Méthode d'étude mécanique et physico-chimique de l'interface acier-béton

Résumé

Cet article présente un modèle expérimental permettant de relier l'adhérence entre acier et béton aux caractéristiques physico-chimiques de la liaison et de suivre l'évolution de ces caractéristiques au cours d'actions endogènes et exogènes. L'étude théorique du modèle constituté de deux matrices de mortier séparées par une plaque d'acier, fait apparaître un champ de contraintes relativement complexe à l'interface. L'étude expérimentale sur une éprouvette instrumentée confirme la complexité du champ de déformation au voisinage de l'interface et permet la comparaison avec l'approche théorique. Les premiers résultats concernant des éprouvettes fabriquées à partir de plaques d'acier présentant divers états de surface (oxydé, non-oxydé, galvanisé) permettent de coupler les deux types d'investigation: mécanique et physico-chimique.

Summary

Steel-concrete bonding is a major factor in the durability of reinforced concrete. Much research has been devoted to steel-concrete bonding with regard to mechanical or to physical and chemical characteristics, but so far no studies of the interface have involved both kinds of investigation.

Thus, research was started to link the steel-concrete bond with physical and chemical observations, following the development of the bond in response to endogenous or exogenous mechanical and physico-chemical effects. An experimental model is used comprising two pieces of mortar separated by a steel plate and subjected to compressive tests.

In the first part, this paper deals with a theoretical study of the strain and stress fields at the steel-mortar interface of the model. Three plate orientations are studied(30, 45, 60°). The stress field seems complex, but nevertheless for one orientation the shear stress field is almost constant. Experimental study by means of a test piece provided with strain gauges confirms the complexity of the strain field in the neighbourhood of the interface, but allows a comparison with the theoretical results.

In the second part, this paper gives results for specimens made with different steel plates (galvanised, corroded, non-corroded). After failure of specimens, the interfaces have been analysed by X-ray diffraction and scanning electron microscopy. Correlations between the two kinds of investigation were established.