Development and materials characteristics of fly ash- slag-based grout for use in sulfate-rich environments

This study improves cement–water glass two-shot grouting materials by adding fly ash and slag, making a new kind of anti-seepage grouting material for the prevention of soil contamination. The chemical corrosion mechanism and chemical resistance properties of the new grouting material were studied, and the contamination prevention performance of the anti-seepage system in complex geological environments, such as tailings ponds and heavy metal-contaminated sites, was also evaluated. The basic properties of the grouting materials, including stability and mobility, were tested. Sodium sulfate was used to corrode the grout gels after demolding, and the effects of chemical corrosion on mechanical properties were tested by unconfined compressive strength tests. The strength of the solution gels increased rather than decreased when fly ash and slag were added. The effect of chemical corrosion on grouting material composition was analyzed by X-ray diffraction. The results show that CaSO₄·2H₂O crystals have a higher diffraction peak under sodium sulfate corrosion than in standard curing conditions. This difference explains the reason for the increasing strength of the material. The effect of chemical corrosion on the gels’ microstructure was analyzed by SEM. Numbers of clubbed tri-sulfur calcium sulphoaluminate and diamond-shaped gypsum crystals were found.