Polymer-modified microbially induced carbonate precipitation for one-shot targeted and localized soil improvement

The viscous nature of certain hydrophilic polymer solutions and the tendency of these solutions to retain moisture may make them suitable carriers for the process of microbially induced carbonate precipitation (MICP) for certain engineering proposes. Specifically, tuning the viscosity of the cementation solution enables the control of its infiltration process and thus control of the treatment region in highly permeable soils; the enhanced water retention also helps to maintain the moist conditions required for MICP in certain treatment cases. Therefore, it seems promising to utilize a hydrophilic polymer to develop a one-shot polymer-modified MICP approach for potential applications that require localized and targeted soil improvement. Presented in this paper are experiments conducted to investigate a new polyvinyl alcohol (PVA)-modified MICP approach. Standard Ottawa graded sand was treated using both polymer-modified and conventional water-based MICP solutions with different concentrations of cementation media. For the obtained specimens, the chemical components were identified through thermogravimetric analysis, the CaCO₃ content was measured, and unconfined compression tests were conducted to evaluate the shear strength. The morphology, distribution, and crystal polymorphs of the precipitated CaCO₃ were also characterized. The experimental results demonstrated the feasibility of the proposed polymer-modified MICP approach as a one-shot MICP treatment scheme. Moreover, two bench-scale soil improvement cases were conducted to highlight the advantages of the proposed polymer-modified MICP approach over the water-based approach for certain potential soil improvement applications.