| Summary: | Ultra-high performance fibre reinforced concrete (UHPFRC) possesses favourable mechanical properties in comparison with normal strength concrete. Despite a surge in interest among researchers and industries over the past decade, there is negligible research data on the performance of UHPFRC in fire. This situation is compounded by the lack of design guidelines of UHPFRC in major structural design codes both at ambient and at elevated temperatures. The experimental work conducted was divided into three parts. The first part involved casting and testing of nine beams for flexure at ambient temperature. The beams were reinforced with steel fibres at 1, 2 and 4 vol. % and cured in two different conditions (20 °C and 90 °C water). In the second part, nine beams with two different steel fibre dosages (2 and 4 vol. %) were tested at elevated temperatures under an ISO 834 standard fire curve. Seven of these were tested while loaded at three different loading levels (0.2, 0.4 and 0.6). The other two, cured in different conditions, were tested unloaded at elevated temperatures to study the influence of the curing temperature. The third part involved determining the residual strength of the UHPFRC. The residual strength tests sought to investigate the influence of the curing temperature on the strength degradation of UHPFRC, with the aim of understanding the post-fire analysis and repairs. A finite element model was created using DIANA software followed by a parametric study. In the ambient temperature tests, the hot-cured beams recorded higher compressive strength. However, despite having lower compressive strength, the cold-cured beams had the higher load bearing capacity. Exposure of beams to fire was characterised with explosive spalling. Spalling was more prevalent in beams containing 2 vol. % of steel fibres. The beams under the 0.4 load level spalled significantly more than the other two load categories and had the least fire resistance. The addition of polypropylene fibres eliminated spalling and effectively increased the fire resistance of the beam. The curing temperature had an influence on the fire performance of the beams, the hot-cured beam spalled significantly more than the cold-cured. The findings from the residual strength tests indicated that the relative residual strength of cold-cured elements was higher than the hot-cured.
|
|---|
