In Retrospect: Some Peculiarities Observed in the Mechanical Activation of Ground-Granulated Blast Furnace Slag and Fly Ash

The focus of this paper is on the mechanical activation of aluminosilicate wastes, namely ground-granulated blast furnace slag (GGBFS) and fly ash (FA). The subject is of relevance to the development of improved blended cement and geopolymers. The presence of large quantities of amorphous phases in these materials makes them unique and challenging from the point of view of characterization. Interesting findings, some of which were first-time discoveries, are reviewed with emphasis on the role of the milling device (mill type, milling energy, and environment), characterization challenges, and the manifestation of mechanically induced reactivity. The relative importance of mechanical activation vis-a-vis reaction temperature is highlighted based on calorimetric maps for the geopolymerisation of fly ash.