Development and performance characterization of a composite grouting material suitable for sealing and reinforcement of microcracked mudstone

Micro-pore grouting consolidation constitutes a pivotal technical solution for addressing the issue of water-related weakening in mudstone. Given the engineering challenges such as the sub-optimal injectability of cement slurry materials into mudstone, and the deficient reinforcement strength of silica sol in the same, this study provisionally developed a composite grouting material with a multi-particle size distribution, which is suited for the closure and reinforcement of microcracks in mudstone. We characterized the fundamental solidification and grouting properties of the modified composite grouting material, and unveiled the reinforcement mechanism of aluminate cement (AC) modified silica sol. The research findings indicate that the composite grouting material exhibits a two-tiered advantageous particle size distribution at the nanometer and micrometer levels, resulting in a marked enhancement in injectability. When the quantity of AC is 50% of the silica sol mass, and the water-cement ratio of cement slurry is 0.6, the solidification time of the composite grouting material can be adjusted between 21 and 114.5 mins. The initial viscosity is less than 5 mPa·s, and the stone rate exceeds 97%. The 28-day cemented structure exhibits a volume shrinkage rate of merely 0.57%, and the compressive strength can attain 14.5 MPa. In terms of the modification mechanism, SiO2 nanoparticles effectively expedite the hydration process of AC within the composite grouting material, engendering chemical bonds in the hydration products. These fill the pre-existing pores of the cement cemented structure, thereby enhancing the mechanical strength and compactness of the internal structure of the composite grouting material cemented structure.