Effect of Different Micro Metal Powders on the Electrical Resistivity of Cementitious Composites

The electrical resistivity is an essential parameter describing materials' capacity to convey electric current. Normal cementitious materials display high estimation of the electrical resistivity because of their insulating nature. However, the high electrical resistivity of concrete can be reduced by a sufficient amount of electrically conductive admixture. Such an improvement is advantageous in self-sensing or self-heating concrete design. In this study, the effects of metal additives on the electrical resistivity of hardening cement paste were investigated. In the experiments, two different types of metal admixtures; copper powder and iron powder were used. Hybrid composition of copper and iron were also considered for comparisons of the electrical resistivity. A water to binder ratio of 0.35 was used. The metal powders were used in the mixtures by replacing the cement in ratio of 0%, 5%, 10%, 15% and 20% by weight. The total binder content (cement and metal additives) was always the same in the experiments. The measurements were carried out at room temperature by using two-electrode- AC method. The test results indicate that the metal cement composites with 20% of cement weight improved the lower electrical resistivity of the cement paste than plain cement paste. In addition, composites with copper powders had less electrical resistivity than those with iron powders. The reduction of electrical resistivity with an increase of metal content was steady for when of using hybrid composites better than when using metal powders alone. The Different frequency options 1 kHz, 10 kHz and 100 kHz were used to investigate the effect of impedance-frequency and phase angle-frequency of a sample test using the LCR meter. The highest current frequency available on the LCR meter, 100 kHz, was chosen to be used as the applied current frequency in all of the experiments which exhibit much lower phase angle values that can cancel the effect of change in electrical resistivity measurements.