Cement Energy and Environment

mixes RM-1 to RM-6 were designed by incorporating 0.25, 0.5, 1.0, 1.25, 1.50 and 2.0 wt.% jarosite. A control mix (RM-C) without incorporating jarosite was also prepared for reference study. The fineness of these mixes was maintained in terms of percentage retention on 212 and 90-micron i.e. R212 and R9o. The burnability studies of designed mixes were carried out at the temperatures of 1400 and 1450°C keeping retention time of 20 minutes. The burnt nodules of clinkers were then evaluated for free lime using standard ethanol glycol method, clinker mineral phases by XRD and microstructure by Optical microscopy. The physical characteristics of ordinary Portland cement, prepared using optimizing dose of jarosite in cement raw mix, was studied according to different test procedures described in Indian standard IS: 4031. 3.0 Results and Discussion 3.1 Evaluation of jarosite and other raw materials Chemical analysis of jarosite sample showed 32.25% S03 and 29.69% Fe203 as major oxide constituents with 6.95% CaO, 6.25% Si02, 2.76% ZnO and 4.40% PbO, 0.38% Ti02, 2.36% Na20 and 0.29% K20 (Table 1). The presence of iron, sulphate, alkalies and ZnO in the jarosite showed its compatibility to influence the burning characteristics of cement raw mixes. Analysis of heavy elements such as barium, cadmium, chromium, copper, manganese, strontium , tellurium, lead and zinc were found to be 1700, 290, 110, 1750,450,460,630,40,700 and 22,300 ppm respectively. The lechates in the jarosite sample were determined to be 12 ppm zinc, 6 ppm lead, 0.92 ppm manganese, 0.54 ppm strontium, 0.03 ppm barium, 4 ppm cadmium , 0.04 ppm chromium and 0.07 ppm copper. Table 1: Chemical analysis of jarosite and other raw materials Oxide Jarosite Limestohe Iron ore Bauxite Gypsum a Coa l ash constituents I 1 LOI 33.12 35.28 5.69 : CaO 6.95 45.50 0.77 SiOz 6.25 14.28 20.99 AI203 1.00 1.63 10.54 Fe203 29.69 1.17 59.24 MgO 0.25 1.57 0.13 S03 32.25 nil nil Na20 2.36 0.29 0.09 K20 0.29 0.16 0.35 a: Combined water-14.59%. Si02+1R-20.23% Mineral composition of jarosite showed natrojarosite [NaFe3(S04)2(0H)s] as major mineral constituent with anhydrite [CaS04]. bassenite [CaS04.0.5H20] and sphalerite [ZnS] were detected as other phases. Microscopic study of the sample showed its very fine nature with glass as major component. Glass grains were found to be sticky and rounded to sub-rounded in shape with smooth grain margins. Majority of glass grains detected were in the range of 4 to 16-~m . Particle size distribution showed wide distribution of particles ranging from 296 to 0.972-~m. Size analysis showed its finer nature as -55% fraction passed through 9.25-I.Jm. 18.15 4.59 0.47 26.28 12.26 19.20 38.04 31.61 1.93 17.49 28.19 0.94 10.23 0.47 0.66 3.95 0.05 32.77 9.08 0.03 0.07 1.50 0.06 0.05 1.02 Chemical analysis of limestone sample indicated 35.28% LOI , 45.50% CaO, 14.28% Si02, 1.63% Ai203 and 1.17% Fe203 and 11.55% free silica. Mineralogy of the sample showed predominance of calcite along with quartz, albite, microcline, tremolite and muscovite. Micro– structural analysis of limestone showed its coarse crystalline nature. The average grain size of calcite and quartz was found to be 1578 and 4 76-~m respectively. Chemical analysis of other materials such as iron ore, bauxite, gypsum and coal ash is given in Table 1. The Fe203 content in iron ore was determined to be 59.24% with hematite [Fe203), magnetite [Fe304] and goethite [Fe+ 3Q(OH)] as mineral constituents. Bauxite was used as source of alumina with 31.61% AI203 and 12 -