Abstract
A numerical model has been developed to simulate the transport of several ionic species across a saturated concrete or mortar sample. The chloride binding as well as the electrical coupling between the different ionic fluxes are included in the model by using the Nernst-Planck system of equations. This model highlights which parameters affect substantially chloride penetration into reinforced concrete structures and then shows that the use of Fick’s first law in a predictive model for chloride penetration is strongly challenged. The simulations are in good agreement with diffusion-cell experiments and membrane potential measurements.
Résumé
Un modèle numérique a été développé afin de simuler le transport de plusieurs espèces ioniques dans une éprouvette de béton ou de mortier saturée. La fixation des ions chlorures ainsi que le champ électrique créé par les divers flux ioniques sont modélisés à l’aide d’un système d’équations de Nernst-Planck. Le modèle permet, premièrement, de mettre en évidence les paramètres qui influencent le plus la pénétration des ions chlorures et, deuxièmement, il montre que l’utilisation de la 1e loi de Fick dans un modèle de prédiction de la pénétration des ions chlorures est fortement remise en cause. Les résultats sont en accord avec les expériences de diffusion et les mesures expérimentales du potentiel de membrane.
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Editorial Note Prof. Jean-Pierre Ollivier is a RILEM Senior Member. He works at the LMDC, a RILEM Titular Member and participates in RILEM TCs 170-CSH (The structure of C-S-H) and 178-TMC (Testing and modelling chloride penetration in concrete). Prof. Lars-Olof Nilsson is a RILEm Senior Member.
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Truc, O., Ollivier, J.P. & Nilsson, L.O. Numerical simulation of multi-species diffusion. Mat. Struct. 33, 566–573 (2000). https://doi.org/10.1007/BF02480537
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DOI: https://doi.org/10.1007/BF02480537