INFLUENCE OF SULFUR ON THE COMPOSITION OF BELITE-RICH CEMENT CLINKERS AND THE TECHNOLOGICAL PROPERTIES OF THE RESULTING CEMENTS

Upon the absence of alkalies, increasing sulfate contents in belite-rich cement cliners induced a significantly higher belite content which is associated with a decrease in the alite content and, consequently, a reduction in the compressive strengths after 2 days of the resulting cements. The compressive strengths of the cements after 28 and 90 days are markedly raised by the addition of sulfate and this effect is enhanced by rapid clinker cooling. In the Belite-rich cement clinker the major portion of SO//3 is incorporated in the belite as main clinder phase and occurs in the form of sulfate phases, mainly CaSO//4. Stabilization of the high-temperature forms alpha and alpha prime of belite cannot be achieved by SO//3 contents up to 1. 5%) in belite-rich cement cliner, corresponding to 0. 6 to 0. 8% SO//3 in the belite phase. On the contrary, a lattice-disturbed sulfate-bearing beta -phase of improved hydraulic activity results. The addition of alkali oxides up to a maximum of 1. 0% with a sulfatizing degree between 80 and 100, has positive effects on the strength development of the resulting cements.