Self-healing performance of concrete for underground space

Endowing concrete with self-healing properties is one of the effective methods to improve its durability. In this study, biocapsules and mineral capsules were premixed in cement mortar and cured in wet dry cycles and simulated underground space environment. The self-healing performance of cement-based materials in underground engineering, especially in underground coal mine spaces, and the synergistic effect of biocapsules and mineral capsules on crack repair were studied through indicators such as crack healing efficiency, water absorption, water permeability and air permeability. The study found that the crack healing rate of samples cured in the simulated underground space is lower than that cured in the wet dry cycles. The synergistic repair of cracks of the samples with biocapsules and mineral capsules is reflected in the recovery of bacterial spores, and the mineral capsules can repair the cracks, thereby ensuring that the cracks are in a self-healing state during the entire curing cycle. After healing, the gas barrier of samples with biocapsules and mineral capsules is 8.55-8.69% higher than that of sample only with fibers. The healing product of the samples with biocapsules is spherical calcite-type calcium carbonate, and the healing product of the samples with mineral capsule is the rose-shaped hydromagnesite.