Bond durability between GFRP rebars and fiber reinforced self-compacting concrete under coupled chloride salt and freeze-thaw cycles

To investigate the influence of various fibers on the bond performance between Glass Fiber Reinforced Polymer (GFRP) bars and concrete under the combined effects of chloride salt and freeze-thaw cycles, pull-out tests were conducted on 90 specimens. The main variables were the number of freeze-thaw cycles, fiber types, and fiber content. The results demonstrate that the addition of polypropylene short fibers (PPFA) enhances the frost resistance of concrete and mitigated bond strength degradation between steel fiber-reinforced concrete and GFRP bars under chloride salt-freeze-thaw conditions. When added individually, both polypropylene long fibers (PPFB) and steel fibers (SF) significantly improve the bond strength between GFRP bars and concrete after exposure to chloride salt-freeze-thaw cycles. The combination of 40 kg/m³ SF and 2 kg/m³ PPFB results in the most notable improvements in the mechanical properties of concrete. Compared to specimens without fibers, the inclusion of fibers increases the bond strength between concrete and GFRP bars by 39.4% after exposure to chloride salt and freeze-thaw cycles. Based on the experimental results in the present study, the ascending branch is established accounting for the effects of chloride salt and freeze-thaw cycles, and the predicted model corresponds well with the testing curve.