Impact Behavior of Fiber-Reinforced Concrete with Polypropylene Fibers and Carbon Fiber–Reinforced Polymers

As discussed in the earlier paragraphs, both fibers and FRPs can improve the impact resistance of RC structures. However, there are not enough experimental and numerical studies focusing on the effects of both PP fibers and CFRPs on the impact behavior of different types of RC specimens. Then, it is necessary to fill this gap more and study the interaction of fibers and FRPs with each other to improve the impact resistance of RC specimens. The goals of this study are to find a more appropriate strategy (using fibers, CFRPs, or both of them) and optimum fiber content ratios to improve the impact resistance of RC members. In this study, bidirectional CFRP confinement along with PP fibers was used to investigate their effects on the impact resistance of concrete samples. Forty-nine concrete cylindrical samples (150 × 300 mm2) with the fibers (with the ratios of 0 %, 1 %, 1.5 %, and 2 %) were tested at the age of 28 days. The compressive strengths of concrete samples were 20, 30, and 40 MPa at 28 days. Besides, half of the samples were tested with the CFRP confinement (wrapping), and the other half were tested without the confinement. This dropping cycle continued until at least 30 % of the sample weight was reduced and the samples were destroyed. The results indicated that the concrete without fibers and FRPs (with the compressive strengths of 20, 30, and 40 MPa) did not have sufficient impact resistance and were quickly destructed. However, as the content ratios of the PP fibers increased, the number of cracks and the weight droppings to reach 70 % of the initial sample weight increased, too. Moreover, it was observed that concrete samples wrapped with CFRP sheets also withstood impact loading better than FRCs and were destructed with the greater numbers of droppings. It was also shown that the prevailing failure mode of the samples with FRPs was FRP layer rupturing or debonding. Finally, it was observed that the more the compressive strengths of concrete, the more the impact resistance.