An Indirect Impedance Technique to Determine Reinforcing Steel Properties
Following the procedure of Huang et al.5, the electrode kinetics are expressed as an oscillating current density as the summation of a charging and faradaic current. The grout is modeled as a uniform conductivity media and Laplace’s equation is used to solve for the potential distribution. The impedance is simulated over a range of frequencies as the potential difference between two reference electrodes divided by the current of the working electrode. The results are compared to experimental measurements throughout the hydration process.
The effectiveness of this method relies on the use of accurate representations of the steel surface impedance. Passive film models developed from rotating disk experiments in simulated pore solution are used to describe the steel boundary condition in the finite element model. The simulated results incorporating these models show a similar impedance response as the measured impedance of an aged cylinder put through a wetting and drying cycle.
Barring an accurate model, this technique has the potential to effectively determine the interface properties of the embedded steel from the overall response of the system.
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