SCC flow curves from vane geometry rheometer

International audienceThe objective of the present study is to show how recording the changes in the rotation torque according to the rotation speed can lead to identifying a characteristic flow curve for the tested concrete. The concrete rheometer used for the study is composed of a vane tool. The rotation speed of the tool is imposed and the resulting torques are measured. The experimental rotation protocol used in this study corresponds to a rapid speed increase followed by a steady speed then the rotation speed slows down. The evolution of the torque measured as the rotation speed decrease (restructuring phase) is considered as being a succession of stationary states. By considering the fluid equivalent to a Bingham fluid for which the yield stress has already been identified and by using an analogy with a coaxial-cylinders rheometer, relevant relationships between the rotation speed of the vane and the rate of shearing along the tool are identified. Shear stress and shear rate calculations for each value of torque and rotation speed lead to the complete flow curve of the tested fluid. The data treatment method is adjusted to accurately evaluate the parameter linked to the flow stop in the case of a non-nil shear rate when the yield stress is reached. The comparison of the characteristic rheological parameters of SCC obtained from the rheometer and both spreading and V-Funnel tests indicate very satisfactory correlations

La mécanique du sable mouillé

Extrait de documentA model for mechanical behaviour of saturated granular media is proposed. Some elementary notions (friction, cohesion...) are presented and the interactions between granular structure of media and the interstitial fluid are analysed and illustrated. Presentation of different results obtained under various experimental conditions, with oedometric and triaxial testes, permit the progressive development of a behaviour model. This simple model allows the understanding of the relation between dilating-contracting character of the material, the initial state of sample and evolution of its stress state.Une modélisation du comportement mécanique des milieux granulaires saturés est proposée. Quelques notions élémentaires (frottement, cohésion...) sont rappelées et les interactions entre l'ossature granulaire du milieu et le fluide interstitiel sont analysées et illustrées. La présentation des différents résultats obtenus dans des conditions expérimentales variées, à l'aide des essais odométrique et triaxial, sert à la construction progressive d'un modèle de comportement. Ce modèle simple permet de comprendre les relations entre le caractère dilatant-contractant du matériau, I'état initial de l'échantillon et l'évolution de son état de contrainte

New Italian directional and intensity archaeomagnetic reference curves for the past 3000 years: Insights on secular variation and implications on dating

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