Review article

The article presents the results of the research aimed at identifying the influence of the aggregate on the plasticity of concrete mixtures used in formless molding. The authors provide a brief overview of the existing concepts regarding the effect of the aggregate on the rheology of mixtures and their plastic properties. There is offered a description of the materials and techniques used, as well as the experiment and analysis of the results obtained. There have been experimentally established two mechanisms of the influence of the aggregate on the plasticity of the concrete mixture. Due to the sorption of water from the cement paste, the aggregate, at any of its volumetric concentrations, reduces its ultimate tensibility and, as a consequence, the plasticity of the entire mixture. When the volume fraction of 41 % is exceeded, the aggregate also depletes the sufficiently plastic component of the mixture - cement paste - thereby reducing the ultimate tensibility of the mixture, which enhances the effect of drying the paste.