effect of fibre content and specimen shape on residual strength of polypropylene fibre self-compacting concrete exposed to elevated temperatures

This experimental study investigates the effect of specimen shape on residual mechanical properties of polypropylene (PP) fibre self-compacting concrete (SCC) exposed to elevated temperatures from 200 to 600 °C. Various shaping regimes were used including cylindrical and cubical shapes for a series of durations of 2 and 4 h, and air cooling to the room temperature before testing. The temperature determination results prove that the shaping regimes caused an action of “thermal shock” to SCC under elevated temperatures, characterized by a high temperature at fixed time of exposure. The experimental results indicate that, compared cylindrical specimen with cubical one, thermal shock induced by cylindrical shape air cooling caused more severe damage to concrete in terms of greater losses in compressive strength than those with cubical shapes. The fact that the impact of shapes on mechanical properties indicates that shaping could cause thermal shock to specimens, which is in good agreement with the results of the temperature determination. PP fibre can enhance residual strength and fracture energy of concrete subjected to thermal shock induced by air cooling from high temperatures up to 600 °C to room temperature.