Desiccation cracking remediation through enzyme induced calcite precipitation in fine-grained soils under wetting drying cycles

Abstract

The effects of desiccation cracking in clay soils on geotechnical constructions are substantial. This study investigates the viability of utilizing Enzyme-induced calcite precipitation (EICP), a bio inspired approach, as a potential solution for addressing desiccation cracking in fine-grain soils. For the EICP technique, crude soybean extract is employed for the purpose of urea hydrolysis. Multiple fluid samples, including a control sample, a cementation solution containing 1 M urea, 0.675 M CaCl₂, and 4 g/L milk, along with various concentrations of enzyme solutions (3–80 g/L), were tested for the study. To evaluate the surface cracking patterns, the method involved constant monitoring and photo recording using a high-resolution camera aided by image processing software. The results showed that fine-grain soils improved from increased calcite precipitation and decreased desiccation cracking intensity when the EICP method was used. Cementation and enzyme solution with low concentrations (3 g/L and 10 g/L) had similar effects on crack remediation, suggesting a modest influence. In contrast to the sample treated with water, the crack network remained unaltered in this case. CaCO₃ precipitation within the void area kept the crack network in place even as the void thickness decreased at increasing enzyme concentrations (30 g/L, 50 g/L, and 80 g/L). Wetting and drying cycles were found to decrease the crack ratio, crack width, and crack length in the EICP-treated sample, particularly under higher concentrations of urease enzyme. Lower enzyme concentrations of 3 g/L and 10 g/L have minimal impact on crack remediation but effectively inhibit new crack formation. Furthermore, higher enzyme concentrations result in calcium carbonate precipitates, forming a soil crust and increasing surface roughness. The study aims to enhance understanding of the EICP methodology and to provide novel perspectives on potential uses for soil enhancement.