Behavior of unconfined and polyethylene terephthalate (PET) FRP-confined coal reject concrete under compression

Abstract

Fiber-reinforced polymer (FRP) confinement has been proposed to mitigate the detrimental effects of coal rejects concrete (CRC) in the present study. Polyethylene terephthalate (PET) FRP jacket was adopted to confine CRC as a new type of novel column members, which are referred to as PET FRP-confined coal reject columns (PFCCRs). PFCCRs are often sustainable and cost-effective structural columns as the PET FRP composites are generally made from recyclable PET waste and coal rejects are industry by-products. A total of 49 columnar specimens, consisting of 21 CRC specimens and 28 PFCCR specimens were tested under uni-axial compression to understand the mechanical behavior of unconfined and PET FRP-confined CRC. The main parameters evaluated in this study were the volume replacement ratio of coal rejects and the FRP thickness. The test results indicated that the unconfined CRC specimens exhibited a significant reduction in compressive strength with the increase in replacement ratio, whereas the ultimate axial strain was enhanced. Compared with plain CRC specimens, PFCCRs had excellent deformation capacity and compressive strength with a strain hardening stress-strain response. The maximum normalized ultimate axial strain and axial stress of most of the PFCCR specimens are over 30 and 7, respectively. The stress reduction segment will occur only when the FRP confinement is insufficient. Furthermore, the test results were compared with the predictions by using existing analysis-oriented and design-oriented models for LRS FRP-confined concrete to verify their accuracy.