Influence of Cementing Solution Concentration on Calcite Precipitation Pattern in Biocementation

Abstract

Enhancing the strength characteristics of soil by mechanical, chemical, biological or a combination of these approaches needs thorough investigation. One of the most sustainable biological methods to improve the engineering property of soil is Microbial-Induced Calcite Precipitation (MICP). MICP is the process in which the urease-producing bacteria in the presence of cementing solution deposits calcite in the soil voids thereby enhancing the in situ soil shear strength mainly by binding the particles together. For efficient bio-cementation, not only the amount of calcium carbonate but also its precipitation pattern is one of the major influencing factors. Earlier studies have depicted the pattern of calcium carbonate deposition for soil saturated with bacteria and cementing solution; however, the gap exists to understand the efficiency in relation to the percolated flow of bacteria and cementing solution. Keeping this in view, the current study is focused on understanding the precipitation pattern of calcium carbonate induced by Sporosarcina pasteurii (NCIM 2477) and cementing solution. This is achieved by sand column experiment with percolation method under different concentrations of cementing solution in unsaturated soil conditions and SEM-EDAX image analysis of the specimen derived from sand columns. Our results suggest that the concentration of cementing solution affects the precipitation pattern. We conclude that the sand columns percolated with S pasteurii cells followed by addition of multiple doses of low concentration of cementing solutions at defined time intervals resulted in the homogeneous pattern of calcite precipitation.