Abstract
	The CaO pellets were prepared from powdered limestone by cold pressing and one-stage burning at temperatures of 1550°C and 1600°C, respectively. The effect of pressure ( 20 - 200 MPa) and amount of added water (0 - 3 %) to powdered limestone Gombasek on bulk density, apparent porosity, volume shrinkage at burning temperature of 1550°C as well as effect of impurities and genesis of various limestones (Gombasek, Hosťovce, Trzuskawica) on CaO densifying and structure at higher temperature of 1600°C were studied in this work. Achieved results reveal that for the sufficient quality of the burned CaO the pressure of 20 MPa is an optimum as well as amount of added water equal to 0 - 1 %. This water serves as a lubricant. Such amount of water represents the natural content of adsorbed water in powderd limestone. At burning temperature 1600°C the following bulk densities were achieved: 2,97 g.cm-3 for CaO Hosťovce (where the content of impurities is 5 %) and 2,69 g.cm-3 for material Trzuskawica (impurities content 0,5 %). The bulk density of CaO from Gombasek was similar to CaO from Hosťovce. Above mentioned materials have similar impurities content and also their genesis is indentical. The observation of individul microstructures of materials indicates that both of CaO materials from Gombasek and Hosťovce have similar developed structure after burning in contrast to the weakly developed structure with small crystal size of CaO from Trzuskawica. It can be said that densifying process is affected not only by the impurities but also by the genesis of limestones. Concerning to the hydration rate in humid environment very pure CaO clinker from Trzuskawica goes under hydration (21°C - 74 %) very rapidly because of lowest bulk density and high apparent porosity values.