Durability Evaluation of MICP-Repaired Concrete Exposed to the Freeze–Thaw Process

Traditional methods for repairing concrete cracks using inorganic and organic polymer materials have shown unsatisfactory performance in engineering practice and have also led to significant environmental pollution. However, microbial induced calcium carbonate precipitation (MICP) has been proven to be a clean technology for crack repair in concrete, with the added benefit of improving its mechanical properties. One crucial aspect to consider is the impact of the freeze–thaw process on the durability of concrete. Therefore, it is vital to assess the freeze–thaw durability of MICP-repaired concrete. This study first evaluated the efficiency of crack repair using MICP through water permeability and electrical flux tests. Subsequently, the changes in the apparent morphology, mass, and permeability of MICP-repaired concrete specimens were investigated after undergoing freeze–thaw process in order to assess their durability. The results indicated that mineralized calcium carbonate effectively filled the cracks, enhancing the compactness of the concrete and significantly improving its resistance to freeze–thaw process. The filling of cracks with calcium carbonate alerted the freeze–thaw erosion path in the concrete specimens. Additionally, it was found that increasing the initial width and depth of cracks weakened the impact of MICP on the freeze–thaw erosion resistance of cracked concrete.