A three dimensional numerical model for the composite structure of concrete is proposed. Ag- gregates are embedded in a mortar matrix. The Interfacial Transition Zone ( ITZ) between matrix and aggre- gates is also taken into consideration as a third…
A three dimensional numerical model for the composite structure of concrete is proposed. Ag- gregates are embedded in a mortar matrix. The Interfacial Transition Zone ( ITZ) between matrix and aggre- gates is also taken into consideration as a third phase. A finite element mesh generation of this model is real- ised by tetrahedral elements based on Delaunay triangulation. The aggregates, following a predefined size distribution, are placed randomly in the specimen. An increase of the aggregate concentration is possible but at the expense of the topological quality of the numerical model. The shape of the aggregates is approximated by spheres or ellipsoids. The matrix , consisting of mortar with a maximum grain-size of 2 mm, is assumed to be homogeneous with effective material parameters. The interface layer surrounding the aggregates repre- sents a weak zone and can be assigned with statistically distributed material properties. Finite elements with linear or quadratic interpolation functions are considered. By means of this numerical model the effective properties and behaviour of the composite structure, e.g. the effective Poisson's ratio, are studied as function of parameters of its components. Furthermore time-dependent phenomena such as drying and stresses induced by hygral variations are simulated. The implementation of non-linear material laws and the smeared crack model enable the calculation of damage and crack formation in the specimen. As a final step the mechanical behaviour under coupled, external mechanical and hygral stresses is mentioned.