Use of secondary mineralizing raw materials in cement production. The case study of a stibnite ore

摘要

It has been found that certain foreign elements, despite their low concentration in cement raw mix, may accelerate the sintering reactions and improve the reactivity of the cement raw mix. The subject of this paper is to investigate the possibility to introduce small amounts of minerals, containing these elements, in the cement raw mix. The mineral stibnite was selected in order to introduce Sb and S in the cement raw mix. One reference and four modified mixtures, prepared by mixing the reference sample with 0.5, 1.0, 1.5 and 2.0% w/w of the above 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 ℃. The sintering reactions in all samples were recorded by means of differential thermal analysis (DTA). Scanning electron microscopy (SEM) was used in order to examine the texture of the clinker and study the distribution of the foreign elements in its main phases. Finally, 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 affecting considerably the hydration rate and cement properties.