Fractal dimensions of cement-based composites after mechanical comminution

The paper reports about the comminution of cementitious composites in a laboratory jaw breaker. Two samples of cement paste, one mortar sample, one lightweight concrete sample, and samples of four standard concrete mixtures were investigated. Water–cement ratio and maximum aggregate size were varied. Based on sieve analysis, the fractal dimensions of the fragment samples were estimated. The fractal dimensions varied in a range between DF = 1.90 and 2.22, whereas the lower value belonged to the mortar specimen. Materials with failed through a single, dominant fracture propagation mode could be approximated suitably with a one-parameter fractal model. Other mixtures could better be modelled with a bi-linear procedure.

► Systematic SEM inspections are combined with fragment size analysis.
► Fragments show features of non-linear crack propagation.
► The fractal dimensions of the fragments range between 1.90 and 2.22.
► Materials which failed through multiple fracture modes showed by bi-fractality.