Abstract
In structural elements consisting of concretes of different ages (hybrid elements), hygral deformations induced by drying of the new concrete are restrained by the old concrete. Depending on the amplitude of these deformations and on the degree of restraint of the hybrid element, cracks can be induced in the new concrete layer. An experimental investigation conducted during six months on twelve hybrid elements demonstrated that global displacements are reduced when the reinforcement ratio placed in the new layer is increased. Comparison of the experimental results with a numerical model shows that the presence of reinforcement in the new layer increases the degree of restraint of hygral deformations and the likelihood of localized cracks.
Résumé
Dans les éléments de structure formés de bétons d’âges différents (éléments hybrides), les déformations induites par le séchage de la nouvelle couche sont entravées par le support de vieux béton. En fonction de l’amplitude de ces déformations et du degré d’entrave de la structure hybride, des fissures peuvent être induites dans la nouvelle couche. Des essais de fluage flexionnel réalisés durant six mois sur douze éléments de structure hybride ont permis de mettre en évidence que leurs déplacements induits par le séchage de la nouvelle couche sont réduits lorsque le taux d’armature placé dans cette couche augmente. En s’appuyant sur les résultats obtenus lors de la validation de la modélisation numérique proposée, cet article démontre que la présence de barres d’armature dans la nouvelle couche augmente l’entrave de ses déformations de séchage et favorise l’apparition de fissures.
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Editorial Note Prof. Eugen Brühwiler is a RILEM Senior Member. He works at EPFL, a RILEM Titular Member and participates as a corresponding member in RILEM TC 189-NEC ‘Non-destructive evaluation of the “covercrete” (concrete cover)’.
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Bernard, O., Brühwiler, E. The effect of reinforcement in the new layer on hygral cracking in hybrid structural elements. Mat. Struct. 36, 118–126 (2003). https://doi.org/10.1007/BF02479525
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DOI: https://doi.org/10.1007/BF02479525