Prediction of microbial-induced calcium carbonate precipitation for self-healing cementitious material

Microbial-induced calcium carbonate precipitation (MICCP) is a biomineralization process utilizing microbial metabolic activities to precipitate calcium carbonate (CaCO₃). In recent years, there has been increasing interest in the application of MICCP in self-healing cementitious materials. In this research, the chemical and enzyme kinetics of MICCP were numerically modeled, focusing on the ureolytic bacteria responsible for the ureolysis reaction, which facilitates the precipitation of CaCO₃. The model considers the growth and decay of bacteria, the ureolysis reaction catalyzed by the urease enzyme of the bacteria, the shift in bicarbonate equilibrium due to pH variation of the solution, and the calcium carbonate precipitation. In the simulation, the concentration of chemicals and bacteria as a function of time was computed. Additionally, the distribution of chemicals due to fluid transport were determined. The capability of the model was demonstrated through several benchmark simulations, including its application in self-healing concrete with a vascularized channel system. Experimental studies were also conducted to first calibrate the model parameters and then validate the model results. The predicted CaCO₃ precipitation defines a crack filling ratio, $h_d$, which is discussed in many damage-healing literature. Once the mechanical properties of MICCPs are determined, the strength recovery of self-healing concrete incorporating MICCP can then be further modeled.