The compressive strength and flexural toughness as well as fracture energy of fiber reinforced high-performance concrete (FRHPC) subjected to different high temperatures were studied. The results showed that after exposure at 300, 600 and 900 ℃, the concrete mixes retained 88.1%, 41.3% and 10.2% of the original compressive strength on average, respectively. Steel fiber and polypropylene (PP) fiber were both effective in minimizing the damage effect of high temperatures on the compressive strength. The HPC reinforced with steel fibers showed higher flexural toughness and fracture energy before and after the high-temperature exposures. In comparison, PP fibers had minor beneficial effects on the flexural toughness and fracture energy. The mechanical properties of HPC reinforced with hybrid fibers (steel fiber+PP fiber) were equivalent to or better than those of HPC reinforced with steel fibers alone. In addition, the failure pattern of FRHPC beams changed from pull-out of steel fibers at lower temperatures (20, 300 and 600 ℃) to tensile failure of steel fibers at higher temperature (900 ℃).
The objective of this study is to increase the insight into the mechanical behaviors of steel fiber reinforced high-performance concrete (SFHPC) after exposure to high temperatures. Three types of steel fibers were used and three-point bending tests on notched beams of SFHPC were carried out . The results showed that the flexural toughness and fracture energy of SFHPC increased evidently with the fiber content. The hooked steel fibers with higher strength possess higher flexural toughness and fracture energy than the marked steel fibers with lower strength. After exposure to high temperatures of 300, 600 and 900 ℃ in an electrical furnace, the compressive strength, flexural toughness and fracture energy of SFHPC decreased less than that of HPC without fibers. Both steel fiber content and type had strong influences on the flexural toughness and fracture energy. In addition, the failure patterns of SFHPC beams changed from pull-out of steel fibers at lower temperatures to tensile failure of steel fibers at 900 ℃.
