Compressive behaviour of hybrid fiber-reinforced reactive powder concrete after high temperature

This study focuses on the compressive properties and microstructures of reactive powder concrete (RPC) mixed with steel fiber and polypropylene fiber after exposure to 20–900 °C. The volume dosage of steel fiber and polypropylene fiber is (2%, 0.1%), (2%, 0.2%) and (1%, 0.2%). The effects of heating temperature, fiber content and specimen size on the compressive properties are analyzed. The microstructures of RPC exposed to different high temperatures are studied by scanning electron microscope (SEM). The results indicate that the compressive strength of hybrid fiber-reinforced RPC increases at first, then decreases with the increasing temperature, and the basic reason for the degradation of macro-mechanical properties is the deterioration of RPC microstructure. Based on the experimental results, equations to express the relationships of the compressive strength with the heating temperatures are established. Compared with normal-strength and high-strength concrete, the hybrid fiber-reinforced RPC has excellent capacity in resistance to high temperature.

► We complete the high temperature test and compression test of RPC after 20–900 °C.
► The presence of steel fiber and polypropylene fiber can prevent RPC from spalling.
► Compressive strength increases first and then decreases with elevated temperatures.
► Microstructure deterioration is the root cause of macro-properties recession.
► Equations to express the compressive strength change with temperature are proposed.