Estimation of Effective Diffusion Coefficients and Non-Linear Binding Parameters of Chloride by Reverse Analysis of Chloride Profiles

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Title: Estimation of Effective Diffusion Coefficients and Non-Linear Binding Parameters of Chloride by Reverse Analysis of Chloride Profiles

Author(s): K. Yamada, Y. Hosokawa, D. Mori, Y. Yamada, and B. Johannesson

Publication: Special Publication

Volume: 234

Issue:

Appears on pages(s): 39-52

Keywords: chloride; chloride binding; effective diffusion coefficient; EPMA; finite-difference method; numerical calculation; reverse analysis

Date: 3/22/2006

Abstract:
Instead of the conventional method for evaluating an apparent diffusion coefficient of chloride ions (Cl-) from experimental Cl- concentration profile, this study introduces a novel method to estimate an effective diffusion coefficient (De) and non-linear binding parameters (a, b) of Cl- from a Cl- concentration profiles measured by electron probe micro analysis (EPMA). This estimation is made by the combination of numerical analysis by the finite-difference method of the non-linear diffusion equation and optimizing calculations. By using this method, De, a and b are estimated for several kinds of concrete having various type of cement and several levels of water-cement ratio. The estimated values of De show a positive linear relationship with values of De obtained by migration tests. The estimated values of a show a good correlation with the alumina content in cement as expected. These results indicate the validity of this method for estimating parameters required for predicting future Cl- concentration profiles.