Study on the basic performance and feasibility of Sulfoaluminate–Potassium magnesium phosphate dual-liquid grouting materials under high water–cement ratio conditions

This study investigates a novel dual-liquid grouting material composed of sulfoaluminate cement (CSA) and magnesium potassium phosphate cement (MKPC), designed for dynamic water sealing under high water–cement ratio conditions. Material A (MgO, anhydrite, and CaO) and Material B (CSA and KH₂PO₄) were mixed at a fixed water–cement ratio of 1.3. By optimizing the CSA:CS:CaO ratio, the Mg/P molar ratio, and the MKPC content, the system achieved an excellent balance between ultra-rapid setting (15–75 s) and high long-term compressive strength (up to 5.3 MPa at 28 days). Microstructural analyses (DTA-TG, XRD, SEM) revealed the hydration mechanism: needle-like AFt crystals from CSA and plate-like K-struvite from MKPC interlock to form a dense network, which is responsible for the enhanced performance. However, an excessive MKPC content disrupts this network, leading to a coarse microstructure and strength reduction. This synergistic approach overcomes the limitations of single-system grouts, providing an efficient and feasible solution for sealing water inflows in karst pipelines under high water pressure.