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Abstract: We propose an analytical and numerical study of the combined action of the thermodiffusion and the convection in a binary mixture. The combination of these two phenomena is called thermogravitational diffusion. We are interested in quantifying the separation in a horizontal parallelepipedic cavity filled with a binary mixture and subjected to a constant horizontal temperature gradient on the two horizontal walls, the other walls being thermally insulated and impermeable. This new procedure is different from the classical one where the cavity is vertical and differentially heated on the two vertical walls. To cite this article: B. Elhajjar et al., C. R. Mecanique 334 (2006). [Copyright &y& Elsevier]

The prediction of concrete strength has become a major concern that is forcing the construction industry to look closely at determining the appropriate time when to strip the form work or to apply prestress forces to new concrete. Normal concrete has different constitutions and can be subjected to different curing methods depending on the means available. Its characteristics are defined by the presence of mineral additives used to improve its efficiency. This has led us to establish a work plan to predict the strength of slag concrete, tested at different temperatures, from the data obtained from some control specimens of normal concrete, made only from clinker and subjected to a constant temperature of 20°C. The slag material was obtained from El-Hadjar (Algeria).Key words: slag, activation, temperature, finesse, thermal treatment, prediction, equivalent time, mortar, compression, cement, additives.La prévision de la résistance des bétons d'aujourd'hui est devenue une préoccupation majeure poussant les promoteurs de la construction à s'y intéresser de plus en plus pour prévoir le décoffrage ou la mise en précontrainte à un âge approprié. Les bétons actuels possèdent une composition différente des bétons d'hier caractérisée par la présence de certains ajouts minéraux pour améliorer ses performances et un mode de cure variant selon les moyens disponibles. Ceci nous a conduit à établir un organigramme de prévision de la résistance en compression des bétons au laitier d'El-Hadjar subissant un historique de température variable, à partir d'un béton de référence confectionné uniquement avec du clinker et conservé sous une température constante de 20°C.Mots clés : laitier, activation, température, finesse, traitement thermique, prévision, temps équivalent, mortier, compression, ciment, ajouts. [ABSTRACT FROM AUTHOR]

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