The influence of waste polypropylene fibers on the behavior of sustainable reinforced concrete beams

Abstract

Plastic waste has recently become one of the most important environmental issues. Plastic fibers in concrete provide a long-term solution to plastic waste management. Concrete is a rigid material and has superior compressive strength but has poor tensile strength. Using waste plastic fibers in concrete can address its brittleness and low tensile strength. In this study, waste polypropylene fiber (WPF) prepared from discarded plastic tapes in reinforced concrete (RC) beams was used. WPF of 5 mm width was added to the concrete at a volumetric percentage of 1%. The fibers were added at different lengths (50, 70, and 90 mm) individually, and then all lengths were mixed randomly. This study provides the results of laboratory tests conducted to evaluate the mechanical properties of the WPF-RC. Additionally, a comparison of RC beams with the same percentage of reinforcement but varying lengths of WPF in the tensile zone was provided. The criteria for the flexural test were determining the ultimate load, the yield, and the first cracking as well as the deflections associated with these loads. Evaluations of the energy absorption index, ductility, and failure modes were also carried out. The WPF enhanced the ultimate load by 5%, the deflection at the ultimate load by 33.26%, and the splitting tensile strength by 51.47% for the concrete. Additionally, the load– deflection relationships demonstrated that concrete beams reinforced with WPF tend to deflect more before failing. The energy absorption index capacity is increased by 94.36% and ductility by 25.83% for the beam reinforced with 1% WPF, mixed randomly at mixing randomly lengths. This possible enhancement of RC beam performance based on the WPF can promote the use of sustainable concrete in many structural applications based on the WPF.