Elevated temperature resistance of ultra-high-performance fibre-reinforced cementitious composites

Elevated temperatures, specifically in the event of fire, are likely to cause extreme deterioration in fibre-reinforced polymer (FRP) strengthened reinforced concrete (RC) structures. Various types of high-performance cementitious composites (HPCC) have been explored for the protection of RC structural members against elevated temperature, but there is inadequate information in this regard for ultra-high performance fibre-reinforced cementitious composites (UHPFRCC) containing high-alumina cement (HAC) and ground granulated blast furnace slag (GGBS) in conjunction with hybrid fibres - a prospective fire-resistant UHPFRCC for structural members. In this study, the change in mechanical strength of UHPFRCC was examined before and after heat treatment, followed by thermal and microstructural analysis. Besides the control sample, three other samples containing up to 1.5% of basalt fibres, and 1 kg/m(3) of polypropylene fibres, were prepared and tested. Another mix was also prepared with only 1 kg/m(3) of polypropylene fibres. Each sample was heated to 400, 700 and 1000 degrees C. Results showed that the use of hybrid fibres significantly improved the room temperature mechanical strengths of UHPFRCC, which were found to be 80 MPa and 14.3 MPa, respectively. However, the optimum residual compressive and flexural strength was attained by UHPFRCC with only PP fibres and hybrid fibres, respectively.