In situ electrochemical impedance characterization of cement paste with volcanic ash to examine early stage of hydration

An experimental investigation using Electrochemical Impedance Spectroscopy (EIS) was carried out when Portland cement was replaced by natural pozzolanic volcanic ash obtained from Saudi Arabia. The cement pastes were sequentially measured with EIS during the early stage of hydration for up to 3 h. Nyquist, Bode and frequency versus phase angle plots were used to evaluate the effect of substitution and particle size of volcanic ash with Portland cement. Warburg impedance was used as a measure to evaluate the chemically bound water during the early part of hydration. This study shows that EIS is a powerful technique for examining the early age water dynamics when naturally available additives such as volcanic ash are used as partial substitutes to Portland cement.