Behavior evaluation of hybrid fibre-reinforced reactive powder concrete after elevated temperatures

This research was aimed to evaluate the performance of reactive powder concrete (RPC) mixed with steel fibre and polypropylene (PP) fibre after exposure to 20 degrees C-800 degrees C. The volume contents of steel fibre and PP fibre are (2%, 0%), (2%, 0.1%), (2%, 0.15%) and (2%, 0.2%), respectively. Residual mechanical properties of cubic compressive strength and split-tensile strength were measured. Besides, physical parameters such as mass loss and appearance change after different temperatures have also been determined. The thermal deterioration of RPC is assessed by water absorption and sorptivity. Results show that the residual strength increased from ordinary temperature to 300 degrees C. However, it's decreased gradually as temperatures rise. RPC with 2% steel fibre and 0.15% PP fibre showed the best performance regarding spalling resistance and mechanical characteristics compared to the others. In addition, all specimens showed increasing in mass loss and water absorption with the increasing temperature. Based on the experimental results, equations to express the relationships of the strength with the heating temperatures are established. Distinct changes in the microstructure of RPC reveal mechanical properties from a macroperspective.