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Drying behavior of concrete : application to nuclear waste packages

Abstract : EDF is currently working on multiple projects concerning the durability of concrete structures. Among these projects, a research program focuses in particular on the drying behavior of a high performance concrete used as a shell for nuclear waste packages. The package of interest noted as C1PGSP, will be at first conserved in a storage facility and then disposed of at Cigéo, i.e. the future underground disposal facility for long term radioactive waste in France.During the storage phase, the “F44Adj” concrete shells will be submitted to relative humidity that could be lower than 50% and a relatively high ambient temperature (attaining 50°C). Under these conditions, the impact of drying has to be evaluated and EDF is required to verify the package against the risk of cracking of the concrete shell due to structural restraining of strains.The overall objective of this thesis is to provide a new valid poromechanical model that can be used to study the risk of cracking of the concrete shell caused by the restriction of drying shrinkage.Previous modelling works based on a classical Thermo-Hydro-Mechanical (THM) formalism have shown the need of a better understanding of the drying behavior of concrete, in particular to what concerns the hydromechanical coupling. As a matter of fact, the THM models based on the poromechanical works of Biot, Terzaghi and then Coussy et al. (2003), are proven to be only valid for a relative humidity higher than 50% (Wyrzykowski et al., 2017). In this thesis, we propose a new poromechanical model that extends and adapts those models to a lower relative humidity. This result is obtained by introducing the mechanism of adsorption of water molecules on the pores surface and its effect on the hydro-mechanical coupling.Apart from the hydromechanical coupling, the drying kinetics of the concrete impacts the kinetics of shrinkage. The existing models of water transfer are examined and discussed with respect to their applicability to high performance concretes (such as the F44Adj). Hence, two chapters of this thesis are devoted to the water retention phenomenon and to the transfer properties of the concrete.Finally, material properties are necessary to correctly model the drying behavior of the F44Adj concrete. For this reason, EDF has established an experimental program in order to obtain the data necessary to calibrate the transfer parameters as well as to validate the proposed poromechanical model. Hence, a large section of each chapter is dedicated to the description and analysis of experimental results, then to calibration of the model parameters.The proposed model is finally applied to simulate the drying of the C1PGSP package under storage conditions; results are compared with those obtained in older simulations performed at EDF.
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Submitted on : Wednesday, November 3, 2021 - 4:00:28 PM
Last modification on : Friday, November 5, 2021 - 3:24:30 AM

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  • HAL Id : tel-03413178, version 1

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Ginger El Tabbal. Drying behavior of concrete : application to nuclear waste packages. Mechanics of materials [physics.class-ph]. Université Paris-Est, 2020. English. ⟨NNT : 2020PESC1016⟩. ⟨tel-03413178⟩

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