Applicability of Soybean Crude Urease-Calcite Precipitation (SCU-CP) Method for Improvement of Expansive Soil

Abstract

Expansive soil is one of the problematic soils that can swell and shrink, causing damage to buildings. Expansive soil needs improvement before being used for buildings. The typical method for expansive soil improvement is mixing soil with additives such as cement, lime, and fly ash. However, mixing additives like cement, lime, and fly ash is not easy to distribute evenly and negatively impacts the environment. Soybean Crude Urease-Calcite Precipitation (SCU-CP) is a soil improvement method currently being developed. SCU-CP is easier to apply in the field and more environmentally friendly than the common method. SCU-CP method was proven to impact sandy soil and peat soil significantly, but SCU-CP’s impact on expansive soil still needs to be discovered. This study aims to know the effects of SCU-CP on soil swelling parameters and determine the optimum reagent concentration for expansive soil improvement using SCU-CP. This study used three reagent concentrations (1.0 mol/L, 1.5 mol/L, and 2.0 mol/L) and one control sample (without SCU-CP). The swell percentage decreased by 2 – 3% after SCU-CP treatment, but adding reagent concentration did not significantly reduce the swell ratio. Swell pressure did not decrease after SCU-CP treatment. Swell pressure was only reduced by 7.92 kPa with 1.0 mol/L reagent of SCU-CP, while the other concentration swell pressure tended to be increased. This study’s optimum reagent concentration for expansive soil improvement is 1.0 mol/L.