Determining the Optimal Frequency and Perturbation Amplitude for AC Electrical Resistance Measurements of Cement-Based Materials Using Harmonic Analysis

Abstract

Abstract Measuring electrical resistivity is becoming a desirable method for evaluating the material property in cement-based materials. As a rapid nondestructive technique, measurement of resistivity is frequently performed both in laboratory specimens and on-site structures. Alternating current/potential (AC)-based methods are common approaches to measure the resistivity in cement-based materials. The alternating perturbation amplitudes applied range from several millivolts to even volts. However, how the perturbation amplitude influences the results, and what are the optimal frequency and perturbation amplitude are still in question. In the present study, AC resistance measurements using electrochemical impedance spectroscopy were performed on cement-based specimens with different compositions. To investigate the effect of perturbation amplitude on the measured resistance, different amplitudes of potential perturbation varying from 5 mV up to 1,000 mV were applied. The reliability of data was evaluated by the harmonic analyses. Results indicated that, as the resistivity of specimens increased, a slight decrease in the fR (i.e., the frequency at which the ohmic resistance is measured) was observed. Noticeably, significant scatter in fR was demonstrated by applying different potential perturbations, especially for amplitudes lower than 50 mV. In terms of the perturbation amplitude, the results of resistivity were generally maintained in a relatively small variation when the potential perturbation was higher than 100 mV. Based on harmonic analyses, the appropriate frequency and perturbation amplitude for measuring the resistance of cement-based materials were determined.