Granularity and surface structure of ground granulated blast-furnace slags

Ground granulated blast-furnace slags (GGBS) show improved hydration reactivity when granularity fineness increases, but the reason for the improvement in reactivity is still unknown. GGBS specimens with Blaine surface areas of 4680, 6470, and 8050 are analyzed, but the conventional reactivity criteria, such as degree of vitrification, basicity, and mineralogical composition, of the GGBS show no significant differences. X-ray photoelectron spectroscopic analysis, however, successfully distinguishes and identifies SiO2 gels as well as glassy phases of CaO-SiO2 and Al2O3-SiO2 in the slag surfaces, where, with an increase in the Blaine surface area of the slag, CaO-SiO2-type glass becomes dominant and contributes to the evolution of hydration, determined in terms of silicate anion morphology by the trimethylsilylation (TMS) method.