The Evolution of Concrete Expansion Deformation under Wet-Dry Cycles and Composite Salt Corrosion

Abstract This study investigates the expansion and deformation characteristics of concrete with varying strengths under the conditions of aqueous solution, wet-dry cycles, and complex salt corrosion environments. The experimental results indicate that under the action of wet-dry cycles, the expansion rate of C30 and C50 concrete specimens in the aqueous solution increases with time, but the overall degree of deformation is relatively small. Due to its higher water-cement ratio, the expansion rate of C30 concrete is generally greater than that of C50 concrete. In a 3% sodium sulfate solution, the expansion rate of C50 concrete is lower than that of C30, which is related to its lower water-binder ratio and denser microstructure. In a 5% sodium sulfate solution, the expansion rate of C30 concrete is significantly higher than that of C50, demonstrating a faster rate of expansion. In the environment of mixed sodium sulfate and sodium chloride solution, the presence of chloride ions effectively mitigates sulfate erosion, reducing the expansion rate. Furthermore, with the increase in sulfate concentration, the expansion and deformation of concrete increase. The expansion and deformation of C50 concrete in sodium sulfate solution are less than that of C30, which is related to its higher tensile strength. The research provides a scientific basis for the durability assessment and protection of concrete structures in sulfate erosion environments.