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Modélisation du comportement mécanique du béton par approche multi-physique (couplage chimie-mécanique) : application à la réaction alcali-silice

Abstract : Alkali-silica reaction is a pathology of concrete which induces irreversible damage for various types of structures (bridges, dams, pavements, etc.). It is a chemical reaction which occurs between the alkalis in cement paste and the silica present in some of the aggregates used for concrete preparation. Although some recommendations exist to prevent the development of this pathology, numerical modeling of the effects of alkali-silica reaction on mechanical properties of concrete remains an important issue for civil engineering applications. This thesis thus aims at advancing in the understanding and modelling of chemical and mechanical processes, and their interactions during the ASR. In a first stage, a model has been developed in order to cope with the chemical modeling of the alkali-silica reaction. This model is a coupled model dealing with two main variables – namely the concentrations in alkalis and silica. It provides at any time of the reaction and at every location of the sample the concentrations of the different species. The kinetics of the reaction is also taken into account through a parameter - the kinetics constant - which may be identified numerically. In order to couple chemistry and mechanics, this model has been implemented in the numerical tool FEMCAM (Finite Element Model for Concrete Analysis Method) - which simulates the 3D mechanical behavior of quasi-brittle materials - such as concrete. A mesoscopic approach has been used here and concrete is considered as a two-phase material composed of aggregates embedded in a mortar paste. A non local Mazars model - with implicit formulation – has been implemented in this tool in order to describe the elastic damage behaviour of mortar paste, aggregates are considered as having a purely elastic behaviour. The chemical model has then been coupled to the mechanical model in order to consider the effects of the ASR on the concrete's behaviour. A granular swelling has been considered in which the aggregates themselves swell within the mortar paste - and not the gel formed by the reaction. The inverse coupling - that is to say, the influence of concrete's mechanical degradation on the reaction's progress - has also been modelled by a simple but easily scalable law. The complete model has been validated thanks to different experimental campaigns, numerous sensitivity studies have been carried out to understand better the influence of the various parameters involved in the reaction.
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Submitted on : Friday, May 7, 2010 - 11:30:54 AM
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  • HAL Id : tel-00481739, version 1

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Raphaëlle Naar. Modélisation du comportement mécanique du béton par approche multi-physique (couplage chimie-mécanique) : application à la réaction alcali-silice. Mécanique [physics.med-ph]. École Nationale Supérieure des Mines de Paris, 2009. Français. ⟨tel-00481739⟩

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