Freeze-thaw damage inhomogeneous effect on corrosion cracking behaviour of reinforced concrete

Purpose The freeze-thaw damage shows an obvious gradient effect with the depth, the accumulated damage leads to an inhomogeneous degradation of the concrete mechanical properties. This study aims to investigate the influence of the freeze-thaw damage gradient on the corrosion-induced cracking behavior of the concrete cover through experimental and theoretical analysis. Design/methodology/approach Reinforced concrete prism specimens with different cover thicknesses (20, 25, 30, 35, 40 mm) were designed and fabricated, and accelerated corrosion tests were conducted on specimens subjected to different freeze-thaw cycles (FTC) (0, 50, 100, 150, 200 cycles). The gradient strain fields on the concrete surface were monitored by the DIC technique. Concrete ultrasonic velocity along the depth was tested layer-by-layer at intervals of 2 mm. Findings The test results showed that critical corrosion ratio of reinforcing bars decreased as the cover thickness increased under different FTC. The splitting tensile strength and the relative dynamic modulus of damaged concrete showed bilinear degradation with depth, and also freeze-thaw damaged evolution equations along the depth were proposed. Considering the impact of freeze-thaw damaged gradient, a concrete cover corrosion cracking model was established, and the theoretical values agreed well with the test results. Originality/value The research findings can provide a basis for the durability assessment of reinforced concrete structures in cold regions. The proposed model can predict the critical corrosion ratio of reinforcement under freeze-thaw environments.