Cement Energy and Environment

... Chemical analysis of OPC clinker showed presence of usual oxide constituents with 0.75% 803, and 2.65% IR. The free lime content was found to be 0.48% indicating well burnt clinker with 58% alite, 17% belite, 4% C3A and 16% C4AF as determined by XRD. Chemical analysis of mineral gypsum indicated 43.81% 803, 30.03% CaO, 8.00% 8i02+IR and 16.90% combined water estimated at 220°C. The chemical composition of mineral gypsum indicates higher CaO and 803 contents as compared to jarosite. The purity of gypsum based on 803 percentage was found to be 93.75%. Mineral composition of the above sample showed gypsum [Ca(804)(H20 )2] as major mineral phase with small amount of a.-quartz [Si02]. 10 20 30 60 120 Time (minutes, I" Mineral gypsum a Jarosite I (a) 3.2 Solubility of Jarosite vis-a-vis Mineral Gypsum The rate of availability of sulphate ions from jarosite was found to be higher as compared to mineral gypsum in both distilled (pH=?} and alkaline water (pH=10) (Fig's Fig 2a & b) and could be attributed to the presence of alkali bearing mineral phases in jarosite sample. The percentage of soluble sulphate ions from jarosite at initial stage of reaction of 10, 20, 30, 60 and 120 minutes in distilled water were found to be 72.76, 69.70, 59.13, 70 .0 and 84.83% respectively as compared to 37.21, 56.16, 31 .28, 33.79 and 34.93% corresponding to mineral gypsum indicating much higher rate of dissolution of sulphate bearing phases in jarosite. The rate of availability of sulphate ions from jarosite was found to be slightly more in case of dissolution in alkaline water. 10 20 30 60 120 Time (mlnuteal IIi! Mineral gypsum DJa.rosite I (b) Fig 2: Solubility of S03ions in (a) distilled and (b) alkaline water 3.3 Performance Evaluation of OPC Samples Containing Jarosite as Set Controller Different ordinary Portland cement samples (OPC-1 to OPC-5) were prepared by incorporating different doses of jarosite replacing mineral gypsum. Control cement OPC-C was also prepared using 100% mineral gypsum for comparative study (Table 2). The 803 contents in cement samples OPC-1 to OPC-5 were determined to be in the range of 2.46 to 2.23% whereas in control cement OPC-C, the S03 content was 2.75%. All the cement samples prepared were found to conform to the chemical requirements of 803 in cement as specified in Indian standard 18:269-2015 specified for OPC-43 grade cement. Table 2: Composition of OPC samples prepared Sample Weight percentage Chemical parameters (%) code Clinker Gypsum Jarosite S0 3 LOI MgO Cl IR (CL) (MG) (JS) OPC-C 95.0 5.0 2.75 3.05 0.91 0.013 0.83 OPG-1 95.0 4.0 1.0 2.46 2.64 0.59 0.014 0.60 OPC-2 95.0 3.0 2.0 2.38 2.50 0.60 0.014 0.89 OPC-3 95.0 2.0 3.0 2.28 3.02 0.64 0.013 0.62 OPC-4 95.0 1.0 4.0 2.36 2.31 1.06 0.013 0.64 OPC-5 95.0 0.0 5.0 2.23 3.05 0.64 0.012 0.64 OPC-43 grade (18:269-2015) S: 3.5 s:5.0 S:6.0 s: 0.1 S:5.0 21