This article discusses a nano-modifying additive in concrete, obtained by mechanical activation of the initial components of a fine-grained concrete mixture. Mechanical activation of a cement-sand mixture of a certain granulometry was carried out in an energy-saturated ball mill under a given activation mode. The indicators of dispersion of the resulting composition are determined. The activated cement-sand composition was introduced into the compositions of fine-grained concrete instead of 5% and 10% cement by weight. The rheological parameters of freshly prepared mixtures were determined, it was shown that in these amounts the additive does not significantly affect the flowability and density of the mixture. There is a reduction in the start time of setting, while the end time of setting in mixtures with additives increases. Thus, by partial activation of the initial components, it becomes possible to regulate the setting time depending on the required indicators. It has been experimentally proved that the mechanical activation of the initial components of the mixture affects the strength in the first days of concrete hardening. Mechanical activation contributes to the disclosure of the unused potential of the initial components of the fine-grained concrete mix. An active mineral additive obtained by mechanical activation of a cement-sand composition can become an alternative to expensive additives, especially when using regional raw materials for its production.