A mesoscopic approach for a better understanding of the transition from diffuse damage to localized damage

La Borderie, C., Lawrence, C., N'Guyen, T.D. & Nahas, G. (2010), "A mesoscopic approach for a better understanding of the transition from diffuse damage to localized damage", In Fracture Mechanics on Concrete and Concrete Structures, FraMCoS'7. Jeju, KOREA. 23-28 May 2010.

The aim of this paper is to present a modeling of mechanical behavior of concrete at a mesoscopic scale, in 2 and 3 dimensions. Concrete is considered as a bi-phasic material where the cement paste and the aggregates are described with their own mechanical characteristics. The aggregates are idealized with circular shapes (discs in 2D, spheres in 3D). The aggregates are randomly placed into the concrete specimen, conforming to the aggregates size distribution curve and the aggregate / paste area ratio. In a first time, the model is studied in two dimensions in order to optimize the geometrical model of the inner structure of concrete in terms of the meshing strategy and the smallest size of the aggregate to take into account. An original method to mesh the mesoscopic geometry of concrete has been developed with diffuse mesh, and the results of the 2D model are analyzed and compared in tension and compression. A first interesting result is that the model can exhibit dilatancy of concrete in compression even when a simple damage model (without plasticity nor inelastic strains) is used. The model shows as well interesting results on the transition from diffuse to localized damage. Finally, results of the tridimensional model are shown in tension.