Currently, considerable attention has been paid to measuring and interpreting the electrical properties of cement-based structural elements such as those made of concrete. Among those, electrical measurement was initially used as an investigative technique for monitoring hydration process of Portland cement. So far, the applications have been broadly expanded as a potentially powerful method in characterizing microstructural evolution and pore structure development in cementitious materials. Hence, electrical properties measurement can provide beneficial information about the material compositions and mechanical properties of concrete. One of the most important mechanical properties of concrete is the mechanical strength. This research develops some of the current advancements in electrical property measurement of concrete materials in order to investigate the relationship between electrical resistivity of concrete and the corresponding mechanical strength. Moreover, this research aims to use electrical resistivity for prediction strength of concrete non-destructively, as a new approach.
Electrical Impedance Spectroscopy (EIS) technique was used for four concrete mixtures, with two-terminal probe method. Impedance spectra obtained by EIS of the concrete samples were investigated as function of the specimen age. Compressive strength test was performed using same cylindrical material components and at the same age of specimens. Two important parameters of the impedance spectra, bulk resistance and cut-off frequency, are found to be correlated with concrete strength gain during curing of each mixture. These relationships were also considered among different mixtures at the same age.
Base on our results, we have shown that the strength of concrete can be numerically estimated by the A.C. features of cementitious materials. The experimental data indicate that: as the strength of concrete increases, the bulk resistance/bulk resistivity increases; while the cut-off frequency decreases. Then, the equations for estimating strength of concrete were obtained. Finally, further research issues will be suggested for implementation of the proposed approach.

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