Cement fraction effect on EIS response of chloride migration tests

This paper highlights the electrochemical phenomena that occur during chloride migration tests on construction materials. For this purpose, investigations by electrochemical impedance spectroscopy (EIS) were carried out on cementitious and non-cementitious materials. Materials deals with cement paste, mortar and concrete on one hand, and two types of terracotta, pink and brown, on the other hand. The results obtained for these two types of construction materials show that the electrical charge distribution within the material during the chloride transfer depends on the volumic cement proportion in the material. This was highlighted by the establishment of a plateau region at low frequencies of the EIS in the Nyquist plot. Moreover, the extension of the plateau region is closely linked to the volumic cement proportion. These electrical charges could reduce the transfer electrical current, which distorts the estimation of the diffusion coefficients obtained with accelerated tests.