Influence of internal dilation on the fracture behaviour of multi-phase materials

Numerical modelling on the micro- and meso-level of concrete is presented. The formation of the microstructure, including the matrix and the interfacial transition zones between aggregate particles is modelled explicitly on the micro-level. The outcome of these simulations are used in a meso-level model (lattice model) to study the formation of (micro-)cracking in concrete consisting of particles embedded in a matrix. The different matrix and interface properties as well as the level of restraining of deformations is included in these simulations. Three concrete mixes with different water–cement ratio are investigated. A lower w/c shows more autogenous shrinkage, higher eigenstresses and thus a higher tendency for cracking. From the simulations it is found that eigenstresses caused by autogenous shrinkage reduce the tensile strength of the concrete. However, it is also concluded that the local material properties are very important and influence the outcome of the simulations to a large extent. Furthermore, the influence of microcracking or weak zones on the ductility of multi-phase materials is investigated. It is found that the ratio between the strengths of the components in a material determines the width of the fracture process zone and also the ductility of the material.