Bio-cementation of sand using enzyme-induced calcite precipitation: Mechanical behavior and microstructural analysis
Amali Gitanjali, Yu-Syuan Jhuo, Fu‐Hsuan Yeh, Louis Ge
Abstract
The enzyme-induced calcite precipitation (EICP) has recently gained popularity as a ground improvement technique. Bio-cementation via EICP increases the strength , stiffness, and soil liquefaction resistance by clogging the voids and binding the soil particles with calcium carbonate . The objectives of the study involve assessing the mechanical behavior of the EICP-treated sand by performing monotonic consolidated drained triaxial and undrained cyclic triaxial tests . This study adopted a one-phase EICP cementation solution consisting of 1 M Urea, 0.67 M Calcium chloride dihydrate, and 3 g/l urease enzyme. The monotonic triaxial tests on pure sand and EICP-treated sand with 3,7, and 14 curing days were carried out at 50, 100, and 200 kPa confining pressures, respectively. A noticeable effective cohesion was observed for EICP-treated sand for all curing durations. Undrained cyclic triaxial tests on the EICP-treated specimens with 7 days of curing were performed at an effective confining pressure of 100 kPa. As expected, the number of cycles to liquefaction was higher in the EICP-treated specimen compared to pure sand due to the cementation effect. Finally, scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) mapping confirmed the enhanced liquefaction resistance in EICP-treated sand due to calcium carbonate precipitation, leading to particle-to-particle interlocking. Additionally, X-ray Diffraction (XRD) analysis revealed the presence of calcite crystals resulting from the EICP treatment.