Bond durability of basalt fiber-reinforced polymer bars embedded in concrete under direct pullout conditions

The use of basalt fiber-reinforced polymer (BFRP) bars as a reinforcing material has gained increasing interest worldwide. However, few studies have reported on these bars' performance in concrete when exposed to harsh environments. This paper investigates the effect of five different accelerated environments, namely (1) tap water, (2) seawater, (3) elevated temperature, (4) elevated temperature followed by tap water, and (5) elevated temperature followed by seawater, on the bond stress-slip response, adhesion to concrete, and bond strength [of two types of BFRP bars and one type of glass fiber-reinforced polymer (GFRP) bar]. The bond-slip responses of all specimens were governed by the surface treatment of each bar and its manufacturing quality, regardless of the fiber type. Sand-coated BFRP bars showed higher bond characteristics than helically grooved bars after conditioning. Moister environments caused enhanced adhesion at the early loading stages for all specimens. Nevertheless, such environments had a detrimental effect on the bond strength at later stages depending on the bar material's moisture absorption. Finally, exposure to elevated temperatures caused insignificant variation in the bond strength of all tested specimens.