Effects of SiO2 with Different Particle Sizes on the Self-Repairing Properties of Microbial Mineralized Cement Mortar

Microbial-induced calcium carbonate precipitation (MICP) is an environmentally sustainable technology for the self-healing of concrete cracks. In this experiment, expanded perlite was used as a bacterial carrier. It can facilitate the adsorption of bacteria and serves as a self-healing agent when incorporated into cement mortar. Two different sizes of silica were simultaneously added to evaluate the combined effects of the self-healing agent and varying silica sizes on the mechanical and self-healing properties of cement mortar. The objective is to determine the optimal dosage for each silica size. The results show that the self-healing agent can improve the density and strength of the structure in the early stages of maintenance and realize the self-healing of microcracks after the cement mortar has cracked. Adding a single particle size of silica at the optimal dosage can effectively improve the strength of cement mortar. Adding two different sizes of silica can optimize the particle grading of silica. Nano-sized silica is beneficial to improving the early compressive strength of cement mortar, and micron-sized silica is beneficial to improving the self-healing efficiency of cement mortar and completely sealing cracks at an early stage. The interaction between silica particles of varying sizes can further enhance the mechanical and self-healing properties of cement mortar. Microscopic observations and tests provide effective support for these conclusions and elucidate the mechanism of interaction between the self-healing agents and silica.