Advancing post-fire confinement performance of FRP jacketing with silicon-based matrix replacement

This paper investigates a silicon-based high-temperature adhesive as a matrix replacement for fibre-reinforced polymer (FRP) to serve as an alternative solution in concrete column jacketing, to address the inherent fire vulnerability of FRP composites, and enhance their suitability for structural applications. The compressive behaviour of concrete cylinders wrapped with traditional epoxy-based FRP and silicon-based matrix (SBM) FRP is examined and compared. The behaviour and effectiveness of both FRP schemes are tested after exposure to temperatures up to 800 ℃ under steady-state conditions. The enhancement of the post-heating mechanical performance of the SBM-FRP is primarily attributed to its high thermal stability and fibre-matrix compatibility, as evidenced by simultaneous thermal analysis (STA) and scanning electron microscopy (SEM). The results show that the adopted matrix replacement outperforms the traditional epoxy-based FRP, maintaining substantial strength enhancement up to 650 ℃ exposure, in conjunction with preventing fire spread (i.e., non-flammable). The superior performance of jacketed specimens with the SBM-FRP was confirmed with average compressive-strength enhancement ratios of 2.83 and 1.89 for 500 ℃ and 650 ℃ exposures, respectively. In contrast, the epoxy-based FRP–jacketed specimens first underwent matrix decomposition at 500 ℃, followed by extensive fabric oxidation at 650 ℃, resulting in an ash-like residue of the entire jacket. The feasibility of reusing the severely thermal-damaged traditional FRP jackets was examined solely for comparison with the SBM-FRP system, thereby contributing to establishing a new benchmark. In addition, the existing confinement models from the literature provide acceptable predictions for the new system at ambient temperature, leaving a certain degree of conservatism in design, indicating the adoptability of the use of SBM-FRP at ambient temperature. The results demonstrate strong prospects for the presented matrix replacement as an alternative to conventional FRP matrices used for structural confinement applications.