Rejuvenation of granulated blast furnace slag (GBS) glass by ball milling

Abstract Differential scanning calorimetry, thermogravimetry and gas analysis were used to study the impact of high-energy mechanical milling (HEMM) on the rejuvenation of a granulated blast furnace slag (GBS). It is found that milled GBS – ground granulated blast furnace slag (GGBS) in practice – shows an enormous release of exothermic heat in the sub-Tg range upon heating at 10 K min−1, which increases with milling time and exceeds more than three times that of the unmilled GBS. Heating of GGBS revealed that the energy release of HEMM-activated glasses occurs at considerably lower temperatures than observed for thermally excited glasses (hyperquenched fibers). The difference in the characteristic release temperatures is assigned to two different relaxation mechanisms. The former (HEMM), is due to relaxation of structural defects on the surface of the powder particles, whereas the latter (hyperquenched glass), comprises relaxation of the entire glass structure throughout the volume.