Filip Nilenius

A 3D/2D Comparison between Heterogeneous Mesoscale Models of Concrete

A model for 3D Statistical Volume Elements (SVEs) of mesoscale concrete is presented and employed in the context of computational homogenization. The model is based on voxelization where the SVE is subdivided into a number of voxels (cubes) which are treated as solid finite elements. The homogenized response is compared between 3D and 2D SVEs to study how the third spatial dimension influence the over-all results. The computational results show that the effective diffusivity of the 3D model is about 1.4 times that of the 2D model.

FE2 Method for Coupled Transient Diffusion Phenomena in Concrete

A coupled finite-element squared (FE²)-framework is formulated and employed for simulation of a transient and coupled moisture-chloride ion diffusion problem in concrete. Simulations are carried out on the macroscale, where the material response is obtained concurrently in the computations by introducing a representative volume element (RVE) in the macroscale quadrature points. The RVE, in turn, contains the mesoscale heterogeneities of concrete in terms of cement paste, aggregates, and interfacial transition zone (ITZ). In this fashion, the RVE comes to serve as a constitutive model for the macroscale. A numerical example is given to show how the transient macroscale diffusion is influenced by the composition of the mesoscale constituents. Parametric studies were carried out with respect to the aggregate content within the RVE, both including and excluding the ITZ, and the coupling parameters of moisture and chloride ions.