Investigation of the hydration properties of cement with EDTA by alternative current impedance spectroscopy

Alternative current impedance spectroscopy (ACIS) is a promising non-destructive testing method to monitor long-term change and assess the durability of concrete. This study investigates the influences of Ethylene Diamine Tetraacetic Acid (EDTA) on the hydration of hardening cement by ACIS. It is found that EDTA retards the early-age hydration of cement but can facilitate the later age reaction. Pastes with EDTA show comparable or higher compressive strength than Control at 28 d, especially when the dosage is higher than 0.4%. Microstructural characterization results reveal the working mechanism of EDTA originating from its complexing effect on free ions. The resistivity evolution of the pastes detected by ACIS can well reflect the effects of EDTA on the cement hydration in different ages. Proportional relations are identified between the resistivity and other hydration parameters, such as reaction degree, chemical shrinkage, compressive strength. The results of this study indicate a wider prospect of ACIS in monitoring the microstructure evolution and macro-properties of cementitious materials.