Electrochemical impedance spectroscopy of concrete with nanoscale mineral additives

The electrochemical impedance spectroscopy (EIS) tests of concrete with nanoscale mineral additives immersed in fresh water and saline water were carried out to analyze the effects of chloride ion conditions and nanoscale mineral additives on the impedance parameters of concrete. The results showed that at the same content of mineral impurities, the pore solution resistance, the resistance of charge transfer by hydration electrons and the diffusion impedance coefficient of concrete blocks immersed in saline water were less than those immersed in fresh water; the capacitance of a double electric layer was greater than that of concrete blocks immersed in fresh water, and the constant phase angle index was basically the same. This indicated that for concrete immersed in saline water, chloride ions diffuse into concrete; as a result, the free ion concentration in the pore solution and C-S-H gel increases, the resistance of the electrolyte in the pore solution and the diffusion resistance of free charge in the porous structure of concrete decrease. However, the presence of the chloride ion did not have a noticeable effect on the characteristics of the porous structure of concrete. Under the same immersion conditions, with an increase in the content of nanoscale mineral additives, the impedance parameters of concrete such as the pore solution resistance, the charge transfer resistance of hydration electrons, the diffusion impedance coefficient and the constant phase angle index showed an increasing trend, while the double electric layer capacitance basically remained unchanged, indicating that nanoscale mineral admixtures reduce the porosity of concrete, improve the compactness of concrete and improve performance of concrete.