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Over the past decades a considerable research effort has been attributed to the modelling of chloride ingress into reinforced concrete in order to predict its durability. Traditional models are based on the error-function. In the present paper computational results of an advanced model are presented, which takes environmental temperature and humidity fluctuations, chloride binding, diffusion and convection, as well as carbonation effects into account. These qualifications make the model particularly suitable for simulating drying-wetting cycles, an example of which is included. The good performance of the moisture sub-model is demonstrated in an example concerning drying cement paste. Another example deals with a simple submersion case. The examples are based on laboratory and real-life experiments with documented concrete or paste compositions and environmental conditions, as well as the eventual measured chloride profiles. In general, the computational results are in good agreement with the measurements. The paper concludes with a comparison between simulation results of the present model and the error-function model for the case of cyclic drying-wetting exposure. It appeared that the implicit negligence of the moisture fluctuations by the error-function model, forced that model to deploy strongly deviating material characteristics to reach agreement with the measured chloride profile.1359-5997 9 2004 RILEM. All rights reserved. RESUMg Pendant les dernibres dEeennies un effort de recherche considerable a EtE attribuE gl la modElisation de la pEnEtration des chlorures dans le bEton armE pour prdvoir sa durabilitO. Les modbles traditionnels sont fondEs sur la fonction d'erreur (erJ). Dans cet article sont presentEs plusieurs rEsultats numEriques issus dun module avancE, qui tient compte des fluctuations de temperature et d'humiditE du milieu, de la liaison, diffusion et convection des

* Delft university of technology, faculty of civil engineering and geosciences, materials science group ** Delft university of technology, Koiter institute / faculty of aerospace engineering Exposure to a saline environment is a major threat with respect to the durability of reinforced concrete structures. The chloride ions, which are present in seawater and de-icing salts, are able to penetrate the concrete up to the depth of the reinforcement. They can eventually trigger a pitting corrosion process. The assessment of a corrosion-free service life of concrete structures is of paramount economic interest. However, the modelling of the ingress of chloride ions is complicated due to various influencing factors and transport mechanisms. Here a computational model for chloride ion transport through a porous material is presented. Chloride ion transport in rein- Key words: chloride penetration, reinforced concrete, corrosion, coupled transport, porous media IntroductionThe design of concrete structures involves mainly the evaluation of strength, stability and durability. A major threat to concrete durability is chloride. As chlorides are present in salty water and deicing salts, special care has to be taken in the design of off-shore structures, bridges and parking garages. Also buildings in coastal areas are subjected to chloride ion ingress. The deterioration mechanism is the following: chloride ions penetrate the concrete to the level of the reinforcement, when they are in a sufficient quantity they depassivate the rebars, pitting corrosion starts if also oxygen is available, the effective cross section of the rebars decreases and cracks appear due to the expansion of rust products. The cracks and the decrease of the effective cross section of the reinforcing steel bars imply a strength loss, while the cracks also enhance the deterioration process.Chloride ion ingress in reinforced concrete has been subject of research for many decades and tra- HERON, Vol. 46, No.3 (2001) ISSN 0046-7316 207 ditionally this process has been modelled by Fick's second law. The only material parameter in this model is the effective chloride diffusion coefficient. The adjective "effective" already suggests that many effects are hidden in this coefficient. Very few attempts have been made to substantially refine the modelling, e.g. by [Saetta 1993]. With the aid of current computing techniques, complex problems can be solved which could not be handled in the time the effective diffusion approach was proposed. Here a refined approach is presented based on the interaction of three simultaneous processes: chloride ion transport, moisture migration and heat flow. The model also takes into account the inhomogeneous character of concrete on the meso-level. Three components are distinguished:mortar, aggregates and interfacial transition zones. Model structure 208The distance from the concrete surface to the reinforcement bars amounts to a few centimeters approximately. This is the distance which the chloride ions have to travel before they ...

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