Water Glass Modified Bioslurry for MICP under High Concentrations Calcium: Rapid Strength Development

High Ca2+ adaptable is vital for rapid strength development of biocementation in CO2 leak sealing and ground stabilization. However, existing additive-modified approaches fail to mitigate high Ca2+ inhibition on bacteria activity. This two-part study develops a novel bioslurry compatible with high concentration calcium: Part I focuses on material and macroscale performance optimization, and Part II explores high Ca2+ tolerance mechanisms. In Part I, the novel bioslurry prepared via the reaction of water glass and calcium chloride formed an amorphous calcium silicate hydrate matrix that encapsulates bacteria. Concentration confocal laser scanning microscopy (CLSM) and Nessler tests confirm that 1% water glass ensures excellent biocompatibility and significantly boosts specific urease activity. Tube and sand column tests examined the impacts of water glass concentration, urease activity, and cementation solution concentration (CCS) on CaCO3 precipitation and unconfined compressive strength (UCS). Results show the bioslurry effectively mitigates Ca2+ inhibition, achieving 90% Ca2+ conversion at 2.5 mol/L CCS, which represents a 394.4% increase over the control. Two treatments with 1% water glass increased UCS by 2314.2% over the control at 2.5 mol/L CCS to a peak of 10.4 MPa, whereas single treatments reached a maximum of 4.37 MPa and correlated primarily with CaCO3 content.