- Author
-
Campo, M. A.
|
Woo, L. Y.
|
Mason, T. O.
|
Garboczi, E. J.
- Title
- Frequency-Dependent Electrical Mixing Law Behavior in Spherical Particle Composites.
- Coporate
- Northwestern Univ., Evanston, IL
National Institute of Standards and Technology, Gaithersburg, MD
- Journal
-
Journal of Electroceramics,
Vol. 9,
No. 1,
49-56,
October 2002
- Keywords
-
composite materials
|
mixing
|
cements
|
impedance
|
electrical conductivity
|
mixing laws
- Abstract
- 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 particle composites.