Influence of Early Dry-Wet Cycles on Performance and Durability of Steel-Fiber Recycled Coarse Aggregate Concrete

To enhance the durability of recycled coarse aggregate concrete (RCAC) under early dry-wet cycles, this study investigates the effects of incorporating copper-plated steel fibers (CPSFs) at volume fractions of 0%, 0.5%, 1.0%, and 1.5%. We systematically evaluated the Cl^- erosion resistance, splitting tensile strength, mass-change rate, pore structure, phase composition, and microstructural evolution of RCAC subjected to 21 NaCl dry-wet cycles. Results show that CPSF effectively inhibits microcrack propagation and improves the interfacial transition zone within the concrete matrix. At a fiber content of 1.5%, the mass of the specimen increased by 1.23% after 21 erosion cycles, and the splitting tensile strength reached 2.86 MPa, which is 80% higher than that of the fiber-free control group. Comprehensive evaluation using the entropy weight method confirms that RCAC with 1.5% CPSF exhibits the best durability performance. This study demonstrates that an appropriate dosage of CPSF significantly mitigates the detrimental effects of early dry-wet cycles on RCAC performance.