Particle packing in a model concrete at different levels of the microstructure: Evidence of an intrinsic patchy nature

Microscopical observations have revealed the physical existence of a so-called patch microstructure in concrete. This paper presents evidence that this patchy nature also extends to a meso-level. Physical discrete element modeling (DEM) by a concurrent algorithm-based system is used for this purpose. This DEM approach constitutes an economic, efficient and potentially reliable option for investigating the non-uniformities in the distribution of aggregate grains and fibers on a meso-level, or of the unhydrated cement nuclei or pores in a matured cement paste on a micro-level. The observed patchy nature at different levels of the microstructure is in agreement with theoretical expectations based on the natural concept of a Poisson process.