Enhancing Soil Strength at Targeted Calcite Content via Optimizing Chemical Application Parameters Using Taguchi Method for Biocementation

Abstract

Soil strength improvement employing microbial induced calcite precipitation (MICP) involves bio-geo-chemical interaction among bacteria (here, Sporosarcina pasteurii), sand, and cementing solution. A critical review of literature opened the gap in exploring the strength gain for a given amount of CaCO3 precipitation, investigating the influence of chemical concentration and its application methodology. Thereby, the current study aims to independently maximize the calcite precipitation efficiency and unconfined compressive strength while targeting the calcite deposition of 10%–12%. In the present study, the Taguchi method of experimental design followed by analysis of variance and analysis of mean was adopted to optimize the outcome parameters. Results depicted the extreme variation in obtained strength in a small range of calcite deposition. Further, the microscopic investigation employing micrographs and elemental mapping reveals a higher impact of CaCO3 depositional characteristics than its amount on strength gain. The current study envisages the importance of chemical application parameters to improve efficiency and economy while reducing soil contamination due to non-reacting chemicals.