Performance evaluation of RPC exposed to high temperature combining ultrasonic test: A case study

Reactive powder concrete (RPC) with different volume fractions of steel fibers were fabricated into test specimens with dimensions of 100 × 100×100 mm for compressive strength tests and ultrasonic tests at 20, 100, 200, 300, 400, 500, 600, 700 and 800 °C, respectively. The testing results indicated that as the steel fiber content increased, the critical temperature of the explosive spalling of RPC increased correspondingly. It is also found that the incorporation of 2.5% steel fibers can effectively inhibit explosive spalling. Additionally, when the target temperature rose, the rate of mass loss of the steel-fiber-reinforced RPC increased (quickly at the beginning and slowly thereafter), and the critical temperature was determined to be 300 °C. The influence of variation in the steel fiber content on the mass loss rate of the RPC was relatively less. Moreover, the ultrasonic pulse velocity of the steel-fiber-reinforced RPC showed a decreasing trend as the temperature rose, and the descending rate initially accelerated and then slowed down. A regression equation was established, to show the correlation of the ultrasonic pulse velocity and compressive strength with temperature for RPC exposed to elevated temperatures.