Evaluation of residual mechanical properties of concrete after exposure to high temperatures using impact resonance method

After exposure to high temperature, concrete suffers degradation of its mechanical properties, such as its mechanical strength and elastic modulus, and these residual properties must be evaluated using various destructive and nondestructive methods in order to determine the durability of concrete structures. This study aims to investigate the change in the dynamic elastic modulus of concrete after exposure to high temperature depending on various experimental conditions including mixture proportions, exposure temperatures, post-fire storing period, and post-fire curing regimes. For this purpose, an improved impact resonance method is proposed for measuring the identical resonance frequency of the sample and for evaluating the dynamic elastic modulus, and an experimental study is performed on a total of 350 concrete samples. Accordingly, the estimating equations were obtained in order to evaluate the tensile and compressive strengths of the concrete samples based on a correlation analysis with the measured dynamic elastic modulus.