Effect of High Temperature Reconstruction and Modification on Phase Composition and Structure of Steel Slag

Abstract

This study investigates the pattern of influence of blast furnace slag tempering on the composition and structure of steel slag. The chemical composition, equilibrium phase composition, microscopic morphological characteristics and elemental composition of microscopic regions of steel slag and blast furnace slag modified by high temperature reconstruction were analyzed using X-ray diffractometer (XRD), FactSage7.1 thermodynamic analysis software, mineral phase microscopy and field emission scanning electron microscopy. The results show that blast furnace slag blending can promote the generation of a low melting point phase in the slag, as well as reducing its melting temperature and improving its high temperature kinetic conditions. On the one hand, the incorporation of blast furnace slag was found to promote the generation of C2S in the steel slag and improve its gelling activity. Notably, at 1400 °C, the C2S content (mass fraction) of steel slag modified with 15% high temperature reconstruction reached 39.04%, while that of unmodified steel slag at this temperature was only 16.92%, i.e., only 1/4 of the C2S content in the modified slag. On the other hand, the incorporation of blast furnace slag inhibited the generation of a-C2S-C3P and calcium ferrate minerals, refined the grains of calcium–aluminum yellow feldspar, reduced the alkalinity and promoted the generation of silicate phases with high hydration activity in steel slag.