The influence two composition of CS containing as crystalline phase mullite or quartz for production concrete was studied. The pozzolanic activity of CS (Q) significantly depend on dispersion and treatment time in Ca(OH)2 solution. Due to high content of amorphous SiO2, the specific character of crystalline structure of mullite and structural collapse (increase amounts of reactive Al2O3) after 14 days treatment of M specimens, a sharp increase in activity of spheres exceeded an activity of fine-grained particles. On the surface of CS (M) and broken areas, formation of amorphous white deposits and crystalline phase - calcium aluminate has been observed. CS (Q) pattern remains without significant changes on the surface of the sphere. Investigation behaviour of CS in cement paste showed pozzolanic activity of mullite containing CS and inactive character of crystalline quartz containing CS. Investigated CS dependent on chemical composition can be recommended both as reinforcing filler (crystalline quartz containing) and pozzolanic additive (mullite containing) in cement paste structure.