Mineralization effects of microbially-induced calcite precipitation: Influencing factors, microstructural characterization, and self-healing effect on SHCC

Strain-hardening cementitious composites (SHCC) develop multiple microcracks under tensile or flexural loading, which accelerates the ingress of aggressive agents. Microbially induced calcium carbonate precipitation (MICP) offers a promising route to enhance the self-healing of such crack networks. This study innovates by systematically coupling key MICP parameters, such as bacterial suspension-to-cementation solution ratio, calcium source, and Ca²⁺ concentration, and directly translating the optimized mineralization condition into a practical spray-based crack-healing protocol for SHCC. The mineralization products were characterized using SEM, EDS, XRD, and elemental mapping. The results show that mixing ratio and Ca²⁺ concentration strongly govern CaCO₃ quantity and morphology. At 1.5 mol/L, calcium acetate produces higher mineralization performance than calcium chloride and calcium nitrate under the tested conditions. In SHCC specimens, five spray treatments with 1.5 mol/L cementation solution achieved complete surface crack closure (100% healing rate) and markedly reduced capillary absorption. This study provides insights into the key factors affecting MICP mineralization in cementitious systems and offers practical guidance for optimizing microbial self-healing agents in construction materials.