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 bondbearing 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.