Corrosion Inhibition in Concrete: Synergistic Performance of Hybrid Steel-Polypropylene Fiber Reinforcement Against Marine Salt Spray

In the marine salt spray environment, steel fiber reinforced concrete (SFRC) structures are often subjected to accelerated durability degradation, primarily due to chloride-induced corrosion. To address this issue, polypropylene (PP) fibers were incorporated to partially replace steel fibers in the formulation of hybrid fiber reinforced concrete (HFRC), thereby enhancing its resistance to chloride corrosion. The results demonstrate that all HFRC mixtures achieved a compressive strength of approximately 65 MPa at 28 d. After 200 d of salt spray exposure, the compressive strength of the HFRC containing PP fibers decreased at a significantly slower rate than that of the control group (M0) incorporating sole steel fibers, with the former still meeting the high-strength concrete standard (>60 MPa). Regardless of the exposure duration to salt spray, the wave velocity of the HF series remained higher than that of M0. This suggests that the PP fibers play a significant role in preserving the matrix’s compactness, effectively mitigating deterioration caused by chloride corrosion. Furthermore, after 200 d of exposure, the peak chloride content, critical corrosion depth, and chloride diffusion coefficient of HF2 were 0.58%, 16 mm, and 1.24 × 10−12 m2/s, respectively, all of which were lower than those of the other specimens. This demonstrates that incorporating 0.3 vol% PP fibers most effectively enhances the chloride corrosion resistance of HFRC.