Compressive behavior of FRP-confined normal concrete or seawater sea-sand concrete containing FRP-bar recycled coarse aggregates

Fiber-reinforced polymer (FRP) waste has become an environmental concern owing to the non-biodegradable nature and widespread use of FRP composites. Cutting the disposed waste of FRP bars into small pieces (referred to as FRP-bar recycled aggregate or FRP-RA) and replacing natural coarse aggregate in concrete with these pieces is considered a promising solution for recycling FRP waste. Owing to its excellent corrosion resistance, FRP-RA can be used as a raw material for the production of seawater sea-sand concrete (SSC). This study investigated the axial compressive behavior of FRP-confined normal concrete (NC) or SSC containing FRP-RA. The FRP-RA was cut from glass FRP (GFRP) bars of different diameters. Axial compression tests were conducted on 96 specimens. The specimens were designed with the following parameters: the type of concrete (NC and SSC), natural coarse aggregate replacement ratio (0%, 33%, 66%, and 100% by volume), thickness (1-layer and 2-layer), and type (carbon FRP and GFRP) of the FRP jacket. The test results indicated that the presence of the FRP-RA reduced the compressive strength and elastic modulus of the concrete. FRP confinement significantly enhanced the compressive strength and ultimate axial strain of the concrete with FRP-RA. No discernible difference was observed between SSC and NC with respect to FRP-RA. Finally, a widely adopted stress-strain model for FRP-confined NC was first evaluated using the test results, and a modified stress-strain model was then proposed for more accurate predictions.