Electrochemical immittance spectroscopy applied to a hybrid PVA/steel fiber engineered cementitious composite

Alternating current (a.c.) electrical property measurements are presented on an Engineered Cementitious Composite (ECC) reinforced with a hybrid mix of polyvinyl alcohol fibers (fixed dosage) and straight steel fibers of varying dosages (0.15–1.0% by volume), with the aim at elucidating the influence of conductive inclusions on the nature of conduction and polarization processes within the composite. Measurements were undertaken over the frequency range 1Hz–10MHz at 7, 14 and 28 days after casting and the data presented in a range of formalisms to aid interpretation. When plotted in the frequency domain, the work shows that steel fibers enhance the polarizability of the material, particularly within the frequency range ~10Hz-10kHz. When presented in Nyquist format, this feature manifests itself as an intermediate arc forming between a high frequency arc (>10kHz) and a low frequency arc (<10Hz), the latter resulting from polarization processes at the sample/electrode interface. The prominence of the intermediate arc was found to be dependent upon steel fiber dosage and curing time. It is shown that the bulk electrical conductivity conforms to the equivalent inclusion theory which is a variant on the effective medium theory.