Performance and Mechanism of Enzyme-Induced Carbonate Precipitation (EICP) for Fine-Grained Saline Soil Stabilization

In coastal saline soil regions, foundation instability frequently arises due to salt heave, dissolution-induced weakening and corrosion-driven degradation. To enhance the engineering performance of fine-grained saline soil, this study evaluates the effectiveness of Enzyme-Induced Carbonate Precipitation (EICP) treatment under varying salinity levels and curing solution concentrations. Mechanical properties, hydraulic behavior and water stability were examined through unconfined compressive strength (UCS), disintegration and permeability tests, complemented by microstructural analyses using XRD and SEM. The results indicate that EICP notably improves mechanical strength, water stability and reduced permeability. The UCS of treated specimens increased by 37–152% relative to untreated soil, and disintegration time was prolonged by 214–563%. The permeability coefficient was reduced by 45.8–95.7%, demonstrating effective suppression of seepage channels. The optimal stabilization performance was achieved at 0.02% salinity and curing concentrations of 1.0–1.3×. Excessive salinity distorted vaterite crystal morphology and weakened cementation. XRD and SEM analyses revealed that vaterite dominated the calcium carbonate polymorphs, while ionic complexity influenced crystal structure, ACC conversion and pore-filling performance. These findings confirm the feasibility of applying EICP for improving fine-grained coastal saline soils and provide practical engineering guidance for coastal subgrades, reclamation foundations and port infrastructures.