Study on residual behaviour and flexural toughness of fibre cocktail reinforced self compacting high performance concrete after exposure to high temperature

► The effect of different fibers on flexural toughness and residual strength of HPC before and after the burning are studied. ► The fiber influence on the formation of cracks and the failure pattern of fibers and HPC under fire has been analyzed. ► The thermal cracking behaviour of the interface between fiber and HPC matrix after fire is discussed. ► The spalling and post-peak behaviour of SCHPC with mono fibers and fiber cocktail after heating have been revealed. ► The fibre cocktail shows exccelent hybrid effect in improving the ductility and residual strength of HPC during and after fire. This paper analyzed the effect of different fibres on the residual compressive strength, the ultimate load and flexural toughness, the failure pattern and the fracture energy of self compacting high performance concrete (SCHPC) after exposure to various high temperature. The micro polypropylene fibre (PP fibre) could mitigate the spalling of SCHPC member significantly, but did not show clear effect on the mechanic properties of concrete. The macro steel fibre (SF) reinforced SCHPC showed higher flexural toughness and ultimate load before and after high temperatures. The mechanical properties of hybrid fibre reinforced SCHPC (HFSCHPC) after heating were better than that of mono fibre reinforced SCHPC. The failure mode changed from pull-out of steel fibres at lower temperature to broken down of steel fibres at higher temperature. The use of hybrid fibre can be effective in providing the residual strength and failure pattern and in improving the toughness and fracture energy of SCHPC after high temperature.