Corrosion of granulated glassy blast furnace slags in aqueous solutions

Structure and reactivity of several commercial and laboratory granulated gl assy blast furnace slags were investigated. From the compositions NBO/T was calculated, the number of nonbridging oxygens per tetrahedron. Electron sp in resonance spectrometry answered questions regarding the coordination num bers of the ions Mn2+ (Mg2+) and Ti+. Both the hydrolytic reactivity of the slag glasses in water and their corrosion mechanisms in 0.1 mol/l KOH mode l pore solution were studied. Scanning electron and atomic force microscopy showed the development of gel-like phases an the slag grains. Although dis tinct features could be resolved already only the nanoscale in-depth profil es obtained by secondary neutral mass spectrometry helped to enlighten the complex reaction sequences. Thus, for example, it could be shown that first Mg2+-rich gel phases developed by the corrosion process, however, after so me hours the leach solutions became supersaturated successively with the co nsequence of forming a secondary calcium-silicate hydrate phase by a redepo sition process. This phase showed a tobermorite-like structure. Al2O3- and TiO2-rich blast furnace slags were more stable than the CaO-rich materials and they also displayed reaction mechanisms at least partly dissimilar to t he just mentioned.