Healing Technique for Rock Cracks Based on Microbiologically Induced Calcium Carbonate Mineralization

Abstract

Rock mass is a structural system with intact rock cut by cracks. The properties and strength of cracks determine the macroscopic mechanical properties of rock mass. Improving the self-stability of rock mass by enhancing the shear strength of the cracks is currently a cutting-edge topic in the geotechnical field. As a new reinforcement method for cracks, biological healing technique has attracted much attention. This paper applies bacteria-induced calcium carbonate mineralization to heal cracks in migmatitic granite and conducts relevant mechanical tests. Sporosarcina pasteurii (lyophilized powder) is activated in the laboratory and used to induce calcium carbonate mineralization on a crack in migmatitic granite. Healing and reinforcement of cracks is realized. The mineralization products on the crack are observed using X-ray diffraction and scanning electron microscopy. The mineralization products are bacteria-induced calcium carbonate precipitates. The crystals are cubic in shape with a side length of about 5–1 μm and helical dislocation structure. At this moment, the cracks in migmatitic granite are completely cemented. Finally, shear tests are conducted on the healed and reinforced cracks. The tests results indicate that bacterially induced calcium carbonate mineralization can greatly improve the shear stiffness, peak shear strength, and residual strength of cracks, and the healing effect is time-dependent. The results of this study show that the bacterially induced mineralization technique not only can enhance the integrity of the rock cracks, but also can significantly improve the shear capacity of the cracks. This healing technique can provide new ideas in reinforcing cracks in rock masses.