Failure of the SRC under freeze- thaw cycles by the push-out tests

This paper explores the impact of freeze-thaw cycles, the thickness of the protective layer, embedment length, and volumetric hoop ratio on the bond performance at the SRC interface, assessed through freeze-thaw and push-out tests. Results from SEM indicated significant cracking in concrete exposed to freeze-thaw cycles, with an increase in both the number and diameter of pores. Despite significant damage to the concrete exterior, the interface exhibited considerably less deterioration. Following 200 freeze-thaw cycles, the specimens displayed a maximum crack depth of 2.3 mm and a porosity rate of 35.1 %. As the cycles progressed, the failure mode of specimens under push-out loading transitioned from splitting to interfacial shear failure. Notably, the length of cracks on the end surfaces was markedly reduced, and the majority of specimens exhibited minimal cracking on the side surfaces. Additionally, interfacial bond stress decreased progressively with the increasing number of cycles. The ultimate bond stress declined more rapidly than residual bond stress, with the rate of decrease stabilizing after surpassing 100 cycles. Enhancements in protective layer thickness, embedment length, and volumetric hoop ratio effectively mitigated the reductions in bond stress. Among these, the protective layer had the most significant impact, followed by the volumetric hoop ratio, while embedment length had the least influence. The study concludes with proposed formulas for calculating bond stress and slip eigenvalues after freeze-thaw cycles, integrating experimental results and theoretical analysis.