Phase-field pore-scale study of microbial-induced calcium carbonate precipitation: Integrating flow, reactive transport, and precipitation dynamics

Microbially induced calcium carbonate precipitation (MICP) is a sustainable and effective geotechnical reinforcement technique, with its performance strongly dependent on the spatial distribution of CaCO 3 . Existing pore-scale models inadequately capture the two-way feedback between CaCO 3 morphological evolution and local hydrodynamics, thus failing to account for the effect of fluid shear stress on crystal growth. This study developed a comprehensive pore-scale model for MICP, integrating fluid flow, reactive transport, and precipitation mechanisms. By employing the phase-field method, the model simultaneously captures interfacial precipitation and the regulatory effect of shear-induced erosion on crystal development. The model resolves the detailed spatiotemporal dynamics of CaCO 3 growth and flow redistribution, enabling quantification of inter-particle cementation areas. Validation against microfluidic experiments showed close agreement between simulations and measured results. Using the validated model, the effects of injection rate, concentration, and pore-network heterogeneity on the spatial distribution of CaCO 3 and permeability were investigated. The results indicated that the highest CaCO 3 precipitation (approximately 60.0 %) occurred at Pe = 9.0, and the normalized effective permeability reduction reached approximately 0.5 for the cases investigated. Increasing the solution concentration from 0.25 to 1.0 M increased the CaCO 3 proportion from 53 % to 80 %, but decreased the normalized effective permeability to 0.24 and induced repeated reversals in regional precipitation differences. Higher pore-network heterogeneity expanded the precipitation range and increased the total CaCO 3 proportion, and produced inter-particle bonding-area distributions that were more consistent with experimental observations. These findings provide a reference for incorporating spatially non-uniform CaCO 3 cementation into discrete-element modeling of MICP-treated granular materials.