The purpose of the present research is to evaluate the possibility of using montmorillonite mineral nano particles (MNP) as active additives in concrete compositions in order to improve mechanical characteristics of concrete. This paper presents the results of the experimental study carried out with the aim to evaluate basic mechanical properties and long-term creep deformations of the developed concrete composition. Concrete specimens have been tested at a constant room temperature and with a constant level of moisture and properties of the concrete have been examined. The results of the experiments demonstrating the relationship of the stress and strain have been presented. The compression strength, the modulus of elasticity, the creep and creep coefficient of the concrete specimens have been determined.