Behavior and modeling of FRP-confined ultra-lightweight cement composites under monotonic axial compression

Ultra-lightweight cement composite (ULCC) has low densities of less than 1400 kg/m(3) with a compressive strength up to 60 MPa, making them ideal for use in structures where material weight is critical. However, these applications were limited by its brittleness and low ductility. Wrapping ULCC with fiber reinforced polymer (FRP) can enhance its ultimate strain and compressive strength. This premier study and model of FRP-confined ULCC under axial compression tested 21 FRP-confined ULCC cylinders. Strength and FRP thickness were the primary variables. Test results indicated that the bearing capacity and ductility of ULCC are considerably improved by FRP jackets, which is similar to FRP-confined normal concrete (NC). It also is shown that the lateral dilation behavior of FRP-confined ULCC differs significantly from that of FRP-confined NC because the former has lower elastic modulus and more brittle feature than the latter; this difference reveals the post-peak strain hardening-softening mechanism of confined concrete. In addition, this paper introduces a new strength model with an improved stress-strain relationship for FRP-confined ULCC columns. Compared with the existing models, the proposed model can predict the stress-strain behavior of FRP-confined ULCC with better accuracy.