Prediction of chloride binding isotherms by analytical model or numerical inverse analysis

Title: Prediction of chloride binding isotherms by analytical model or numerical inverse analysis
Author(s): Véronique Baroghel-Bouny, Xiaomeng Wang, Mickaël Thiéry
Paper category : conference
Book title: 2nd International Symposium on Service Life Design for Infrastructures
Editor(s): K. van Breugel, Guang Ye, Yong Yuan
Print-ISBN: 978-2-35158-096-7
e-ISBN: 978-2-35158-097-4
Publisher: RILEM Publications SARL
Publication year: 2010
Pages: 513 - 526
Total Pages: 14
Nb references: 36
Language: English

Abstract: In this paper, various methods of prediction of chloride binding isotherms (CBIs) of cementitious materials at equilibrium and in saturated and isothermal conditions are proposed.
The first group of methods consists in numerical inverse analysis of an experimental total chloride concentration profile. The inverse analysis is carried out by means of a numerical multi-species transport model based on Nernst-Planck equation, where the CBI is described globally by Freundlich’s equation. An optimization procedure is used to assess Freundlich’s equation parameters. In addition to the CBI, the free chloride concentration profile is predicted. In this group, method 1.1 requires as input data the effective chloride diffusion coefficient (DCl-), while method 1.2 predicts DCl-. The second group of methods is an analytical model based on the composition of the material. In this case, physical adsorption onto C-S-H and formation of Friedel’s salt by chemical reactions are addressed separately.
However, Friedel’s salt formation is assumed as instantaneous and independent of the chloride concentration. The CBI is thus described by a formula, which includes a physical and a chemical component. These components involve respectively the C-S-H content and the residual content of equivalent aluminates of the material, at the considered age, which are computed by an analytical hydration model. The various methods in this group differ by the description of the physical component. Numerical and analytical CBIs, as well as predicted DCl- and profiles, have been compared to experimental data for various cementitious materials (with and without SCM) and ages. The excellent agreement observed between predicted and experimental results, as well as between analytical and numerical results, demonstrates the reliability and the accuracy of the proposed methods.

Online publication: 2011-04-20
Publication type : full_text
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