Structural Behavior of Waste Plastic Concrete Beams Reinforced by Fiber Reinforced Polymer

Abstract

This study submits the systematic experimental program to explore the effect of incorporating the waste plastic fiber as polyethylene terephthalate (PET) on the mechanical properties (fresh and hardened) of the normal concrete and the shear behavior of the reinforced concrete beams. This study also applied the concept of sustainability by using cumulative waste plastic in the environment such as soft drink bottles. The soft drink bottles were cut to the laminate fibers with the specific dimensions and mix it with the concrete mixture, thus will reduce the environmental pollution. The experimental program of this study focuses on the comparison between the shear structural behavior of the reinforced concrete beams, there are three parameters (I) difference fiber percentages (0%, 0.5%, 1%, 1.5%), (II) different types of stirrups (e.g. steel and carbon fiber reinforced polymer CFRP), and (III) difference width of CFRP stirrups (e.g. 6mm, 12mm, and 18mm). All beams were reinforced in longitudinal direction with three GFRP bars at the bottom and two steel bars at the top. The mechanical properties (fresh and hardened) were evaluated using the slump test, compressive strength test, splitting strength test, elastic modulus test, flexural toughness test, density test, and ultrasonic test. The structural behavior was evaluated by testing the beams under the four points load. The mechanical properties of the normal concrete were improved by adding the PET fibers. The workability of the normal concrete was reduced by 75% at the fiber percentage 1.5%. Compressive and tensile strength were increased by 5% and 18.8% at the fiber percentage 0.5% and 1%, respectively while, the elastic modulus was decreased by 17% at the fiber percentage 1.5% compared with the reference mix. In addition, there was a significant improvement in toughness index about 9.3%, 27.11%, and 21.22% at the fiber percentage 0.5%, 1%, and 1.5%, respectively compared with the reference mix. The modulus of rupture increased by 4% at the fiber percentage 0.5% and then decreased by 9.3% and 12.9% at the fiber percentage 1% and 1.5%, respectively compared with the reference mix. III For the shear structural behavior, the beams divided into four groups (A, B, C, D). Group (A) included four beams with steel stirrups and different fiber percentage 0%, 0.5%, 1%, and 1.5%. Group (B) included four beams with CFRP stirrups (width 6mm) and different fiber percentage 0%, 0.5%, 1%, and 1.5%. Group (C) included four beams with CFRP stirrups (width 12mm) and different fiber percentage 0%, 0.5%, 1%, and 1.5%. Group (D) included four beams with CFRP stirrups (width 18mm) and different fiber percentage 0%, 0.5%, 1%, and 1.5%. It is found that the PET fiber improvement the structural behavior in terms of toughness, ductility, and failure mode. The results indicated that the effect of the PET fibers in beams with CFRP stirrups was more than the beams with steel stirrups. In light of this point, it was concluded that the low elastic modulus for CFRP enhanced the role of the PET fibers in improving the structural behavior of the reinforced beams. The results also showed that the PET fiber improving the shear ductility of the reinforced concrete beams for all groups.