Mineral Evaluation and Undrained Cyclic Shear Response of MICP-Treated Sand in the Presence of Magnesium and Sulfate

Abstract

Microbially induced carbonate precipitation (MICP) has attracted considerable interest as an innovative technology that improves soil’s stiffness and strength via CaCO3 precipitation induced by microbial metabolic activity. Mg2+ and SO42− are known to inhibit CO3-based mineral precipitation. In this study, MICP was conducted in the presence of Mg2+, SO42−, and salt water to investigate their effects on mineral formation and the undrained shear response of the soil. The MICP treatment process was conducted within soil columns and cyclic direct simple shear devices. The undrained cyclic shear response was evaluated for untreated and treated sand specimens. Chemical equilibrium and analytical models were used to compare the predicted mineral precipitation with experimental results. The results indicated that the presence of Mg2+, SO42−, and salt water lead to different mineralogies and mineral morphologies, and undrained shear responses of MICP-treated sand. During the MICP process, the presence of Mg2+ and salt water enhanced the level of cementation and liquefaction resistance, whereas the presence of SO42− inhibited the formation of CaCO3 with an insignificant change in liquefaction resistance.