Performance evaluation of fiber-reinforced reactive powder concrete exposed to high temperature combining nondestructive test

Abstract

An experimental study has been performed in an attempt to evaluate the performance of fiber-reinforced reactive powder concrete (RPC) after high temperatures using nondestructive methods. In this context, four RPC mixtures containing 2% steel fibers and 0–0.2% polypropylene (PP) fibers were produced. After samples exposure to various temperatures 20 °C, 100 °C, 200 °C, 300 °C, 400 °C, 500 °C, 600 °C, 700 °C and 800 °C, different non-destructive tests (NDTs) including ultrasonic pulse velocity (UPV) and resonance frequency (RF) as well as sound velocity calibration tests were conducted. Besides, specimens damage roughly assessed by physical observation and mass loss. Further on, mechanical performance was evaluated by axial compressive strength, and scanning electron microscopy (SEM) was employed to understand the high temperature deterioration mechanism of RPC specimens. The results indicated that mass loss and NDTs parameters values gradually deteriorated with the increasing temperature. Additionally, the compressive strength raised up to 200 °C. Nevertheless, it dropped dramatically from 200 °C to 700 °C. After that, the strength increased mildly. The weight loss and residual strength as well as NDTs parameters were related to temperature and fiber content. Moreover, quantitative description formulas of mentioned factors were presented. It was also found that 2% steel fiber and 0.15% PP fiber seems to be the optimal fiber combination always performed better in comparison with other fiber contents regarding the residual compressive strength and NDTs parameter values. Furthermore, the regression equations between compressive strength and NDTs values have been provided with all correlation coefficients exceed 0.95. The research demonstrated the potential of the NDTs methods for application of fiber-reinforced RPC exposed to high temperatures.