Effects of epoxy resin pre-curing in low-temperature environments on the repair performance of wet cracks in concrete

Cracking in hydraulic concrete is often accompanied by water leakage, and crack grouting repairs are typically performed during low-temperature seasons. To investigate the effect of epoxy resin pre-curing under prolonged grouting conditions in low-temperature environments on the repair efficiency of wet cracks, a low-temperature pre-reaction method was used to simulate the curing process of epoxy resin in a grouting container. The effects of pre-curing on slurry properties, cured material properties, repaired concrete performance, and microstructure were studied. Results indicate that after low-temperature pre-curing, the exothermic temperature rise of the slurry decreased by 38.0%, and the shrinkage rate of the cured material reduced by 12.0%. Additionally, the compressive and tensile strengths of the cured material increased by 2.8% and 8.9%, respectively. For repaired concrete, the wet bond strength and splitting tensile strength improved by up to 34.3% and 46.9%, respectively, with failure modes shifting from crack surface fractures to substrate fractures. Compressive strength recovery reached 100%. Scanning electron microscopy revealed that the microdefects in the cured epoxy resin were significantly reduced, and the density and uniformity were markedly enhanced. Therefore, in low-temperature environments, lowering the grouting rate and extending the grouting duration can effectively improve the repair performance of wet cracks in concrete.