The foucs this paper is on the mechanically induced reactivity of granulated blast furnace slag and fly ash. Mechanical activation of blast furnace and fly ash is mill specific, that is, it depends on milling mechanism and mill dynamics. Slag after wet milling in an attrition mill hydrates completely in sharp contrast with ball milled slag of same fineness (~ 12 µm). The hydration product of attrition milled slag shows a number of unique characteristics, for example : increased crystallinity of the phases in the hydration product with an increase in the milling time, formation of cement phases that forms under hydrothermal conditions, etc. The vibratory milled fly ash showed higher lime reactivity vis-à-vis raw and attrition milled fly ash. The origin of mechanically induced reactivity, development of improved blended cements and their prospects are presented
