Calcareous gaize, a rock with a high content of detrital quartz, silica and calcite, belongs to the group ot sedimentary rocks of marine origin.In Poland, the deposits are located in the north-eastern edge of the (S)wi(e)tokrzyskie Mountains, Roztocze area (chalk) and Lublin Upland (tertiary).The studies to date suggest that it may be a valuable addition for the production of Portland cement.There is a lack of studies on the influence of Geza hydration processes of pure Portland clinker phases in the literature so far.Dispersed calcium carbonate,present in gaize, reacts with C3A to form sulfate resistant C3A·CaCOy 12H2O phase, calcite activates the hydration of alite and active silica absorbs Ca(OH)2.The research will be carried out in the C3A-Gaize-CaSO4-H2O system to determine whether only ettringite and carboaluminate is formed, or if there is a possibility of a formation of a solid solution of those two phases.The examinations will be carried out under normal curing conditions and hydrothermal conditions.In order to monitor the hydration process SEM(EDS),XRD, DTA/TG, conductometry and microcalorimetry laboratory techniques have been used.