Abstract
The splitting of concrete covers due to the expansive action of corrosion has been investigated by a finite element method (FEM) based on an element-embedded crack concept called the inner softening band. Fictive cross-sections, with and without transverse reinforcement, were studied. The concrete composition (plain and fibrous high-strength concrete) and the cover thickness were varied. The model produced credible fracturing behaviour in concrete covers and explained the mechanical origin of the cracks. For cover thicknesses less than two times the bar diameter, fibres do not seem to have any significant effect on occurrence of splitting cracks. However, fibres are effective to arrest the opening of arisen splitting cracks and to redistribute the strains to other cracks. Hence, fibres may postpone or prevent a total spalling of concrete covers. A larger cover is necessary not only to prolong the initiation period, but also for the fibres (2 volume-%) to be effective beyond occurrence of corrosion induced cover cracks.
Résumé
La fissuration de la couche protectrice d'une poutre en béton causée par l'expansion due à la corrosion, a été étudiée à l'aide de la méthode des éléments finis basée sur le concept de fissure élémentaire incluse, appelée bande interne de radoucissement. Des sections transversales fictives, avec et sans armatures transversales ont été étudiées. La composition du béton de haute résistance (avec et sans fibres) et l'épaisseur de la couverture des armatures ont été étudiées. Le modèle a généré un comportement crédible de la rupture dans la zone d'enrobage des armatures, permettant d'expliquer l'origine mécanique des fissures. Pour une épaisseur de recouvrement inférieure à deux fois le diamètre de l'armature, les fibres ne semblent pas avoir d'effet significatif sur l'apparition des fissures. Cependant les fibres sont efficaces pour arrêter l'ouverture de fissures existantes et pour redistribuer les contraintes aux autres fissures. Les fibres peuvent retarder ou éviter la destruction de la couche protectrice en béton de la poutre. Une épaisseur de couverture supérieure est nécessaire non seulement pour prolonger la période d'initiation mais aussi pour que les fibres (2% en volume) soient efficaces lors de l'apparition de fissures d'origine corrosive.
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Noghabai, K. FE-Modelling of cover splitting due to corrosion by use of inner softening band. Mat. Struct. 32, 486–491 (1999). https://doi.org/10.1007/BF02481632
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DOI: https://doi.org/10.1007/BF02481632