Results demonstrated that the total charge passed during the 6 hour ASTM C 1202 rapid chloride test (RCT) was not an accurate indication of specimen conductivity. For every mixture proportion studied, the shorter specimen had a disproportionately greater total charge passed. This would be expected based upon the effects of ohmic heating.
A measurement of the initial current (t = 0) during the ASTM C 1202 rapid chloride test provides an estimate of specimen conductivity which is typically within 5 % of the value determined from impedance spectroscopy using a frequency spectrum of 10 Hz to 1 MHz. These results were confirmed using otherwise similar specimens of different lengths. Based upon the Nernst-Einstein relationship between specimen conductivity and specimen diffusivity, these results imply that an instantaneous measurement of current can yield quantitative information about the diffusivity of the specimen. Further, data obtained during the start of the RCT suggest that the DC current measured at any time during the first few minutes of the test would yield similar results.
Impedance spectroscopy impedance plane plots also revealed an electrochemical feature in tests performed later in the experiment. This feature may be attributable to corrosion of the brass electrodes. The feature was responsible for a small bias (less than a 10 % difference) between bulk conductivities measured by impedance spectroscopy and the initial RCT current. Therefore, this suggests that implementing a rapid test based only on the initial current may require frequent monitoring of the electrode surface condition, or the use of electrodes made out of material that does not corrode in the testing solutions.