Microbially induced calcite precipitation (MICP) utilises ureolytic bacteria to precipitate CaCO 3 within soil pores, thereby sustainably altering shear strength and permeability. However, the properties of biocement crystal, such as its size, amount, and mineralogy, vary based on biomass concentration ( B 0 ), cementation reagent concentration ( C 0 ), and solution pH. The quantitative influence of these biochemical parameters and their coupled effect on crystal features remain unaddressed. Given this, by varying the reaction solution’s B 0 , C 0 , and pH through robust experimental design and reaction-kinetic modelling, the present study optimised crystal size, quantity, and mineralogy to accomplish maximum soil strength. The results revealed that increased C 0 at lower B 0 favours crystal growth, but becomes unfavourable at excessive biomass. Similarly, lower B 0 precipitates bigger crystals, but lag time at decreased pH promotes bacterial growth, becoming detrimental to crystal size. Besides, the elevated B 0 produces unstable vaterite minerals, while an increment in C 0 inhibits bacterial urease activity, leading to stable calcite mineral precipitation. For the optimised biochemical parameters ( B 0 = 0.25 OD 600 , C 0 = 1 mol/L, and pH = 9), soil biocementation tests confirmed the enhancement of surface crust strength up to 10.13 MPa due to larger crystal size. Incorporating novel encapsulation effects and thermally altered urease activity in reaction kinetic modelling led to reasonable corroboration between numerical and experimental calcite precipitation amounts in both isothermal and varied temperature conditions. Overall, this study quantified the intricate interplay of biochemical parameters in controlling crystal characteristics and ultimate strength, providing a comprehensive approach to optimising the MICP process for potential field-scale applications.
Joshi et al. (Sun,) studied this question.