Assessment of damages in concrete by the electric response parameters to pulse mechanical excitation

The paper proposes a method for assessing damages in concrete. Estimation procedure is based on the measurement of the electric responses to pulsed mechanical excitation. Measured electric response is the result of two different processes: deformation and shift by elastic wave of electric double layers arranged on the borders of the components in the concrete; and piezoelectric quartz polarization, which is contained in sand and gravel, used for concrete manufacturing. Concrete samples sized of 100x100x100 mm and 100x100x200 mm were taken for our research. Concrete samples were loaded in the system 'sample-wedge' in a hydraulic press to create and grow a crack in the sample. We used cycling freeze - thawing process for the simulation of real cracks which has a different orientation and configuration. Electric signal analysis in frequency and time domain is the basis for concrete damages estimation. Different types of mathematical calculations were applied to measured electric signals for assessment theirs changes during the process of increasing depth and concentration of cracks. Such as signal power spectral density plot in depth/density and frequency coordinates, the estimation of the selected frequency range gravity centre displacement, correlation analysis of temporal form of the measured electric signal and determining the attenuation ratio of electrical signal energy based on time-frequency analysis.