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Modélisation du transport multi-espèces dans les matériaux cimentaires saturés ou non saturés et éventuellement carbonatés

Abstract : As a part of the IFSTTAR's research project « Performance-based and probabilistic approach to the life cycle of reinforced concrete structures », this thesis focuses on the modelling of coupled ion-moisture transport through concrete which is possibly carbonated. A multi-species modelling platform, based on durability indicators and with different levels of sophistication, was used. In saturated conditions, ion transport was described by the Nernst-Plank equation and complemented by ion-matrix interaction isotherms. In unsaturated conditions, the advection of liquid and gas was described by the extended Darcy law. The influence of the chemical activity on the equilibrium between liquid water and water vapor, as well as the kinetics of the chloride binding, were included. The binding of alkali was also taken into account and its influence on the chloride penetration was investigated. As input data of the models, conventional durability indicators (porosity, intrinsic permeability for liquid water and for gas) were determined by direct measurement on different concretes made of ordinary Portland cement and containing high contents of supplementary cementing materials (fly ash and slag). An inverse method was implemented thanks to a routine which incorporates an optimization algorithm, allowing us to determine some complex properties (such as effective diffusion coefficient, binding isotherm parameters and intrinsic permeability to liquid water) from experimental results. The model for saturated conditions was validated by comparing the simulation results to experimental profiles obtained from chloride diffusion tests. Wetting tests, with saline solution or pure water followed by drying experiments, on sound concrete and possibly carbonated ones were led to verify the model for unsaturated conditions, as well as to highlight the influence of carbonation on the ion and moisture transport.In addition to a further understanding on the physico-chemical mechanisms related to the durability of concrete and the identification of durability indicators by inverse analysis, the platform allowed us to predict the transport of ions and moisture according to the complexity of the involved phenomena and the required level of sophistication. The relevance and the reliability of the modeling platform for transport were proved by the studies carried out
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Xiaomeng Wang. Modélisation du transport multi-espèces dans les matériaux cimentaires saturés ou non saturés et éventuellement carbonatés. Autre. Université Paris-Est, 2012. Français. ⟨NNT : 2012PEST1037⟩. ⟨tel-00730834⟩

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