Geopolymers, fly ash reactivity and mechanical activation

The foucs this paper is on the reactivity of fly ash in relation to its geopolymerisation, that is structure and properies of geopolymer. A comparision of the mechanically induced reactivity by vibration and attrition milling and glass content induced reactivity obtained through size classification in a high speed air classifier has been made. It has been shown that for the fly ash of nearly same size (~ 5 µm), mechanical activation results in higher reactivity or geopoymerisation rate as compared to the air classified samples. Reactvity can also be altered by mixing raw fly ash with processed fly ash. Much wider variation in the reactivity is possible by mixing raw fly ash with mechanically activated fly ash than with classified fly ash. Higher reactivity of the mechanically activated fly ash results higher strength vis-à-vis raw and air classified fly ash