Bond between Sand-coated GFRP Bars and Normal-strength, Self-compacting, and Fiber-reinforced Concrete under Seawater and Alkaline Solution

Bond durability between fiber-reinforced polymer (FRP) bars and concrete is a significant point of concern with respect to structural integrity, performance, and retrofit purposes. This experimental study addresses the bond durability of glass-FRP (GFRP) bars embedded in different concretes after exposure to harsh environmental conditions (i.e., seawater and an alkaline solution at 60° C). A total of 54 beam specimens of self-compacting, fiber-reinforced, and normal concretes were constructed, conditioned, and tested under flexural pullout according to RILEM provisions, which simulate the reinforcement behavior as a structural element in buildings. Sand-coated GFRP bars and steel bars were used to reinforce concrete beams. The obtained results demonstrated that the bond strength of beams with sand-coated GFRP bars decreased less after exposure to seawater in comparison with alkaline solution. However, the converse outcome was found for beams with steel bars. In addition to the reinforcing bars, the type of concrete was found to be effective in the bond durability of beams with both GFRP and steel bars under aggressive environments. Generally, the higher the density and strength, and the lower the permeability, the greater the bond strength and less its reduction.