Experimental investigation on fire endurance and residual strength of reinforced concrete beams strengthened with CFRP grids

Fiber-reinforced polymer (FRP) reinforcement is known to be extremely susceptible to deterioration of mechanical properties when exposed to fire. FRP grids encased with polymer mortar have received much attention lately as an efficient and fire-resistant technology for strengthening concrete structures. An experimental investigation was undertaken to examine and document the performance of carbon-fiber-reinforced polymer (CFRP) grids strengthened reinforced concrete beams under the sustained service load and the standard fire. Tests results on fire indicated that, even without any insulation, the CFRP grids strengthened beam can achieve a satisfactory fire endurance of more than 2 hours. The polymer mortar layer allows the strengthened beam to have longer fire endurance time than the un-strengthened beam, while under larger service loads. Moreover, this paper also presents a residual strength study of fire-tested beams. It has demonstrated that, if the FRP grids are able to maintain below the decomposition temperature when exposed to fire, the FRP grids strengthening system will be able to retain almost full effectiveness after cooling down.