Mechanistic Study of Sodium Silicate–Enhanced MICP for Rapid Sandy Soil Stabilization

Microbially induced carbonate precipitation (MICP) is a highly promising method for soil reinforcement. However, as research on this technology has advanced, several shortcomings have become increasingly apparent, including prolonged treatment durations and relatively low efficiency. To address these issues, this study employed sodium silicate as an additive in the MICP process and investigated its effects on the reaction. The results showed that adding an appropriate amount of sodium silicate to the bacterial solution enhanced the quantity of calcium carbonate precipitation. The sand column samples solidified rapidly after just two treatment cycles; after 10 treatment cycles, the sand column treated with sodium silicate showed a one-order-of-magnitude reduction in permeability coefficient and achieved a strength of 5.9 MPa—representing a 694% increase compared with conventional MICP-treated samples. Microscopic tests demonstrated that the addition of sodium silicate led to the formation of calcium silicate hydrate (C─ S─ H) gel. This gel effectively filled the pores in the sand and cemented the sand particles, consequently enhancing the strength and reinforcement efficiency of the sample. The findings provide valuable insights for the advancement and implementation of microbial sand reinforcement techniques.