Synthesis and Multi-Scale Performance Analysis of Water-Insensitive Polyurethane Grouting Materials

The performance reliability of polyurethane grouting materials is frequently undermined by pronounced moisture sensitivity, particularly under humid and freezing-thaw exposure. To address this limitation, a compositionally adaptive strategy incorporating azolyl-type latent curing agents was developed to enhance microstructural integrity and mechanical retention in water-sensitive environments. A gradient-based formulation design, implemented under high-humidity conditions (RH ≈ 95%), facilitated a systematic investigation into the evolution of foaming behavior, chemical crosslinking, and mechanical performance across tensile, compressive, and freezing-thaw domains. The incorporation of latent curing agents was found to attenuate water-induced side reactions, promoting the formation of urea linkages and an expanded N-H hydrogen bonding network—thereby driving the transformation of cellular morphology toward a more compact and structurally coherent architecture. At a 2% dosage, the formulation exhibited an optimal balance across multiple mechanical dimensions, achieving simultaneous gains in strength, stiffness, ductility, and durability. By contrast, further increases in curing agent concentration led to excessive crosslinking, which induced local rigidity and diminished strain adaptability, ultimately compromising damage tolerance. These observations culminate in the establishment of a structure-reaction-performance coupling framework that affords predictive control over foam behavior under coupled hygrothermal stresses. The resulting design paradigm provides both mechanistic insight and practical guidance for the development of polyurethane grouting systems with enhanced resilience in humid-cold composite environments.