Characterization of Fly Ash for their Effective Management and Utilization

Abstract

Large amount of fly ash discharged from coal-fired power stations is a major problem. Amount of fly ash available can be recycled, mainly by adding fly ash to cement. However, the addition of fly ash to cement is limited because the production rate of cement is leveled off, and also the concentration of fly ash in cement is limited.

Researchers have studied the aspect of particle size distribution, permeability, slurry flow characteristics, settling characteristics, slump characteristics and so on for mill tailings. Fly ash in terms of particle size and mineralogical composition is similar to mill tailings. There is however not much literature available on direct placement of fly ash as a fill material. Investigations on the fly ash have been largely confined to determining physico-chemical properties, strength properties (as cement substitute or with binders). The present study therefore makes use of literature available in terms of fly ash, to design and conduct different experiments on settling rate and hydraulic transportation aspects of fly ash.

Different experiments were conducted to find the pH at different levels of lime, cement and gypsum. These were done to further utilize the cementing property of fly ash and its use for support and fill the mine voids as well as construction of cement of different strength levels. It was observed that the strength level increase with the increase in the percentage of lime and it was observed to be maximum at 4% of lime and 8 % cement and 4% gypsum. Thus as pH is directly related to strength so it indicated that the strength characteristics was further enhanced using the aforesaid composition. The SEM of the samples were done to study the characteristics of individual elements as the element having spherical shapes showed maximum pozzolanic character.