Indian Fly Ashes: Their Characteristics and Potential for Mechanochemical Activation for Enhanced Usability

In India, the generation of electricity is overwhelmingly dependent on the combustion of high-ash coal. The present availability of fly ash has already exceeded 130 million tons, and its generation is likely to reach 170 million tons by 2011–2012. Although the present gainful use of fly ash is close to 50% of the quantity generated, a countrywide directive has been established to effectively use the entire quantity generated in 2011–2012. This objective can be met only if one looks for newer avenues of bulk use that have not been tried successfully. To achieve this target, several technological endeavours are in progress in India to enhance the quality and reactivity of fly ashes through mechanochemical activation. The regular and experimental technologies of comminution and size classification have not resulted in producing submicrocrystalline or nanocrystalline particles from the crystalline fly ashes; and hence, no quantum jumps in their reactivity have been realized. Therefore, the need for converting the fly ash grains to submicrocrystalline particles is critical if the performance of fly ashes has to approach that of silica fume or silica gel.