A COMPOSITION FOR MAKING CEMENTITIOUS BINDERS BASED ON HIGH FLY ASH CONTENT, CLAY POZZOLANA AND OTHER MINERAL OR INDUSTRIAL WASTES FOR USE IN CEMENT MORTARS AND CONCRETE

摘要

Over 150 million tonnes of industrial wastes are produced from various agro-industrial processes per annum in India. The major solid industrial wastes have been identified are fly ash, phosphogypsum, fluorogypsum, lime sludge, red mud, mine tailings etc. These materials require immediate attention to reduce environmental pollution and health hazards and at the same time to mitigate disposal problems associated with them. Investigations were, therefore, undertaken to formulate cementitious binders by judicious blending of the ground fly ash with the gypsum anhydrite (Fluorogypsum or by-product gypsum), hydrated lime sludge, calcined clay, portland cement including a chemical activator. It was found that cementitious binder of high compressive strength may be produced by admixing 10-15 wt.% gypsum anhydrite (fluorogypsum), 5-20 wt.% calcined clay pozzolana, 15-20 wt.% lime sludge, 10-15 wt.% portland cement and 1-2 wt.% chemical activator (Na2SO4.1OH2O) with 50-60 wt. % of fly ash. The cementitious binders were produced with and without addition of portland cement. The strength development of binders take place through formation of ettringite (C3A. 3CaSO4. 32H2O), C-S-H and C4AH,3. The binders are emminently suitable for making cement mortar of high compressive strength and high workability properties. Cost - wise, these binders are cheaper than the portland cement and conform to the strength characteristics of BS : 6610-1991, Specification for pulverized fuel ash pozzolanic cement.The findings further infer that fly ash can be used in the range 50-60% in formulating these binders along with other wastes to alleviate environmental pollution.