Preparation of Magnetic Microbial Repair Material and Its Application in Concrete Crack Healing

Abstract Due to its high brittleness and low tensile strength, concrete is vulnerable to cracks, which will compromise the safety and service life of a structure. Although microbial repair materials have gained attention for their compatibility with concretes and their eco-friendly nature, they have limitations, such as a restricted repair depth and width, and the inability to repair complex or small cracks. In this work, we prepare a magnetic microbial repair material consisting of two components. Component A comprises a magnetic microorganism–sodium alginate (SA) composite, which can flow under a magnetic field, and Component B is composed of calcium acetate and urea. By optimizing the concentrations of the comprising materials, an effective and efficient healing of penetrating cracks is achieved. The results show that the magnetic microbial repair material exhibited the best healing effect for the smallest cracks studied in this work, which were 20 mm long, 5 mm wide, and 100 mm deep. After healing for 7 days, the water absorption rate decreased by 20.8%, and the compressive strength recovery rate was as high as 99.7%, confirming the applicability of this magnetic microbial repair material in healing small, deep cracks.