Early-age characterisation of Portland cement by impedance spectroscopy

This paper applies alternating current impedance spectroscopy to assess the effect of different sand, anhydrite, and water contents on the electrochemical response of Portland cement in the early stages of hydration. Potential factors that may affect impedance measurements and data interpretation are also discussed, such as the complexity of cement chemical composition, its physical properties and hydration kinetics, and technique limitations. The impedance data obtained are benchmarked against different supporting techniques and literature data, showing a strong relationship among hydration rates as determined by thermochemistry, setting time measurements by physical approaches, pore fluid chemistry, electrical conductivity, and the impedance behaviour observed. The results demonstrate that ACIS is a sensitive technique to assess cement hydration, enabling differentiation of changes in the water and cement content, hydration degree, and microstructural development during the first 24 hours after mixing.