Study on improving the self-repairing effect of cement-based materials by microbial mineralization coupled with inorganic minerals

As a green and intelligent method, the self-repairing technology based on microbial mineralization had obvious defects. In this study, microbial mineralization coupled with inorganic minerals was used to realize the full-depth repair of cracks in cement-based materials, and the feasibility was systematically demonstrated. The self-repairing carrier with multilayer core-shell structure was prepared, and the average particle strength was 36.12 N; Protective layer was composed of hydrated calcium silicate, hydrated calcium aluminate and other hydration products, which had relatively dense structure. Compatibility between microorganisms and carrier was deeply studied, and the growth performance of microorganisms after long-term storage was basically equivalent to that of the initial microorganisms. Composition and microstructure of products in crack area were studied by X ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS), and products were mainly composed of calcium carbonate and ettringite with particle sizes of approximately 5–10 µm.The repair effect was studied by stereomicroscope, X ray computed tomography (X-CT) and ultrasonic detector. A large number of products were deposited on the two surfaces of the specimen, the crack was effectively filled; In addition, more products were deposited around the carrier, and a large number of cracks were repaired. Based on the above research, repair mechanism of the full-depth was identified. Microbial mineralization was mainly committed to the repair of crack surface, while ettringite prepared by inorganic reaction could repair the interior of crack, and the combination of the two paths could achieve the full-depth repair.