were tested for Unconfined Compressive Strength (UCS) an