Investigation of various gram-positive bacteria for MICP in Narmada Sand, India

In lieu of the conventional carbon-intensive and expensive cement-based ground improvement methods, microbially induced calcite precipitation (MICP) method has gained prominence recently as a sustainable approach to improve the engineering properties of soil. MICP involves calcification by microbial processes, inducing cementation effect in granular soil particles. Several studies have demonstrated the use of Sporosarcina pasteurii bacteria to improve density, stiffness, shear strength, and liquefaction resistance of sand. However, the effects of different bacteria on calcite formation have not been systematically examined in the Indian context. This study investigates MICP in poorly graded, liquefiable Narmada sand, using gram-positive bacteria (i.e. Sporosarcina pasteurii, Bacillus subtilis, and Bacillussphaericus). Several controlled microbial and cementation media concentrations were tested in sand-filled tubes. Calcite precipitation was analyzed using SEM, FTIR, XRD, and calcimeter. Bacillus subtilis and Bacillus sphaericus resulted in calcite precipitation comparable to that of Sporosarcina pasteurii and can be utilized for sand stabilization.