Bio-Stabilization of Mahanadi Sand: An RSM-Optimized MICP Approach

This study investigates the enhancement of Mahanadi river sand using Microbial Induced Calcite Precipitation (MICP) optimized through Response Surface Methodology (RSM). The effects of varying bacterial concentrations (10³ to 108 CFU/ml), cementation solution concentrations (0.25 M to 2 M), pH (5–9), temperature (10 °C–50 °C), and curing duration (7, 14, 28 days) were systematically analyzed for improvements in California Bearing Ratio (CBR) and permeability. A total of 42 CBR and 78 permeability tests were performed, and the optimal condition was found at 108 CFU/ml bacterial solution with 2 M cementation solution, achieving a maximum CBR of 20.89% after 28 days over three times the untreated value and a 75% reduction in permeability (from 3.8 mm/min to 0.96 mm/min) after 14 days. Temperature around 30-35°C and pH of 7-7.5 yielded the highest calcite precipitation. SEM and XRD analysis confirmed enhanced interparticle bonding due to CaCO3crystallization and precipitated calcite as dominant mineral phase contributing major strength gain.. The RSM-based models demonstrated high predictive accuracy with R2 values of 93.08% for CBR and 94.74% for permeability, validated through lack-of-fit and ANOVA analysis.