Durability Improvement and Microscopic Damage Mechanism of Waterborne Epoxy Modified Cement Grouting Materials Under Corrosion

Cement-based grouting materials may suffer strength loss and impermeability degradation when exposed to oil- and gas-bearing corrosive environments. In this study, 7.0% waterborne epoxy resin was used as a polymer admixture to improve the durability of cement-based grout under coupled corrosive exposure. Actual corrosive fluid from an engineering site and accelerated dry–wet cycling were used to simulate the service environment. The evolution of mechanical properties, impermeability, and dominant microstructural damage was then examined. The results show that the unmodified grout deteriorated markedly during cyclic exposure. After 120 cycles, its compressive strength decreased from 37.4 MPa to 26.2 MPa, the elastic modulus decreased by 44.1%, and the impermeability pressure dropped from 0.9 MPa to 0.3 MPa. By contrast, the grout containing 7.0% waterborne epoxy resin showed better durability. The strength and modulus losses were limited to 17.4% and 21.0%, respectively, and the impermeability pressure remained at 0.6 MPa, about twice that of the unmodified grout. Microscopic results indicate that dry–wet alternation promoted aggressive ingress and crack growth. The epoxy phase formed a relatively continuous film in the matrix, reduced penetration pathways, and slowed internal damage development. Based on the observed damage evolution, a mechanical prediction model and a new impermeability grading method were established. These findings show the potential of polymer admixture modification for improving the long-term performance of cement-based grouting materials in aggressive environments.