Water Glass Modified Bioslurry for MICP under High Concentrations Calcium: LF-NMR Insights into High Ca 2+ Tolerance

Clarifying the transport and precipitation in porous media is essential for high Ca 2+ MICP cementation in engineering. In part Ⅰ, a series of material optimization and strength tests were conducted, but the intrinsic dynamic evolution mechanisms of high Ca 2+ tolerance remain insufficiently explored. This study integrates Low-field nuclear magnetic resonance (LF-NMR) with D2O and Mn 2+ molecular probes and a dual chamber PTFE mould to visualize the spatiotemporal evolution of Ca 2+ migration, dynamic evolution of Ca 2+ concentration and CaCO 3 precipitation in a bioslurry enhanced MICP reaction. Results indicate that the cementation solution, driven by concentration gradients, initially propagates along preferential pathways such as solid-liquid interfaces and sidewalls before extending toward the column center. Higher solution concentrations accelerate diffusion and produce a curved diffusion front. CaCO 3 precipitation exhibits a consistent spatiotemporal pattern, and the addition of water glass mitigates Ca 2+ inhibition, enabling sustained MICP reaction. A calibrated T 2 weighted signal intensity-Ca 2+ concentration relationship was established to enable quantitative tracking of Ca 2+ dynamics.