USE OF SECONDARY MINERALISING RAW MATERIALS IN CEMENT PRODUCTION. THE CASE STUDY OF A STIBNITE ORE

Certain foreign elements in low concentration may accelerate the sintering reactions and improve the reactivity of cement raw mixes. The possibility of introducing small amounts of minerals containing these elements in cement mixtures was studied. The mineral stibnite was selected in order to introduce Sb and S in the mix. One reference and four modified mixtures, prepared by mixing the reference sample with 0.5, 1.0, 1.5 and 2.0 wt% of the mineral, were studied. The effect on the reactivity of the raw mix was evaluated on the basis of the unreacted lime content in samples sintered at 1000, 1100, 1200, 1300, 1350, 1400 and 1450 C. The sintering reactions in all samples were recorded using DTA. SEM was used in order to examine the texture of the clinker and study the distribution of the foreign elements in its main phases. The hydration rate in the cement pastes and some cement properties were measured. It was concluded that the added mineral improves the burnability of the cement raw mixture without adversely affecting the hydration rate and cement properties. 14 refs.