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 SiO 2 gels as well as glassy phases of CaO-SiO 2 and Al 2 O 3 -SiO 2 in the slag surfaces, where, with an increase in the Blaine surface area of the slag, CaO-SiO 2 -type glass becomes dominant and contributes to the evolution of hydration, determined in terms of silicate anion morphology by the trimethylsilylation (TMS) method.
Converter slag contains free lime (CaO) and unstable iron oxides (FeO, FeOOH) that may lead to expansive self‐destruction. A typical industry practice for converter slag has been stabilization by steam curing and autoclaving; however, the stabilization can only reach the surface, and not the inside, of slag particles. A new method is proposed in this study to stabilize the converter slag by heating at a low temperature. After magnetic separation, specimens of converter slag were subjected to heating for 2 h at a temperature of 500°C, resulting in a decrease of free lime content irrespective of the particle size. This effect was attributed to the formation of Ca2Fe9O13 and complicated apatite groups owing to the heating. The iron oxides in the converter slag were analyzed by X‐ray photoelectron spectra. It was found that after heating, the unstable FeO (wustite) content decreased and an oxidized α‐Fe2O3 (hematite) increased. This led to the prevention of the iron‐induced expansion. The rate of heat liberation by the free lime in converter slag was smaller than that of the reagent CaO. This suggests that the presumed free lime is in a different form based on the Ca bond energy in the surface of slag particles.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.