Clinker is the basis component of Portland cement, which participate in forming of the strength structure of the binder matrix. Clinker storage in improper conditions may have as consequence modification of its characteristics and implicitly, of the cement preformaces. The work follows storage influence in uncover stockpiles of clinker and granulated furnace slag on their characteristics and on the performances of a cement type CEM II/A-S with 20% granulated furnace slag. In this way, at different periods, chemical and mineralogical investigations (X-ray diffraction, optical microscopy) are carried out. Also, hydraulic activity influence of the clinker and granulated furnace slag on physical-mechanical characteristics of the cement is presented.