Flexural behavior of monolith and hybrid concrete beams produced through the partial replacement of coarse aggregate with PET waste

This study was conducted to compare the structural performance of monolith and hybrid reinforced concrete beams produced by partially replacing the coarse aggregates with polyethylene terephthalate (PET) shredded wastes. The process involved casting and testing a total of 6 beams with a dimension of 3300x150x250 mm under a four-point bending moment. The control specimens were cast using normal concrete and PET monolith specimens were fabricated using PET waste concrete. Moreover, the hybrid specimens were cast using normal concrete to a depth of 150 mm from the top and PET waste concrete at the remaining 100 mm depth at the bottom. The flexural behavior of the beams was then analyzed based on the load–deflection behavior, cracking behavior, failure mode, stiffness, and ductility. The test on the hardened concrete showed that the addition of the PET waste in the mixture reduced the compressive and tensile strength of the concrete. Moreover, the hybrid specimens were also observed to have better performance than PET monolith specimens. It was also discovered that the failure mode did not change in both PET waste monolith and hybrid specimens. Furthermore, the ul- timate moment capacity of the PET waste monolith and hybrid specimens was predicted using the simple analytical model for under-reinforced concrete beams and good accuracy was obtained. The findings also showed that there is a need to consider the changes in the compressive and tensile stress distribution of concrete sections for monolith PET beams in order to extend the accuracy of the analytical model.