Research of Enzyme-Induced Carbonate Precipitation on Strength Behavior of Reinforced Sand

Stabilizing sandy soil with inadequate engineering properties is essential for constructing infrastructure systems in all regions, especially in desertification-prone areas. Enzymatically Induced Carbonate Precipitation (EICP) offers an innovative solution, with advantages over conventional soil reinforcement methods due to its low energy consumption and carbon emission. This emerging reinforcement technique has proven effective in enhancing soil strength, yet the effects of variables such as curing time and cementation solution concentration, and their micro-mechanistic implications on sandy soil, remain understudied. This study conducted a series of unconfined compressive strength (UCS) tests and microstructural analyses on EICP-treated sand. The results showed that the optimal curing time for EICP-reinforced sand is seven days, with its strength being contingent upon soil density. The maximum UCS value was observed at a relative density of 0.7 and a cementation solution concentration of 1 mol/L. Mechanistically, EICP strengthens soil integrity through calcium carbonate-mediated cementation and particle bridging, thereby boosting soil strength. Micro-CT imaging and fractal dimension analyses reveal that the precipitation process decreases both the size and connectivity of the pores, while simultaneously increasing their surface heterogeneity and enhancing the overall toughness. This research establishes a foundational framework for advancing EICP applications in soil stabilization engineering.