A Novel Silane Modification Strategy for Enhancing Crack Resistance and Toughness in Steel Fiber Reinforced Concrete Under Chloride Erosion: Insights from XTDIC Digital Speckle Analysis

To improve the corrosion resistance of steel fibers under chloride ion attack in coastal environments and enhance the interfacial bonding between steel fibers and concrete, this study utilized an optimized concentration of γ-aminopropyltriethoxysilane (KH550) solution. Through a hydrolysis–condensation reaction, a silane modification protective film was formed on the surface of the steel fibers, leading to the development of a novel anti-corrosive steel fiber reinforced concrete. Semi-cylindrical specimens of both silane-modified and ordinary steel fiber reinforced concrete were prepared. After subjecting these specimens to dry–wet cycles in a chloride salt environment, they were mechanically loaded using a UTM testing machine, and the loading process was monitored using the XTDIC digital speckle technique. Microstructural characterization confirmed that KH550, via hydrolysis–condensation reactions, effectively generated a modification film on the surface of the steel fibers that prevented chloride ions from penetrating and reduced chloride-induced corrosion. Mechanical tests show that the peak load of the modified specimens increased by 4.24%, and the time required for destruction in the stress concentration stage, crack initiation stage, and macro-crack development stage was prolonged and the strain rate was reduced, proving that the interface bonding ability was enhanced. Overall, this technology achieves a synergistic optimization of durability and mechanical performance through an interfacial reinforcement strategy, providing a new approach for protecting coastal engineering structures against chloride-induced corrosion.