As natural resources of sand and fine material used in the concrete industry are becoming more scarce, crushed materials are being used to a greater extent. Shape and texture of machine crushed materials differ from aggregates naturally ground, layered and sorted under the course of millions of years. It is assumed that crushed aggregates are more angular and of less smooth texture than natural aggregates, which will affect the flow behaviour of a suspension containing crushed material. In the mix design process of cementitous suspensions, an adequate rheology of the micro mortar (all constituents in the concrete being able to pass a 0.125 mm sieve, including the cement) is crucial. In this paper, the shape of fine particles is linked to the micro mortar plastic viscosity of the filler suspension including cement. The plastic viscosity here serves as an important quality assessment of the filler, since the micro mortar workability features are vital for the final mix design quality of the concrete workability.