Protecting Concrete Power Poles from Stray Alternating Current

 Aghajani Koupaee, A., Golozar, M. A., Saatchi, A.,  Raeissi, K., Urgen, M., Shabani, S.

Materials Performance, Cathodic & Anodic Protection, Vol 52, No. 10, October, 2013

Abbstract :

The purpose of this work was to investigate how the impedance of concrete subjected to alternating current (AC) is affected by adding silica fume, reducing water-to-cement ratio, and adding polypropylene fibers. Based on the test results, it is possible to increase concrete impedance and decrease its susceptibility to degradation by AC voltage.

Conrete pores can act as capacitors and alternating current (AC) can pass through a capacitor. Thus Ac, passes in concrete in tow parallel ways by capacitor and resistor paths. The capacitor paths consist of the pore network and resistor paths consist of the solid phase. If steel bars are embedded in the concrete, then the bars can also act as capacitors for passing AC.1-3 As shown in Figure 1, there are two kinds of capacitors in concrete’s equivalent of an electrical circuit. Therefore, three steel bars embedded in concrete can be used as working, counter, and reference electrodes during an electrochemical impedance spectroscopy (EIS) test. According to Figure 1, the EIS spectrum of concrete consists of two arcs, one that is related to the capacitance of the steel bars and appears in the low-frequency range, and another that is related to the capacitance of the bulk concrete and appears in the high-frequency range.