Optimized determination of PFA (fly ash) fineness with reference to pozzolanic activity

Abstract

The present work evaluates the sieve analysis and specific surface methods for determining PFA fineness, by correlating the fineness results with the pozzolanic reactivity of ash from a single coal source and a single power station. A linear relation was found between the specific surface of PFA and its pozzolanic activity index while the relation between the amount retained on 45μm sieve was linear only in a limited middle range. The air permeability method (subject to an upper maximum carbon content) is seen to be preferable to the sieve analysis method in determining the fineness of fine ash. As more of the ash used nowadays is fine, it is recommended that the specific surface method be re-introduced into ASTM standards.