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Theses

Modeling tools for concrete casting

Abstract : Thanks to the recent advances in the cementitious materials rheology field, existing works allows for the physical quantification of workability of fresh concrete. The objective of this thesis is to develop techniques allowing for the prediction of casting according to these rheological measurements, the geometry of the element to be cast and the selected casting process. The methodology adopted is to isolate and treat each of the involved phenomena in a simpler configuration and then to gradually combine them ail. A simple model material able to reproduce the main features of the rheological behavior of concrete was first developed on the basis of glass beads of uniform diameter and roughness controlled mixed in a suspension of Carbopol (stable, transparent and non-thixotropic yield stress fluid). A series of tests with the model material in a bounded horizontal channel with or without steel bars allows for the following studies: The flow stoppage of the material as a function of its yield stress and the geometrical characteristics of the formwork; the flow stoppage as a function of the obstacles such as the steel bars; the particle jamming into the steel bars. These laboratory tests have been carried out in conjunction with analytical approaches and numerical simulations. A correlation analysis between the rheological properties of the material and the flow stoppage is proposed and compared with numerical simulations and experimental measurements. ln addition, a probabilistic approach able to predict the jamming of the coarsest particles into the steel bars according to basic variables such as the size of the grains, their concentration, the volume of material and the geometrical characteristics of the steel bars is proposed and validated in the case of real concrete. However, it is shown in the light of the extrapolated computation time that the numerical simulations used in this thesis and taking into account each of steel bars can not be considered as an engineering tool usable in practice. An analogy between reinforced zone and porous media is then proposed. 1t consists in considering con crete casting as the flow of a yield stress fluid into an anisotropic 'heterogeneous porous medium. 1t becomes thus possible to transform a given map of steel reinforcement into a map ofpermeability. This technique has been validated in the case of simple flows of real concrete in laboratory formwork.
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Submitted on : Monday, August 18, 2008 - 8:00:00 AM
Last modification on : Monday, August 18, 2008 - 8:00:00 AM
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  • HAL Id : pastel-00004048, version 1

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Thi Lien Huong Nguyen. Modeling tools for concrete casting. Engineering Sciences [physics]. Ecole des Ponts ParisTech, 2007. English. ⟨pastel-00004048⟩

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