Bonding Properties of Different Kinds of FRP Bars and Steel Bars with All-Coral Aggregate Seawater Concrete

AbstractAll-coral aggregate seawater concrete and fiber-reinforced polymer (FRP) can overcome the shortcomings of conventional steel and concrete. This paper evaluates the bonding performance of different kinds of FRP bars and rebar with all-coral aggregate seawater concrete by using pullout tests. The results showed that specimens with plain round bars, deformed carbon fiber–reinforced polymer (CFRP) bars, and rebar mainly experienced pullout failure, while specimens with deformed basalt fiber–reinforced polymer (BFRP) bars and glass fiber–reinforced polymer (GFRP) bars experienced splitting failure. Different rib heights, rib spacings, and rib inclination angles caused different failure modes. The effects of fiber type, surface condition, failure mode, and concrete type on the bond behavior were analyzed. It was found that, owing to a difference in surface roughness, the ultimate load of plain round CFRP bars with coral concrete was weaker than those of plain round GFRP bars and BFRP bars. The ultimate load of plain round BFRP bars with coral concrete was more than five times that of ordinary concrete with the same designed cube compressive strength, mainly because coral reef sand had a large water absorption rate and the actual water/cement ratio was relatively low, which led to an increased cement mortar strength. When the concrete strength was high, adhering sand to the surface of the FRP bars resulted in a small increase in the ultimate load. The ultimate load of ribbed steel bars with coral concrete was similar to that of deformed BFRP bars with coral concrete, but the bond failure mechanism was different. Compared with the influence of the type of FRP bar on the bonding performance, the influence of the rib parameters was greater.