Cement Energy and Environment

5% gypsum which is made up of mixtures of mineral gypsum and jarosite. The mineral gypsum was decreasing from 4 to 0% and the jarosite simultaneously increasing from 0 to 4'Yo in the same proportion. These OPC samples were prepared by inter-grinding of all components simultaneously in laboratory ball mill and were studied for various physical characteristics such as Blaine's fineness, consistency, setting time, compressive strength at 1, 3, 7 and 28 days, soundness and heat of hydration at 7 and 28 days using different Indian standard test procedures described in Indian Standard IS: 4031 . The particle size distribution (PSD) of material was studied using Microtrac S3500 particle size analyser. The cement sample containing optimized dose of jarosite in place of mineral gypsum was hydrated for different time intervals of 1, 3, 7, 28, 90 and 180-days by maintaining water to cement ratio of 0.4 and studied for hydrated products development by XRD. The resistance to different aggressive environmental conditions was studied by measuring the compressive strength of hardened cement mortar cubes by immersing in sulphate (0.33N NazS04, pH-5.99) and chloride (0 .5N NaCI, pH-6.43) solutions up to the period of 6 months and compare with the strength development of mortar cubes cured in distilled water. 3.0 Results and Discussions 3.1 Characterization of Jarosite and Other Materials Chemical analysis of jarosite sample indicated 32.25% S03, 6.95% CaO and 4.32% insoluble residue along with Mineralogy of jarosite showed natrojarosite [NaFe3(S04)z(OH)s] as major mineral constituent with anhydrite [CaS04] and bassenite [CaS04. 0.5HzO] in moderate to small amount (Fig 1). Microscopic study 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-l..lm. Needle to lath shaped gypsum grains with corroded margins were observed randomly scattered along with few rod shaped gypsum grains with corroded margins. Particle size distribution of jarosite showed wide distribution of particles varying from 296 to 0.972-l..lm and its finer nature as - 55% fraction passed through 9.25-I.Jm. Table 1: Chemical analysis of jarosite and other materials used Oxide Jarositea Clinker Mineral Constituents gypsum LOI 33.12 1.11 16.90b CaO 6.95 63.25 30.03 Si02 6.25 21 .61 8.oc Al203 1.00 5.39 0.26 Fe203 29.69 5.08 0.16 MgO 0.25 1.07 0.09 S03 32.25 0.75 43.81 Na20 2.26 0.20 0.07 1<20 0.29 0.50 0.01 a: Zn0-2. 76%, Pb0 -4. 40% and 0.38% Ti02 b: Combined water, b: Si02+/R considerable amount of alkalis Na20 and KzO (Table 1). Heavy elements such as barium , _.------------------------------------------------. cadmium, chromium, copper, manganese, strontium, tellurium, lead and zinc were determined to be 1700, 290, 110, 1750, 450, 460, 630, 40,700 and 22,300 ppm respectively and results of leachbility of the sample showed presence of negligible amount of leachates. 000 Fig 1: X-ray diffractogram of jarosite 20 - .