Abstract The results from investigations on the physical and mechanical properties of cement mortars and concretes containing the active mineral Pozzolit admixture are presented in this paper. The basic components of this admixture are silica fume (SF) and low calcium content fly ash (FA). The compressive and flexural strength and modulus of elasticity of cement mortars and concretes containing Pozzolit have been determined as well as the water- and gas permeability. The results have been compared with corresponding parameters of cement mortars and concretes without mineral admixture or with only one component — either silica fume or fly ash. It has been established that the Pozzolit active mineral admixture contributes not only to overcome the technological difficulties encountered in the process of silica fume delivery in cement mortars and concretes but also to improve cement stone strength and resistance.