Calculation of Ionic Diffusion Coefficients on the Basis of Migration Test Results

Published

April 1, 2003

Author(s)

E Samson, J Marchand, Kenneth A. Snyder

Abstract

Migration tests are now commonly used to estimate the diffusion coefficients of cement-based materials. Over the past decade, variousapproaches have been proposed to analyze migration test results. In many cases, the interpretation of test data is based on a series of simplifying assumptions. However, a thorough analysis of the various transport mechanisms that take place during a migration experiment suggests that some of them are probably not valid. Consequently, a more rigorous approach to analyze migration test results is presented. The testprocedure is relatively simple and consists in measuring the evolution of the electrical current passing through the sample. Experimental resultsare then analyzed using the extended Nernst-Planck-Poisson set of equations. A simple algorithm is used to determine for each experiment the tortuosity factor that allows to best reproduce the current curve measuredexperimentally. The main advantage of this approach resides in the fact that the diffusion coefficients of all ionic species present in the system can be calculated using a single series of data. Typical examples of the application of this method are given. Results indicate that the diffusion coefficients calculated using this approach are independent of the applied voltage and depends only slightly on the concentration level and the chemical make-up of the upstream cell solution.

Citation

Materials and Structures

Volume

35

Issue

No. 257

Pub Type

Journals

Download Paper

Local Download

Keywords

concrete, diffusion, duffision potential, migration, Nernst-Planck

Citation

Samson, E. , Marchand, J. and Snyder, K. (2003), Calculation of Ionic Diffusion Coefficients on the Basis of Migration Test Results, Materials and Structures, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=860487 (Accessed December 15, 2024)