Enhancing Shear Strength of Sandy Soils Using Enzyme-Induced Carbonate Precipitation and Sodium Alginate Biopolymer

This study investigates a laboratory-based approach to improving the shear strength of sandy soils through enzyme-induced carbonate precipitation (EICP) enhanced with sodium alginate biopolymer. To reduce reliance on costly commercial urease, a simplified extraction method was developed using watermelon seeds, an underutilized agricultural byproduct, with natural separation replacing centrifugation. The hybrid stabilization process incorporated sodium alginate at 0, 0.5, 1.0, and 1.5% of the EICP solution. Direct shear testing revealed significant strength improvements, with cohesion increasing from 0 kPa in untreated soil to 60 kPa at 1.5% sodium alginate, while the internal friction angle rose from 43.4° to 45.3°. Microstructural analyses confirmed dense calcite networks and characteristic carbonate bonds, validating effective bio-cementation. While these laboratory findings highlight the potential of the proposed technique, further research, including cost analysis, sustainability assessment, and field-scale feasibility studies, is required before drawing conclusions on its broader acceptability compared to conventional stabilizers.