Performance of hybrid fibres on mechanical properties of self-compacting concrete at elevated temperature

Purpose The present experimental investigation attempts to study the behaviour of hybrid fibre-reinforced self-compacting concrete (HFSCC) subjected to elevated temperature. The purpose of this study is to find out the performance of hybrid fibres of 0.5 per cent by volume of concrete (out of which 75 per cent are steel fibres and 25 per cent, polypropylene fibres). Reinforced beams were casted and tested for the flexural load-carrying capacity, and comparisons were made with the load-carrying capacity of reinforced beams without the inclusion of fibres. Design/methodology/approach The study includes 60 concrete cubes of 150 mm and 60 beams of 150 x 150 x 1,100 mm reinforced with minimum tension reinforcement according to IS 456-2000. The specimens were subjected to elevated temperature from 100 degrees C to 500 degrees C with an interval of 100 degrees C for 2 h. The residual compressive strength and the load-carrying capacity of beams for 5-mm deflection were measured. Parameters such as load at first crack, width and length of cracks developed on the beam during the application of load were also studied. Findings The result shows that for self-compacting concrete without fibres (SCCWOF), there is a gain in compressive strength between 200 degrees C and 300 degrees C, beyond which the strength decreases. For HFSCC, the gain in strength is between 300 degrees C and 400 degrees C, and thereafter the strength gets reduced. The load-carrying capacity of beams reduces with an increase in temperature. An increase in load-carrying capacity (up to 40.7 per cent) for HFSCC beams is observed when compared to SCCWOF beams at 500 degrees C. Originality/value Better performance was observed with the usage of fibres when the specimens were subjected to elevated temperatures.