Shear behavior of reinforced concrete beams with gfrp needles as coarse aggregate partial replacement: Full-scale experiments

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 discrete reinforcements (referred to as “needles” hereafter) as coarse aggregate in concrete has been suggested as a possible solution to FRP waste recycling. It has previously been observed in small specimens that FRP needles increase the tensile strength and energy absorption capacity of concrete. This paper presents an experimental investigation into the effect of GFRP needles as coarse aggregate partial replacement in concrete on shear behavior of full-scale reinforced concrete (RC) beams. A total of 10 RC beams without steel stirrups in the critical zone were tested under four-point bending. The volume replacement ratio of the coarse aggregate and the surface type of GFRP needles were chosen as the test parameters. GFRP needles, with either smooth or helically wrapped surfaces, were added to the concrete mix to replace 5% or 10% of coarse aggregate by volume, respectively. All test beams failed in shear in a brittle manner with the 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 reduction in the load carrying capacity.