Effect of Bacterial Calcium Carbonate Precipitation with Rice Husk Ash on Compressive Strength of Silty Sand

A relatively green and sustainable method of soil improvement known as “biocementation” or “microbial-induced calcite precipitation” (MICP) has appeared recently. It involves the production of calcium carbonate (CaCO3) crystals utilizing bacteria and cementation solution (CS) between soil particles in order to enhance the soil’s properties. The objective of the current study is to assess the effect of biocementation process with and without Rice Husk Ash (RHA) on compressive strength of silty sand. RHA is an agricultural waste that exhibits good pozzolanic properties due to its high concentration of silica. The laboratory tests were conducted with different combinations of bacterial solution (BS) concentration (0.5, 1.0, and 1.5 optical density (OD)) and cementation reagent concentration (0.5, 1.0, and 1.5 Molarity (M)) at 0, 3, 7, 14, and 28 days’ curing. Again all the tests were repeated with the addition of 5, 10, and 15% RHA to compare the results. The compressive strength of the soil was increased when biocementation process, with and without RHA, was applied. The highest increment in compressive strength at 1.0OD and 0.5 M with 10% RHA after 14-day curing time was found to be 206.38 kN/m2. The chronological sequence in terms of strength performance was observed as: biocemented soil mixed with RHA > biocemented soil > RHA mixed-soil > untreated soil. In concluding remarks, biocementation process (with and without RHA) was found to be an effective technique for improving compressive strength of silty sand, and mixing of RHA to the biocemented soil enhanced the effectiveness of biocementation in the enhancement of compressive strength.