Multi-Scale Degradation Behavior and Durability of BF-WEP Modified Concrete Under Saline Environments

To improve the durability of concrete in the saline environment of southern Xinjiang, concrete was modified with basalt fiber (BF) and waterborne epoxy (WEP). A one-year outdoor natural-exposure test in Aksu, Xinjiang, systematically investigated the corrosion resistance and multi-scale deterioration behavior and durability of the modified concrete. Compared with C0, the BF2E2 mixture reduced the mass loss rate and flexural strength loss rate by 54.65% and 37.20%, respectively, while increasing the relative dynamic elastic modulus by 14.55%. The modified mixtures also showed decreased total porosity, reduced average pore area, and narrowed crack widths, with significantly attenuated diffraction peaks of corrosion products. Threshold-crossing times obtained by extrapolation indicated that the earliest threshold-crossing time of BF2E2 was extended by 62.14% compared with C0, with the relative dynamic elastic modulus serving as the governing durability criterion. Mechanistic analysis revealed that BF and WEP acted collaboratively through fiber bridging and polymer filling, forming a dual-reinforcement network that suppressed deterioration from the microstructural to the macroscopic scale. These findings provide guidance for the durability-oriented design of concrete structures in saline environments.