Impedance Spectra of Fiber-Reinforced Cement-Based Composites: A Modeling Approach.
Impedance Spectra of Fiber-Reinforced Cement-Based
Composites: A Modeling Approach.
Garboczi, E. J.; Torrents, J. M.; Mason, T. O.
Cement and Concrete Research, Vol. 30, No. 4, 585-592,
composite materials; reinforced cements; electrical
The impedance response of conductive fiber-reinforced
cement-based materials was investigated using model
systems (physical simulations) consisting of conducting
needles in aqueous solutions. Two discrete bulk arcs are
observed in the Nyquist plots for fiber-reinforced
samples, while only a single bulk arc was observed for
samples without fibers. This difference is attributable
to thin, resistive, and highly capacitive layers (e.g.,
oxide film or polarization double layers) which reside
on the surfaces of the conducting fibers. These layers
fully insulate the fibers at low frequencies (near DC),
so that the highly conducting fibers behave as if they
were insulating fibers. At intermediate frequencies,
these layers short out, so that the fibers act as highly
conducting elements in the microstructure. Spreading
resistance effects from the ends of the fibers play an
important role in the high frequency behavior.
Pixel-based computer modeling results are presented to
rationalize both DC and high frequency behavior.
Experimental and modeling results are used to develop an
equivalent circuit model containing a
frequency-switchable fiber coating element.