Electrical conductivity of Portland cement mortars

Mortars containing volume fractions of aggregate less than 0.35 were prepared at w/c = 0.35, 0.40, and 0.45 and hydrated for 1, 14, and 28 days. Mortar electrical conductivities were determined by impedance spectroscopy, and the experimental data were fitted to the polynomial, where, sigma(m), is the mortar [GRAPHICS] conductivity, V-a is the aggregate volume, V-m is the mortar volume, and A, B, C, and D are constants. Mortar electrical conductivity behavior appears to involve a competition between the insulating aggregate which lowers the mortar electrical conductivity and the development of a transition zone between the paste and aggregate which increases the conductivity. Values for the transition zone electrical conductivity were determined.