Effect of Calcium Source on Sand Bio-Cementation

In this study, the effect of different calcium sources on microbial calcium carbonate precipitation (MICP) was investigated. Three calcium sources, including calcium chloride, calcium nitrate, and calcium acetate, were selected based on their applicability and solubility. The fall cone tests and triaxial consolidated-drained tests were performed at the same proportion of calcium to urea, 1:1, with the concentration 0.5 M, and single-phase injection. The results indicated that the uniformity of specimen was increased by controlling the pH value of MICP treatment solution at 8.50-8.70 before injecting the solution into the specimen. Calcium nitrate exhibits the highest calcite content in treated specimens. On the consolidated-drained triaxial tests, peak strength is positively correlated with calcite content at confining pressure 100 kPa. However, calcium chloride specimens showed the lowest penetration depths in the fall cone test, which may be due to the matric suction under partially saturated condition. It may be concluded that saturation affects the effectiveness of improvement of different calcium sources.