Development and Application of Flue Gas Desulfurized Gypsum and Blast-Furnace-Slag-Based Grouting Material for Cracked Silty Mudstone

The grouting technique is an efficient method for enhancing the stability of cracked slopes through the use of grouting materials. Conventional cement-based grouting materials are costly, energy-intensive, and environmentally damaging. Additionally, cement-hardening slurry is prone to cracks between the slurry and the rock. To address these issues, this study proposed an environmentally friendly grouting material composed of flue gas desulfurization gypsum (FGDG) and blast furnace slag (BFS) with sodium gluconate (SG) as the additive, especially designed for cracked silty mudstone slopes. The effects of different FGDG-to-BFS ratios and SG dosages on the setting time, fluidity, shrinkage, unconfined compressive strength (UCS), tensile strength, and shear strength parameters of hardened grouting slurries, as well as the interfacial bonding strength between silty mudstone and the hardened slurries, were investigated through laboratory tests. Subsequently, the improvement effects of cement-based material and the FGDG-BFS material on cracked silty mudstone were compared by mechanical tests. Finally, the performance of both types of grouting material on cracked silty mudstone slopes was analyzed by numerical simulations based on GDEM. The results demonstrated that the optimal FGDG-to-BFS ratio was 0.8:1, under which, the mechanical properties of the hardened FGDG-BFS slurries cured for 14 days exceeded those of the silty mudstone. The optimal dosage of SG was 0.4%, effectively prolonging the setting time of the slurry and improving the water resistance of the hardened slurries. The FGDG-BFS material exhibited a superior performance in repairing rock cracks compared to cement-based materials, with the damage patterns of the grouted specimens aligning with those of the intact specimens. This new grouting material effectively repaired existing cracks and prevented re-cracking at the interface between the grouting material and silty mudstone, thereby maintaining slope stability over a long period.