Effect of carbon dioxide curing on cement pastes through DRT analysis of EIS data

Early-age carbon dioxide curing (EACC) is one of the promising methods for carbon dioxide (CO2) sequestration and utilization in cement-based materials which, in addition to CO2 mineralization, has the potential to improve the engineering properties of construction materials. Understanding the effect of EACC on the electrochemical properties of hydrated cement provides an insight for its hydration evolution and mechanical performance. In this study, the effect of EACC on the electrical properties of cement pastes with various water contents using electrochemical impedance spectroscopy (EIS) was investigated. The conventional method for interpretation of EIS data is fitting Nyquist plots by equivalent circuits models (ECMs), however, this method does not provide accurate analysis at early age hydration. Instead, the distribution of relaxation times (DRT) method for extracting parameters of electrochemical interfaces and time domain properties was proposed. Using the DRT analysis, two peaks were identified in the EIS data representing two interfaces in the electrochemical cell including the electrode-cement and pore structure interfaces. The parameters of each interface were extracted. The results show that cement bulk resistance, the resistance of the electrode-cement interface, and the pore structure resistance of the cement paste profile increased with respect to CO2 curing.