Microbial Induced Calcite Precipitation & Biogeotechnical Soil Stabilization: Ureolytic Kinetics, Reactive Transport Mechanics, and Biocementation Dynamics
Microbial Induced Calcite Precipitation (MICP) and biogeotechnical soil stabilization utilize biological enzymatic pathways to precipitate calcium carbonate ($\text{CaCO}_3$) crystals within the pore network of weak soil matrices. By converting loose, liquefiable sands or soft soils into bio-cemented sandstone-like media, MICP increases shear strength, enhances stiffness, and reduces hydraulic conductivity without relying on carbon-intensive synthetic chemical grouts or traditional Portland cement injection. The primary bio-chemical mechanism behind MICP relies on ureolytic bacteria (such as Sporosarcina pasteurii ) producing the enzyme urease, which hydrolyzes urea ($\text{CO(NH}_2)_2$) into dissolved ammonium and carbonate ions: $$\text{CO(NH}_2)_2 + 2\text{H}_2\text{O} \xrightarrow{\text{Urease}} 2\text{NH}_4^+ + \text{CO}_3^{2-}$$ In the presence of introduced calcium ions ($\text{Ca}^{2+}$), calcium carbonate precipitates onto negative bacterial cell walls acting as nucleat...