Study on Effect of Microbial Induced Calcite Precipitates on Strength of Soil

The challenges to strengthen the weak soil always prompted the need for further research investigation to develop a new, eco-friendly and sustainable method of soil stabilization. One possible technique is Microbial-Induced Calcite Precipitation (MICP) which has recently emerged as a sustainable technique for soil improvement. This study focuses on bacterial calcium carbonate precipitation and its effect on the compressibility and strength of soil. Two different types of soils (high plastic clay and low plastic clay) were used for the study. A species of Bacillus group B.megaterium (MTCC-428) was used to activate and catalyze the calcite precipitation caused by reaction between urea and calcium chloride. MICP uses bacteria to hydrolyses urea and give carbonate ions which react with a calcium chloride solution to produce calcium carbonate (calcite) that binds the soil particles together leading to increased soil strength and stiffness. Nutrient delivery system was use to induce cementation reagents. Variable parameters such as concentration of cementation reagent (0.25M, 0.50M, 0.75M, 1M) and curing period (1day, 3day, 7day) were studied. These parameters were applied on both the type of soils in specified duration and range to utilize the effect of MICP. From the results there were perceived improvement (1.15-2 times) in unconfined compressive strength in both the type of soils. It was also found that the strength increased with increment in treatment duration.