Effect of curing temperature on the behaviour of UHPFRC at elevated temperatures

Ultra-high performance fibre reinforced concrete is one of the construction materials that is still in need of more research to evaluate its performance under fire, particularly regarding explosive spalling. In this study, the effect of curing temperature on the fire resilience of ultra-high performance fibre reinforced concrete (UHPFRC) has been tested. In particular, the influence of cold (20 °C) and hot (90 °C) water curing temperatures on the performance of UHPFRC exposed to elevated temperatures has been investigated. Beams, cured in cold water and in hot water were tested under the standard ISO 834 heating regime. The test results showed that the beam cured in hot water spalled significantly more than the beam cured in cold water. The study further investigated the influence of curing temperature on the residual strength of UHPFRC (containing both steel and polypropylene fibres). The cube elements were heated at eight selected temperatures between 200 °C and 900 °C. The cold-cured concrete exhibited higher relative residual strength at all temperatures. The results further showed that UHPFRC have high strength retention up to 600 °C. The residual peak strength for both the cold and the hot-cured occurred at 400 °C.