Shear behavior of reinforced concrete beams with GFRP needles

Fiber-reinforced polymer (FRP) waste is becoming an environmental concern due to the widespread use and non-biodegradable nature of FRP composites. Cutting FRP waste into short-length randomly distributed reinforcing bars (referred to as “needles” hereafter) as a substitute for part of the coarse aggregate in concrete has been suggested as a possible solution to FRP waste recycling. This paper presents to the authors’ best knowledge the first reported experimental investigation into the effect of GFRP needles as coarse aggregate partial replacement in concrete on the shear behavior of large-scale reinforced concrete (RC) beams. A total of 10 RC beams without steel stirrups in the critical half were tested under four-point bending. The volume replacement ratio of coarse aggregate and the surface type of GFRP needles were chosen as the test parameters. All test beams failed in shear in a brittle manner with their ductility being slightly enhanced by the partial replacement of coarse aggregate using GFRP needles. An enhancement of 8–10% in the load-carrying capacity was observed in beams with helically wrapped needles, while beams with smooth needles showed a slight reduction in the load-carrying capacity. The presence of GFRP needles increased the amount of total energy absorbed by the RC beams by about 33–40%.