Evaluation of fire-damaged concrete using impact-echo method

An application of the impact-echo method for fire-damage detection on concrete using a wavelet time-frequency technique is presented here. The goal of the study was to find a correlation between the response of the impact-echo tests and the fire-damage. Before starting with non-destructive evaluation of fire-damage on concrete, visual inspection, microstructural analysis by XRD and mechanical tests were carried out. Then, the characteristics of impact-echo signals acquired in points with different levels of damage were processed by wavelet analysis. The impact-echo tests were carried out on the external surface of undamaged and damaged structural elements of a reinforced concrete building and then analysed to evaluate how fire affected the response of the material. Information about concrete degradation, temporal location and energy content of the harmonic components was successfully obtained from the scalogram of the signal. The effect of fire-damage was reflected in the scalogram of the signal.