Evaluation of Sample-Electrode Contact Impedance in Two-Point Measured AC Impedance Spectroscopy of Cement-Based Materials

Abstract

In this study, AC impedance spectroscopy measurements of cement paste with 0.5 W / C were collected and interpreted using different electrode-sample contact methods. The results indicated that when using a conductive glue contact (CG), two capacitive loops and an inclined line appeared within the frequency range of 100-0.1 Hz. An equivalent circuit, R s ( C d1 ( R ct Z w)) ( R d2 C d2), was proposed for contact impedance of the electrode-sample interface, and correction of error caused by the contact impedance of electrode-sample indicated that the contact impedance had almost no effect on the ACIS measurements of the cement paste with CG contact in the present curing conditions. When the samples were cured in a fog room, the CG and electrode pre-casting (EP) contact had similar interpreted parameters ( P cp). However, the demolded sample-electrode (DS) contact method and the drying environment used in the manufacture of the EP contact can significantly change P cp. In this situation, both of CG and EP contact are reasonable for ACIS measurements of cement-based materials. EP contact cannot be used for samples cured in a drying environment, and DS contact cannot be recommended for ACIS measurements of cement-based materials.