Effect of polycarboxylate superplasticizer on contribution of interfacial transition zone to electrical conductivity of portland cement mortars

The effect of a polycarboxylate high-range water-reducing admixture on the electrical conductivity and interfacial transition zone (ITZ) characteristi cs of portland cement mortars was evaluated using AC impedance spectroscopy , mercury intrusion porosimetry, and two electrical conductance models: the interfacial excess conductance and Bruggeman's asymmetrical effective medi um theories. Mechanical tests were also performed. Mortar specimens used ha d sand-cement ratios (s/c) of 0.5 1.0, and 1.5 aqueous high-range water-red ucing admixture dosages of 0, 0.3, and 0.75% (by mass of cement) and a wate r-cement ratio (w/c) of 0.35. The results showed that the presence of the p olycarboxylate high-range water-reducing admixture had positively modified the interfacial transition zone performance and the microstructural charact eristics of the hardened mortars. It was found, however, that this high-ran ge water-reducing admixture reduced the rate of hydration during the first day.