Concrete Electrical Conductivity Test

The purpose of this form is to compute the results of a bulk electrical conductivity of concrete (ASTM C1760) test and estimate an equivalent response in rapid chloride permeability (RCP) testing (ASTM C1202). The RCPT result is adjusted for the size difference (if any) between specimens in the two tests, assuming that the C1202 test is always conducted on 95.25 mm diameter x 50.8 mm long cylinders. To perform the computations, the user fills in the input fields and the results are updated when an input field is changed or upon request by clicking on the Compute button. Please note that per the C1760 standard, the input measured current is in units of milliamps (mA).

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Input parameters from C1760 testing

Specimen diameter: mm

Specimen length: mm

Applied voltage: V

Measured current at 1 minute: mA

Computed bulk electrical conductivity: mS/m

Computed bulk electrical restiviity: Ohm-m

Estimated RCPT charged passed (in 6 h): C

(no Joule heating effects are included in the above estimate for RCPT charge passed)

Estimated RCPT charged passed (in 6 h) with Joule heating: C

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What about chloride ion diffusion?

According to the Nernst-Einstein relation, the ratio of the bulk electrical conductivity of the concrete specimen to the elecrical conductivity of the pore solution within it should equal the ratio of the diffusion coefficient of chloride ions in the concrete to their diffusion coefficient in the pore solution. The latter is usually assumed to be the same as the value for chloride ions in bulk water, or about 1.8x10^-9 m²/s (Mills and Lobo). This doesn\'t include the influences of binding and reactions of the chloride ions by the cementitious materials that slow the apparent diffusion and consequently typically produce a reduced apparent diffusion coefficient. The electrical conductivity of the pore solution can be estimated from the alkali composition of the cementitious binder as outlined by Snyder et al. (2003) and implemented as a web application (Bentz, 2007) that is available by clicking here. The web application performs estimations of the pore solution conductivity under either saturated or sealed curing conditions and also provides for a user selected pore solution viscosity.

Chloride ion diffusion coefficients can be used in a variety of freely available models to estimate service lifes of concrete structures including:

Life-365^TM

1-D Fickian Model

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Questions or comments:

E-mail: [email protected]

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References

ASTM C1760-12, Standard Test Method for Bulk Electrical Conductivity of Hardened Concrete, ASTM International, West Conshohocken, PA, 2012.

ASTM C1202-10, Standard Test Method for Electrical Indication of Concrete\'s Ability to Resist Chloride Ion Penetration, ASTM International, West Conshohocken, PA, 2010.

Bentz, D.P., A Virtual Rapid Chloride Permeability Test, Cement and Concrete Composites, Vol. 29 (10), 723-731, 2007.

Mills, R., and Lobo, V.M.M., Self-Diffusion in Electrolyte Solutions, Elsevier, Amsterdam, 1989, p. 317.

Snyder, K.A., Ferraris, C., Martys, N.S., and Garboczi, E.J., Using Impedance Spectroscopy to Assess the Validity of the Rapid Chloride Test for Determining Concrete Conductivity, Journal of Research of the National Institute of Standards and Technology, Vol. 105, 497-509, 2000.

Snyder, K.A., Feng, X., Keen, B.D., and Mason, T.O., Estimating the Electrical Conductivity of Cement Pore Solutions from OH^-, K⁺, and Na⁺ Concentrations, Cement and Concrete Research, Vol. 33, 793-798, 2003.