Bentonite-assisted microbial-induced carbonate precipitation for coarse soil improvement

Microbial-induced carbonate precipitation (MICP) is a promising technique to reinforcconclusione soils utilizing the metabolic process of bacteria. MICP can be utilized in coarse-grained soil and result in calcium carbonate precipitation among soil particles, thus improving the mechanical properties. However, the reinforcement efficiency decreases as the particles become coarser, and multiple injections are required for a better outcome. It would not be cost-effective for coarse soils to achieve high strength or low permeability via this method. In this study, bentonite was utilized together with MICP to improve coarse soil properties. For sand treated by bentonite-assisted MICP, the quantity of precipitated calcium carbonate was measured, and the precipitate microstructure was assessed; the mechanical behaviors, including permeability and unconfined compression strength, were evaluated. The experimental results demonstrated the feasibility of the proposed bentonite-assisted MICP method. With the introduction of bentonite, the bacterial activity retention of soil subsequently increased, resulting in more production of calcium carbonate with an unchanged crystal type. The permeability was remarkably reduced, and the strength was improved by the enhanced bioclogging and biocementation effects. In addition, no volumetric swelling was observed for sand treated with bentonite-assisted MICP, and the water-resistance ability was improved with a lower water absorption ability.

Automated summary

The study utilized bentonite-assisted MICP to improve coarse soil properties, resulting in enhanced mechanical behaviors and reduced permeability.