Research on performance and engineering application of spray air leakage plugging self-healing material for mining

Spray air leakage plugging is one of the effective means to prevent coal spontaneous combustion. Aiming at the drawbacks of high brittleness, easy cracking, and poor air leakage plugging effectiveness of traditional cement-based spraying air plugging material, biological capsule, mineral capsule and bio-mineral-fiber synergistic self-healing material were developed with microorganisms and crystalline minerals as self-healing agents. The influence of different curing humidity and curing time on the self-healing ability of material cracks was studied. The results showed that when the curing humidity was 100%, and the curing time was 35 days, the biological and mineral capsules could completely heal the cracks, with a maximum healing width of1260μm. Scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS) were used to investigate the crystal structure and elemental composition of the healing products in the crack area of self-healing material. It was found that the healing products at the crack were spherical magnesite, petal-shaped hydromagnesite, and a large amount of spherical calcite produced by bacterial mineralization, which to some extent played a role in sealing the crack. EDS analysis confirmed that the healing products were MgCO₃ and CaCO₃. When the curing humidity was 100%, the material had the highest air leakage plugging rate (97.15%), which was 73.62% higher than the control group samples under the same curing conditions. Finally, self-healing material was used for spraying and plugging air leakage along the coal pillar, and the results showed that no obvious cracks were found within 6 months. Compared with traditional cement mortar, self-healing material has a longer service life and better prevention effect.