Mechanical activation of steel slag to prepare supplementary cementitious materials: A comparative research based on the particle size distribution, hydration, toxicity assessment and carbon dioxide emission

The low reactivity of steel slag limits its large-scale application in building materials. Mechanical activation is reported to increase the reactivity of steel slag, but most of the researches only study one of two activation methods (dry- and wet-grinding), and all believe that the reactivity of steel slag is improved. In order to explore the effect of two activation methods on the reactivity of steel slag, both dry-grinding and wet-grinding were used to activate the steel slag in this study. The ground steel slags were characterized by particle size analyzer, X-Ray diffraction (XRD), fourier transform infrared spectroscopy (FTIR) and scanning electron microscope (SEM). The results showed that changing the grinding process mainly affected the particles size distribution and morphology of the steel slag, but had few effects on the mineral composition and crystallinity. The setting time, mechanical properties, hydration products and void structure of ground steel slag-ordinary Portland cement (OPC) blends were investigated. Wet-grinding steel slag-OPC blends are superior to dry-grinding steel slag-OPC blends in all aspects and more suitable for construction sites. Besides, the energy consumption required to activate the steel slag by wetgrinding is about half of dry-grinding. However, activation of steel slag by wet-grinding increases the risk of heavy metals leaching in it, hence, the wet-grinding process needs to be improved.