Durability and erosion of electrolytic manganese residues modified by low-temperature thermal treatment for karst grouting materials

The durability of karst grouting materials in real-world environments is critical for the sustainable application of engineering projects. This study investigates the use of low-temperature thermally modified electrolytic manganese residue (EMR) as a composite activator (CA) in synergy with ground granulated blast-furnace slag (GGBS) to produce EMR-GGBS cement (EGC) for karst grouting materials. The aim is to evaluate its durability and erosion mechanisms. To simulate actual environmental conditions (water, EMR leachate, and acid rain), wet-dry cyclic tests were conducted, assessing parameters such as density, permeability, and unconfined compressive strength (UCS). A strength evolution law and a cyclic response model for the EGC solidified body were developed, and the corresponding model parameters were determined. Furthermore, XRD, SEM-EDS, MICP, and toxicity tests were employed to comprehensively analyze the structural and environmental effects of erosion. The results show that the addition of CA significantly enhances the material's corrosion resistance, particularly in resisting EMR leachate. It was found that pore damage and the carbonation decomposition of ettringite (AFt) are the primary causes of reduced durability. Furthermore, during wet-dry cycles in EMR leachate, MnO(OH) 2 precipitates forming on the surface of the solidified body were found to mitigate ion erosion. As the pH increases, the release of Mn 2+ and NH 3 -N decreases due to precipitation and the volatilization of ammonia. This study deepens the understanding of the durability and anti-corrosion mechanisms of EGC grouting materials, providing theoretical guidance for the long-term performance evaluation of grouting and sealing in karst regions.