Carbonation Study of Cement-Based Material by Electrochemical Impedance Method

Electrochemical impedance spectroscopy (EIS) is adopted in this study for assessing the carbonation behavior of cement-based materials, including ordinary portland-cement paste, cement mortars, and blended cements with fly ash and slag. A new equivalent circuit model was proposed and demonstrated for satisfactory interpretation of impedance spectrum of cement-based materials affected by carbonation. Experimental results show that carbonation can increase the diameter of impedance curve for all the cement-based materials. The type of cement-based material has great impact on carbonation process, which can be distinguished from the measured impedance spectrum. Functional relationships among charge transfer resistance, carbonation time, and carbonation depth are obtained, which can provide an effective way to predict the carbonation depth of various types of cement-based materials. This research's findings demonstrate that EIS method has a robust capacity for carbonation assessment and it is expected to complement the existing testing standards for the durability evaluation of construction materials.