Influence of Steel and Polypropylene Fibers on Flexural Behavior of RC Beams

Abstract

Seven full-scale concrete beam specimens are tested under gradually increasing monotonic loading to investigate their overall flexural response due to the addition of both metallic and nonmetallic fibers to the concrete. Steel and polypropylene fibers of 0.5% and 1.0% volume fraction are used in the fiber-reinforced concrete (FRC) beam specimens. No improvement is noticed in the compressive and splitting tensile strengths of concrete due to the addition of polypropylene fibers only. However, an improvement of 25–100% in the concrete splitting tensile strength is noticed when either steel or combined fibers are added to the concrete. Although an increase in fiber content in the combined FRC improves various mechanical properties, its influence on the peak load-resisting capacity of the full-scale beam specimens is rather limited. An increase of both steel and polypropylene fibers in excess of 0.5% volume fraction does not improve the ultimate flexural resistance of beams due to the uneven distribution of similar sizes of fibers in the presence of reinforcing steel bars. However, displacement ductility of the beam specimens is improved by 120% as compared with the RC specimen, when only polypropylene fibers of 1% volume fraction are added to the concrete. A better postpeak residual strength response is noticed in case of all FRC beam specimens due to multiple cracking associated with the fiber-bridging action.