The object of the research is activated mineral fillers used for modification of cement composites. Modification with activated fillers of cement composites provides an opportunity to increase the level of strength indicators of road-building material, as well as to reduce the content of the main binder. Dolomite was used as a mineral filler. Mechanical activation of the fillers was carried out in the Vortex 297 vortex apparatus, with different exposure times. To ensure effective activation, the optimum filling factor of the grinding chamber and the size of ferromagnetic particles were determined. The character of dispersion distribution of mineral filler particles on the laser analyzer depending on the activation time was studied. The state of surfaces of a mineral filler after activation is estimated by method of acid-base interactions with definition of free surface energy which level of indicators characterizes ability of a surface to interphase interaction. Influence of activation time and mineral filler content on compressive strength of cement stone samples was established. The optimum time of activation of mineral filler in the vortex layer apparatus was determined.