Mechanical Properties and Damage Mechanism of Underwater Nondispersible Polymer under Freeze–Thaw Conditions

Grouting repair techniques are widely used in civil engineering but encounter challenges in water-rich environments and freeze–thaw conditions in cold regions. This study presented a novel underwater nondispersible polymer grouting material designed for such environments. The mechanical degradation of the underwater nondispersible polymer during freeze–thaw cycles in wet-frozen and water-immersion-frozen conditions was investigated using uniaxial compression tests. The impact of freeze–thaw cycles on the material was most significant in the early stages. After five freeze–thaw cycles, the unconfined compressive strength and peak strain stabilized, retaining over 90% of the original strength (from 31.47 to 28.47 MPa) and more than 92% of its toughness (from 0.39 to 0.36). The strength and toughness of water-immersion-frozen specimens were comparable to those of the wet-frozen group, highlighting the material’s potential applicability in cold, water-rich environments. Acoustic emission activity increased with the number of freeze–thaw cycles. A Gaussian mixture model was used to cluster and analyze acoustic emission parameters. It was observed that, in the wet-frozen group, tensile cracks decreased from 84.5% to 46.6%, while shear cracks increased from 15.5% to 53.4% as freeze–thaw cycles progressed. The corresponding rates were notably slower in the water-immersion-frozen group compared to those in the wet-frozen group. Scanning electron microscopy analysis further indicated better material integrity and less structural damage in the water-immersion-frozen specimens compared to the wet-frozen group subjected to the same number of freeze–thaw cycles. This study demonstrates the potential applicability of this new polymer grouting material in cold, water-rich environments.