Damage-healing model for self-healing cementitious materials

Microbially induced calcium carbonate precipitation (MICCP) is a bacterial metabolic process that precipitates calcium carbonate (CaCO3) in the presence of nutrients and calcium sources. This process has significant potential for healing concrete structures by crack filling. An uncoupled damage-healing model is developed to predict the fracture-healing response of self-healing concrete. The model consists of two components: (1) an MICCP healing model based on enzymatic and chemical kinetics and (2) a finite element method (FEM) fracture model based on the phase-field method (PFM). The results of the MICCP model, which governs the degree of healing (healing efficiency) in a damaged structure, are integrated into the PFM simulation to capture crack initiation, propagation, and the force-displacement relationship of a healed concrete structure under reloading.

In this study, a three-stage computational scheme is established. In Stage 1, the damage in a concrete structure is simulated using the conventional PFM with a staggered computation scheme. In Stage 2, the concrete structure is unloaded. It is assumed that the necessary microbes, nutrients, and chemicals are readily available at the crack sites, initiating the MICCP process. The damage variable at the material points of each element is then updated (recovered) based on the healing efficiency​ derived from the MICCP model. Finally, in Stage 3, the updated damage variable is incorporated into the original model, and reloading is applied to simulate the damage evolution of the healed material. The load-displacement curve of the healed material, corresponding to different degrees of healing, is obtained.