APPLICATION OF MICROBIALLY INDUCED CALCITE PRECIPITATION TO IMPROVE POORLY GRADED SANDY SOIL

The challenges associated with improving or strengthening poor soil consistently necessitated investigation to establish a novel, environmentally acceptable, and sustainable soil improvement method. The MICP (microbially induced carbonate precipitation) approach is one method in which microorganism metabolic pathways are used to create calcite precipitation inside the soil matrix, improving soil engineering qualities. This study aims to examine the efficiency of the MICP approach in improving the California Bearing Ratio value and reduction in permeability of poorly graded sand. Aerobic bacteria, namely Bacillus Subtilis, was used in this investigation for ureolysis and calcite precipitation. Three distinct concentrations of urea-calcium chloride solution (50, 300, and 600 mmol/L) treatment conditions were explored in the experimental program, and the California Bearing Ratio (CBR) value and permeability of the soil was determined for the targeted soil. This investigation indicated that the MICP has caused a significant quantity of calcite precipitation, resulting in a substantial improvement in the strength and a reduced permeability of the poorly graded sandy soil. Scanning electron microscopy (SEM) examination testing of the produced CaCO3 crystals indicated that the CaCO3 predominantly created connections from point to point between the particles of sand throughout the process of precipitation.