The influence of expanded perlite as a bio-carrier on the freeze–thaw properties of self-healing concrete

Microbial mineralization technology enables self-diagnosis and healing of concrete cracks; however, its internal alkaline environment and dense structure make it necessary to use a reasonable method to protect the bacteria. Two bacterial self-healing agents were prepared by encapsulation and non-encapsulation methods using expanded perlite as a carrier, and their effects on concrete performance and post-freezing healing were investigated under freeze–thaw cycling conditions. The results showed that the non-encapsulated self-healing agent improved the resistance of concrete to freeze–thaw action, while the self-healing agent prepared by the encapsulation technique exhibited negative effects. After 100 freeze–thaw cycles, the self-healing ability of concrete was reduced, but it remained effective in repairing cracks smaller than 0.45 mm. The best effect was achieved when the two self-healing agents were added in the ratio of 1:1, with the maximum healing width reaching 0.757 mm and the maximum repaired width after freezing was 0.6426 mm. The results of this study can be used as a scientific basis for the application of microbial self-healing technology in cold regions.