Abstract: The study gives consideration to the influence of characteristic properties of chemical and mineralogical composition and structure of blastfurnace slag on artificial brick physical and mechanical properties formation of during hard firing. The researchers have examined blastfurnace slags with variety of compositions and structures and have found out the peculiarities of heating structure formation depending on the type of additive. The results of experimental work analysis show that the temperature and range of sintering of the materials under consideration having high concentration of alkaline-earth oxides (CaO, MgO) depend both on the total content of such oxides in a raw mixture and on the phase state of their compounds as well as on the type of structure of a slag component.