ИСТИНА

Usually to obtain expansive cements sulphoaluminate clinker or mix aluminate clinker with calcium sulphates (gypsum, hemihydrate, anhydrate) are used. For these cements ettringite is an important hydration product and reaction kinetics of this phase plays an important role in determinаting performance. The alternative aluminate phases may be ferrite containing ones. This paper deals with the composition and properties of solid solution of calcium sulphoaluminate, sulphoferrite and sulphoaluminoferrite cements. It was studied an influence of calcium sulphate on structure and properties of calcium aluminate and ferrite phases, and their stability under high temperatures. Beside that the properties of cements containing these phases were studied. The investigation of hydration and properties of sulphomineral cements shows that ettringite and its analogies are formed thus providing expansion and compression of cement stone. Degree of expansion and self-stressing of cement stone depends not only on composition of sulphated minerals but on ratio and types of clinkers. The higher expansion is reached by the use of high alite containing Portland cement clinker together with sulphoaluminate or sulphoalumoferrite one, the lower expansion is reached by addition of sulphoalumoferrite and sulphoferrite clinkers. These cements are classified as selfstressing, expansive or shrinkage-compensating ones de-pend on the degree of their expansion after 28 days of curring.