Reinforcement mechanism of coal-based solid waste slurry-rock interface through microbial mineralization by Sporosarcina pasteurii

Abstract

The utilization of coal-based solid wastes (CSW) as cementitious materials offers significant potential for reducing cement consumption and environmental burden in mining and construction. However, its low hydration activity and weak interfacial transition zone (ITZ) often limit performance. This study investigates the enhancement of slurry-rock interface (SRI) properties in CSW systems through microbially induced calcium carbonate precipitation (MICP) using Sporosarcina pasteurii. Consolidated specimens containing a single SRI were prepared and tested by splitting tensile and direct shear tests, while their microstructural and micromechanical characteristics were examined using SEM and nanoindentation. Compared with the sterile control, microbial mineralization increased the interfacial splitting tensile strength by 61.5% and raised the direct shear strength from 1.45 to 1.80 MPa under a normal stress of 3 MPa. The strengthening effect was lithology-dependent, with limestone and sandstone showing higher interfacial strengths than mudstone. Increasing the joint roughness coefficient further improved bonding performance, with the maximum shear strength reaching 5.08 MPa. Nanoindentation results showed that microbial treatment eliminated the distinct weak ITZ of 7.4–20 µm observed in sterile samples, indicating improved interfacial compactness and micromechanical uniformity. These findings clarify the microbial strengthening mechanism of SRI in sustainable CSW-based grouting materials.

Keywords

coal-based solid wastes (CSW) / slurry-rock interface / nanoindentation / microbial mineralization / shear strength

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