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Influence de la température et de l'hygrométrie sur le comportement instantané du béton

Abstract : In case of severe accident, confinement chambers are submitted to thermodynamic variations of their internal environment. Pressures can increase up to 5 bars, temperature reaches 140 °C and relative humidity attains saturation. Beyond regulatory calculations, the complexity of the solicitation needs a good knowledge of the thermo-mechanical behaviour of concrete under the imposed conditions of temperature and relative humidity. This, in turns allows to develop numerical simulations as realistic as possible. The present study investigates the evolution of the mechanical and thermal characteristics of concrete. These properties are essential to develop numerical computations under the levels of pressure, temperature and relative humidity imposed during a severe accident. Mechanical and thermal tests are carried out under controlled hydro-thermal conditions. Temperature (T) is fixed at five target values: 30, 90, 110, 140 and 160 °C. Five levels of degree of saturation (Sw) range from 36 % to 100 %. The different target values of degree of saturation are attained by controlling relative humidity in the surrounding environment of the specimens during curing. DCT (Disk-shape Compact tension) tests was chosen to determine the dependence of the fracture energy, elastic modulus and traction resistance on temperature and degree of saturation of concrete because of its compact shape that is more suitable for testing under pressure (temperature above 100°C). Thermal properties are determined by means of the Transient Plane Source (TPS) method. This technique allows to determine thermal conductivity, thermal diffusivity and hence to deduct specific heat. The dependence of the permeability to liquid nitrogen on temperature up to 90 °C and on the degree of saturation was also analysed. After determining thermal and mechanical properties of concrete, numerical simulations have been developed in order to pass from laboratory scale to the structure scale. A coupled hydro-mechanical model and a damage model are proposed.
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Submitted on : Monday, November 18, 2019 - 9:42:42 AM
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Hatem Kallel. Influence de la température et de l'hygrométrie sur le comportement instantané du béton. Mécanique des matériaux [physics.class-ph]. Université de Pau et des Pays de l'Adour - Laboratoire SIAME, 2016. Français. ⟨tel-02367577⟩

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