Axial Compressive Behavior of SRC Columns After Freeze-Thaw Cycles

This study investigates the impact of freeze-thaw cycles on the axial compressive behavior of steel-reinforced concrete (SRC) columns. Axial compression tests were conducted on twenty-eight SRC columns subjected to freeze-thaw cycles. Key parameters included the number of freeze-thaw cycles, freezing medium, compressive strength of concrete, and volumetric stirrup ratio. The study examined the degradation in ultimate load-bearing capacity, failure mechanisms, and performance indicators using Digital Image Correlation (DIC) to capture failure processes under axial loading. Three failure modes were identified: localized cracking, multi-crack development, and delamination of the outer protective concrete layer. These failure modes were found to be influenced by both the number of freeze-thaw cycles and the compressive strength of the concrete. Significant reductions in both ultimate load and stiffness were observed, with maximum decreases of 30.33 % and 75.82 % under freshwater conditions, and 36.75 % and 78.07 % under seawater conditions, respectively. Although ductility generally declined after freeze-thaw cycles, some specimens showed increased ductility due to altered failure modes. After 50 freeze-thaw cycles, the difference in performance degradation between freshwater and seawater conditions was negligible. However, once the number of cycles reached 100, the reduction in both ultimate load and stiffness caused by seawater exposure became significantly more severe than that caused by freshwater. Based on the experimental findings and theoretical analysis, a predictive method was developed to estimate the ultimate axial capacity of SRC columns after freeze-thaw cycles, achieving a prediction error within 10 %.