Influence of microstructure of concrete on size/scale effects in tensile fracture

Size/scale effects on the fracture of concrete subjected to uniaxial tension are studied by means of analyses with the Delft lattice beam model and compared to recent experimental results. Using a simple local elastic–purely brittle material global softening behaviour is calculated. The effect of deterministic and statistical contributions to size effect is studied by implementing different degrees of heterogeneity to the lattices. They vary from ‘homogeneous’ regular triangular lattices to lattices with randomly varying beam length. Computer generated particle overlays are used to improve resemblance to real concretes. Trends in size effect on nominal strength and fracture energy are in close agreement with the experiments. The type of approach can be used for tuning macroscopic size/scale laws for concrete and related materials.