Performance of reactive powder concrete with different fibres after high-temperature exposure

Reactive powder concrete (RPC) is used in structures such as radioactive storage plants, tall buildings and power plants. The performance of RPC after high-temperature exposure is therefore important. RPC (110 MPa) was prepared with different fibres (polypropylene fibres (PPF), polyester fibres (PEF) and their combination) at an optimum fibre dosage of 0.5% by weight of cement. The fibre-reinforced RPCs were exposed to temperatures of 200–800°C for different durations (30–120 min). Physical characteristics like colour change, fracture formation, weight loss, water absorption and residual compressive strength were evaluated. Ultrasonic pulse velocity tests were conducted. Scanning electron microscopy was used to observe the microstructure and assess the deterioration of hydrated substances after exposure to extreme temperatures for different durations. An increase in compressive strength was found for all fibre-reinforced RPCs after heating to 200°C for up to 120 min. The strength increased for 30-min exposure to 400°C. The strength of the fibre-reinforced RPCs decreased for all durations of 600°C and 800°C exposure. At these temperatures, the PEF-reinforced RPC had 10–15% greater residual strength than the RPCs. The PPF-reinforced RPC absorbed 6–12% more water than the RPCs made with PEF fibres after 120 min exposure to 800°C.