Effect of fire insulation on fire resistance of hybrid-fiber reinforced reactive powder concrete beams

This paper presents the result of tests conducted on four hybrid-fiber reinforced reactive powder concrete (RPC) beams protected with fire insulation exposed to fire. The thermal fields, structural responses, fire endurance, failure modes, and crack patterns of the beams were measured and recorded during the tests. The experimental results indicate that the failure of reinforced RPC beams with fire insulation was driven by direct fire exposure and fracture of the longitudinal rebars after fall of the fire insulation on the beam. At elevated temperatures, RPC beams with fire insulation that are under-reinforced at room temperature may fail as the lightly reinforced beams. The post-fire test observation reveals that no fire-induced spalling occurred in the reinforced RPC beams (moisture content range 2.12–4.06%) under fire conditions owing to the use of hybrid fibers (2% of steel fibers and 0.2% of polypropylene fibers) and fire insulation at the same time. Furthermore, based on the test results, the effect of three significant parameters on the response of fire exposed reinforced RPC beams was investigated: cover thickness of RPC, load ratio and fire insulation thickness. Additionally, a comparison of the fire response between uninsulated and insulated RPC beams is also presented.