A novel water-swelling grouting material formulation and its performance for water rushing in karst strata

Conventional grouting materials often exhibit shortcomings when faced with water rushing in karst strata, such as easy dispersion, poor stability, and uncontrollable diffusion. This study introduces an organic-inorganic hybrid water-swelling material for grouting based on excellent synergistic interactions among Polymethylene Polyphenyl Isocyanate (PAPI), Nitrogen tetroxide (N204), Portland cement, and Triethylenediamine (A33) using a straightforward process. Meanwhile, optimal formulations for the WSGM are determined using a proposed matrix analysis model. Under specific conditions with an alcohol ester ratio of 0.9, cement content of 50 %, and catalyst content of 50 %, the resulting water-swelling grouting material (WSGM) exhibits a three-dimensional network structure, high viscosity, exceptional stability, and robust scour resistance (with an initial expansion time of 11 s, a gel time of 91 s, a volume expansion rate of 600 %, a compressive strength of 0.62 MPa, and a bonding strength of 0.39 MPa). The excellent performance of the WSGM is validated through a series of experimental tests. The potential formation mechanisms were discussed, considering the hardening process, Xray diffraction (XRD) analysis, and scanning electron microscopy (SEM) analysis. This research holds the potential to advance the development of organic-inorganic hybrid water-swelling materials with excellent performance, opening new avenues in material preparation.