Alternative alkali-activator from steel-making waste for one-part alkali-activated slag
Elijah Adesanya, Katja Ohenoja, Andrea Di Maria, Päivö Kinnunen, Mirja Illikainen
Abstract
In this study, the use of desulphurization dust (DeS-dust) generated as a waste material during steel-making process, as an alternative activator to commercial sodium hydroxide in ground granulated blast furnace slag (GGBFS) alkali activation is proposed. The main objective was to decrease the environmental footprint of alkali-activated materials through the reuse of industrial residues. Microsilica was added to increase the amount of soluble silica and enhance the properties of the investigated binders. The results indicate that binders from alternative activator performed better, achieving a 28 days maximum strength of 33 MPa compared to 25 MPa for the sodium hydroxide activated slag. Microsilica addition to the optimum mixes reduces the rate of efflorescence and increases the setting time. Also, microstructural studies using scanning electron microscopy (SEM), x-ray diffraction (XRD) and thermogravimetric analysis (TGA) show both samples having comparable gel formation and structure. Life cycle impact assessment shows significant savings that can be made using alternative activators over sodium hydroxide activated slag. Through the use of this waste material as alternative activator in alkali-activated binders, an environmentally friendly, and cleaner production of alkali-activated binders can be achieved having comparable or superior performance as the reference binder activated with commercial sodium hydroxide.