Electrochemical impedance interpretation of the carbonation behavior for fly ash–slag–cement materials

Abstract In this paper, a new electrochemical model was adopted to study the carbonation behavior of fly ash–slag–cement materials. For a range of time spans, the parameters fitted from the equivalent circuit model were obtained by electrochemical impedance spectroscopy (EIS) measurements. By means of triangular contour plots, correlations in the time evolution of isograms of both the model parameter and carbonation depth of fly ash–slag–cement materials were analyzed. The results indicate that carbonation may also play a major role in increasing the impedance arc and the model parameters. The amount of mineral admixture becomes decisive for the variations of impedance spectra, model parameter and carbonation depth. The experimental results show that carbonation depth of fly ash–slag–cement materials is quantitatively related to the increment of the model parameter ( R ct1 ). On the contour map, the trends of carbonation depth are correlated to the variation in the increment of R ct1 . As a result, it is possible to predict the carbonation depth of fly ash–slag–cement materials with any fly ash and/or slag contents.