Examination of the jarosite-alunite precipitate addition in the raw meal for the production of Portland and sulfoaluminate-based cement clinkers

The aim of the present research work was to investigate the possibility of adding a jarosite-alunite chemical precipitate, a waste product of a new hydrometallurgical process developed to treat economically low grade nickel oxides ores, in the raw meal for the production of Portland cement clinker. The precipitate was also tested in the production of non-expansive, sulfoaluminate-based cement clinker, as a substitute for gypsum because of its high sulfate content. For the Portland clinker, two samples of raw meals prepared, one with ordinary raw materials (reference sample) and another with 1% jarosite-alunite precipitate. Both raw meals were sintered at 1450 °C. For the sulfoaluminate-based clinker, one raw meal contained 20% gypsum (reference sample) whereas the other contained 11% of the precipitate. Both raw meals were sintered at 1300 °C. The results of chemical and mineralogical analyses as well as the microscopic examination showed that the use of the jarosite-alunite precipitate did not affect the mineralogical characteristics of the so produced Portland cement clinker. In the case of sulfoaluminate-based cement clinker, there was confirmed the formation of the sulfoaluminate phase (C4A3S¯), the most typical phase of this cement type.