Mineralising effect of jarosite: a zinc industry by-product in the manufacturing of cement

The presence of mineral phases bearing iron, sulfur, sodium, potassium and zinc in jarosite, a residual by-product of the zinc industry, showed its suitability for use as a mineraliser in the development of clinker mineral phases. Different cement raw mixes RM-1 to RM-5, prepared by incorporating 0·5–1·75 wt% jarosite, maintaining clinker parameters LSF: 0·92, SM: 2·14–2·22, AM: 1·09–1·13, potential phases C₃S: 57·73–58·84, C₂S: 17·37–17·97, C₃A: 5·57–6·00 and C₄AF: 14·06–14·42 and fired at temperatures of 1300, 1350, 1400 and 1450°C showed the mineralising effect of jarosite in terms of rapid lime assimilation and improved clinker mineral phase formation as compared to a control mix prepared without using jarosite. The optimum clinkerisation temperature was reduced by ∼50°C. The physical characteristics of the cement sample (OPC-4) prepared with 1·5 wt% optimised dose of jarosite showed a 18–25% increase in compressive strength development at early ages as compared to the control cement. As jarosite contains heavy elements such as barium, cobalt, copper, lead, manganese, strontium, zinc and so on, a leaching study was taken up by immersing 28-d hardened neat cement cubes in aggressive mediums such as sulfate, chloride and alkaline solutions along with lean water over a period of 24 months. The leachates contents were found to be in negligible amounts, indicating fixation of heavy elements in clinker mineral phases.