Study on bond properties between near-surface mounted BFRP bars and concrete under freeze-thaw cycles in seawater

In order to explore the influence of freeze-thaw cycles on the interfacial bond durability of near-surface mounted fiber reinforced polymer (NSM-FRP) in concrete served in the high cold marine area, a pull-out test was conducted on NSM basalt fiber reinforced polymer (NSM-BFRP) bars with epoxy resin adhesive (EP) and engineered cementitious composite (ECC) material as bond materials. The interfacial failure mode and bond degradation mechanism between the NSM-BFRP bars and concrete under the freeze-thaw cycles in seawater and freshwater were analyzed. The effects of the freeze-thaw medium, cycle numbers, and bond materials on the bond properties were elucidated, and the bond-slip constitutive relationships under different conditions were determined. The results showed that the failure modes were similar in seawater and freshwater freeze-thaw conditions, and the bond strength decreased with increased freeze-thaw cycles. The reduction in seawater was slightly higher than that in freshwater. However, the effect of 50 cycles on the bond performance was relatively small. The bond-bearing capacity of the NSM-BFRP-ECC specimens was significantly lower than that of the NSM-BFRP-EP specimens; however, the former exhibited a higher ductility.