Effect of urease enrichment degree of multiple sources of urease on bio-cementation efficacy via enzyme-induced carbonate precipitation

Abstract

This study aims to investigate the effect of the urease enrichment degree of high-purity commercial urease and plant-derived crude ureases from sword bean (SWCU), soybean (SCU), and pigeon pea (PCU) on bio-cementation efficacy via enzyme-induced carbonate precipitation. The urease enrichment degree is defined as the urease activity per gram of organic matter in the urease solution. Bio-cementation efficacy was evaluated by the distribution and morphology of the precipitates and unconfined compressive strength. The results show that the urease enrichment degrees of the high-purity commercial urease, SWCU, PCU, and SCU are 1.08, 1.05, 0.57, and 0.31 mmol/min/g, respectively. The urease enrichment degree is the dominant factor influencing the pattern of CaCO3 distribution by affecting the organic matter distribution. The high-purity commercial urease-treated sand has the smallest calcite crystals (13–23 µm) and the lowest strength (172 kPa). For the plant-derived crude urease, with the decrease of the urease enrichment degree, the generated crystals become smaller, the CaCO3 distribution becomes less uniform, and the soil strength decreases. The SWCU-treated sand exhibits the best bio-cementation efficacy and is recommended to enhance soil strength.