Review of Strength Improvements of Biocemented Soils

Microbially induced calcium carbonate precipitation (MICP) has attracted great attention recently for its ability to improve the mechanical properties of soils. Calcium carbonate (CaCO3) precipitates that formed at the contact points and on the surface of particles or in the pore space of soil matrixes could increase the bonding strength, friction, and interlocking resistances due to the enhancement of the interparticle bonds, particle roughness, and packing density, and therefore, greatly improve the macroscopic performances of biocemented soils that were subjected to external loading. Strength is one of the key factors when determining the application of biotreatments in geotechnical engineering during the construction and operation periods. This study presented a systematic, objective, and extensive review of the strength of biocemented soils that was based on previous research. The improvement characteristics were comprehensively investigated under compression, tension, and static and cyclic shear conditions, for unconfined compressive (UCS), splitting tensile (STS), yielding, shear, and cyclic resistance strengths. Particle scale regimes were elaborated to interpret the improvement mechanism in the biotreatment and failure modes in biocemented specimens under external loading. Furthermore, the challenges of biocementation were discussed, and future investigations were envisioned. This work is made available under the terms of the Creative Commons Attribution 4.0 International license, https://creativecommons.org/licenses/by/4.0/.

Automated summary

Microbially induced calcium carbonate precipitation (MICP) improves the mechanical properties of soils by increasing bonding strength, friction, and interlocking resistances. This study comprehensively investigates the strength characteristics of biocemented soils and discusses the challenges and future directions of biocementation.