Post-fire performance of GFRP-RC beams: Lap splice length and intumescent coating effects

This study examines the post-fire flexural performance of concrete beams reinforced with GFRP bars and evaluates the influence of lap splice length and intumescent paint protection. Nine beams with continuous reinforcement, 500-mm splices, and 1000-mm splices were tested. Six beams were exposed to ASTM E119 fire for 260 min, which exceeds the standard 2–3-hour fire resistance requirements. After cooling, all specimens were tested under four-point bending. Fire exposure caused severe reductions in flexural capacity, particularly in the 500 mm splice specimens, which failed by bond loss at the splice region. Beams with 1000 mm splices retained substantially higher residual capacity and exhibited failure behavior more closely resembling that of the continuous-bar specimens. Intumescent paint reduced reinforcement temperatures by up to 150–200 °C and improved residual strength by 10–15% relative to unprotected counterparts. The results establish that splice detailing remains the governing weakness of GFRP-RC members in fire and that surface protection with intumescent paint, combined with adequate splice length, can maintain measurable residual capacity after extended fire exposure. Although the paint was applied over the full fire-exposed span in this study, targeted application at splice zones represents a practical and economical protection strategy for critical regions in real structure.