Transformation of secondary steelmaking slags towards a hydraulic binder via controlled cooling and post-processing

摘要

This work explores the possibility of transforming secondary steelmaking slags to a cementitious binder by: a) high cooling-rate solidification and b) mechanical activation via high energy milling in a bead mill. Industrially produced and synthetic slags with various basicities were used in the experiments. Hydraulic activity was evaluated by means of isothermal calorimetry, scanning electron microscopy (SEM), thermogravimetry (TGA) and quantitative X-ray diffraction analysis (QXRD). For the study of the cooling path, a melt spinning granulation device was employed in addition to water quenching experiments. Results demonstrate that the beta to gamma-2CaO.SiO2 transformation can be suppressed and that the end product is hydraulically active upon mixing with water. For the mechanically activated samples, 2h and 6h milling resulted in partial amorphisation and significant increase of hydraulic activity compared to the as-received slags. The work concludes with a proposed hydration behavior for the major slag phases.