Using Impedance Spectroscopy to Assess the Viability of the Rapid Chloride Test for Determining Concrete Conductivity.
Using Impedance Spectroscopy to Assess the Viability of
the Rapid Chloride Test for Determining Concrete
Conductivity.
(247 K)
Snyder, K. A.; Ferraris, C. F.; Martys, N. S.; Garboczi,
E. J.
Journal of Research of the National Institute of
Standards and Technology, Vol. 105, No. 4, 497-509,
July/August 2000.
Keywords:
concretes; inductivity; diffusivity; impedance
spectroscopy; rapid chloride test
Abstract:
The suitability of using the initial current from the
rapid chloride test (ASTM C 1202) to determine specimen
conductivity is tested using impedance spectroscopy with
a frequency spectrum of 10 Hz to 1 MHz. The specimen
conductivity has an analytical relationship to specimen
diffusivity and so is a useful quantity in service life
prediction. Measurements made on specimens of different
lengths indicate that the total charge passed during the
six hour conduction test carried out according to ASTM C
1202 is not a direct measure of specimen conductivity.
Further, ohmic heating during the 6 hour test makes it
nearly impossible to directly measure any specimen
transport property from the results. The total charge
passed during the 6 hour conduction test is, therefore,
not a reliable quantity for service life prediction.
Results indicate that the direct current (dc)
measurement of resistance using a voltage of 60 V is
sufficient to overwhelm polarization effects, thereby
yielding an accurate estimate of the true specimen
conductivity. Impedance spectroscopy measurements also
indicate that corrosion may form on the brass
electrodes, adding bias to a conductivity estimate based
upon a dc measurement.
