Self-healing performance of silica nanoparticle-infused concrete based on microbial mineralization

This study investigates the effects of incorporating two substances-expanded perlite as a carrier for bacteria and nanosilica-into cement mortar. The objective of this study is to evaluate the effect of the dosage of these two substances on the strength and self-healing properties of mortars. The strengths of the specimens at different curing ages are tested using a pressure-testing machine and recorded. Additionally, precracks are introduced into the specimens. The cracks and their healing products are observed via electron microscopy, scanning electron microscopy, and X-ray diffraction to validate the experimental results. The results show that the self-healing agents agglomerate at the cracks and trigger a metabolic reaction, thus resulting in the formation of numerous calcium carbonate precipitates that sealed the cracks. Therefore, the addition of self-healing agents significantly improves the self-healing properties of the cement mortar. The nanosilica facilitates the hydration reaction of cement in mortar. Additionally, nanosilica undergoes a pozzolanic reaction with calcium hydroxide, which consumes calcium hydroxide and generates hydrated calcium silicate to fill the pores. Consequently, the incorporation of an appropriate amount of nanosilica effectively enhances the strength of the cement mortar. Therefore, simultaneously incorporating self-healing agents and nanosilica while controlling the dosage provides a new approach for optimizing both the mechanical properties and self-healing performance of concrete.