Investigating the effect of different types of fibers in improving the flexural performance of recycled concrete beams in the elastic and plastic zones

This paper presents the results of an experimental investigation on the flexural performance of concrete beams containing recycled aggregates concrete (RCA) and reinforced with a variety of fibers. In this research, 5 concrete beams with a length of 150, width 20 and height 30 cm were made. One beam containing natural aggregate (NA) and fiber-free as control specimen, one beam containing RCA and fiber-free and the other three beams containing RCA and reinforced with 0.5% of each of the steel, polypropylene and korrta fibers. The performance of the beams were investigated under four-point bending test in two elastic and plastic zones. The parameters of limit of proportionality, modulus of resilience, flexural modulus of elasticity and yield moment in the elastic zone and the parameters of the ultimate moment, ductility, energy absorption and flexural toughness in the plastic zone were investigated. Beams containing NA and RCA had a slight difference (less than 10%) in all the mentioned parameters. On the other hand, the fibers used improved the flexural performance of the recycled beams in both elastic and plastic zones, which the effect of steel fiber was more significant than polypropylene and korrta fibers. Finally, the experimental results obtained in this study were compared with the results of Iranian Concrete Code (ABA), ACI 318, EuroCode 2 and CSA. The results of this comparison indicated that the lowest difference with the experimental results is related to ACI 318 and the highest difference is related to EuroCode 2.