Abstract
The main features of a numerical model that predicts the mechanisms of ionic transport in unsaturated cement systems are described. The model, called STADIUM, is divided into four parts: ionic diffusion, moisture transport, chemical reactions, and chemical damage. The diffusion of all ions present in the system is modeled by solving the extended Nernst-Planck/Poisson set of equations. The model takes into account the electrical coupling between the various ionic species in solution and chemical activity effects. The transport of water by capillary suction is described by a diffusion equation. In the model, the transport phenomena and the chemical reactions are uncoupled. Phase dissolution and precipitation phenomena are modeled through a separate chemical equilibrium code. The model considers the influence of chemically induced microstructural alterations on the transport properties of the material. A brief description of the model is presented in the first sections of this paper. Typical applications of the model are given in the last section.
Résumé
Ce document présente les principales caractéristiques d’un modèle numérique permettant de prédire le comportement de matériaux cimentaires exposés dans des conditions non saturées à des environements chimiquement agressifs. Le modèle est divisé en quatre parties traitant respectivement du transport d’ions par diffusion, du transport de l’eau, des réactions chimiques et de l’endommagement chimique. La diffusion des ions est décrite en résolvant l’équation de Nernst-Planck étendue. Le modèle prend en considération les effets reliés à l’activité chimique des ions en solution et le couplage électrique entre les différents flux ioniques. Le transport de l’eau par succion capillaire est décrit par une équation de diffusion. Les phénomènes de dissolution/précipitation sont modélisés en utilisant un module d’équilibre chimique. Les effets des réactions chimiques sur la structure poreuse du matériau et ses propriétés de transport sont également considérés. Une brève description du modèle est donnée dans la première partie du document. Des exemples d’application du modèle sont présentés dans la seconde partie.
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Editorial Note Prof. Jacques Marchand presented a lecture of this paper at the 2000 RILEM Annual Meeting in Paris, France, when he was awarded the 2000 Robert L’hermite Medal in recognition of his outstanding contributions to the explanation of corrosion mechanisms in concrete, in particular HPC. Jacques Marchand is a RILEM Senior Member. He works at Laval University (Canada), a Titular Member and is the Chaiman of RILEM TC FHP (“Predicting the frost resistance of high performance concrete exposed to numerous freezing and thawing cycles”). He is also the Secretary of RILEM TC 181-EAS (“Early age shrinkage induced stresses and cracking in cementitious systems”).
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Marchand, J. Modeling the behavior of unsaturated cement systems exposed to aggressive chemical environments. Mat. Struct. 34, 195–200 (2001). https://doi.org/10.1007/BF02480588
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DOI: https://doi.org/10.1007/BF02480588