Frequency-Dependent Electrical Mixing Law Behavior in Spherical Particle Composites.
Frequency-Dependent Electrical Mixing Law Behavior in
Spherical Particle Composites.
Campo, M. A.; Woo, L. Y.; Mason, T. O.; Garboczi, E. J.
Journal of Electroceramics, Vol. 9, No. 1, 49-56,
composite materials; mixing; cements; impedance;
electrical conductivity; mixing laws
The electrical properties of cement-based composites
with mono-size conductive (steel) or insulating (glass)
spherical inclusions were investigated by combined
2-point impedance spectroscopy and 4-point DC resistance
measurements. The matrix was ordinary Portland cement
(w/c=0.4; cured for 7 days). Particle loading was varied
over an extended range to as high as 42% volume
fraction. The steel particle composites behaved like
the glass particle composites at DC and low AC
frequencies; conductivity decreased with increasing
particle loading. Under AC excitation, however, the
steel particles were rendered conductive; conductivity
increased dramatically with particle loading. The
results were analyzed in terms of various mixing laws
and effective media theories and the proposed
"frequency-switching coating model," which accounts for
the unusual frequency-dependent behavior of the steel