Alkali activated slag cement doped with Zn-rich electric arc furnace dust

Abstract

Steel production in electric arc furnaces yielding formation of two waste materials, toxic electric arc furnace dust (EAFD) and non-hazardous electric arc furnace slag (EAFS). EAFD presents a potential hazard to the environment as it is characterized by the presence of heavy metals. This study dealt with the synthesis and characterization of alkali activated slag cement (AAS) based on EAFS with addition of 1-7% of Zn-rich EAFD dopant. Effects of slag replacement with dust on the compressive strength, physico-chemical, mineralogical and morphological properties of AAS cement were evaluated. This replacement lead to the development of porosity of AAS matrix, and retardation of slag alkali activation which resulted in the weakening of the AAS structure and hence in compressive strength decrease as pure AAS cement compressive strength was 21.04 MPa while AAS doped with 7% of EAFD reached only 8.4 MPa. On the other hand, AAS doped with 5% of EAFD exhibited compressive strength of 13.82 MPa, making it is still suitable for construction purposes... Scanning electron microscopy coupled with energy dispersive X-ray spectroscopy (SEM/EDS), scanning transmission electron microscope (STEM) in high angle annular dark field (HAADF) mode, X-ray powder diffraction (XRPD) investigations and standard EN 12457-2 leaching test provided information on the ability of AAS based on EAFS to fix Zn in AAS matrix.. The concentration of Zn in leachate of AAS cement doped with 5% of EAFD was 9.20 mg/kg which is below the limit prescribed for the granular waste acceptable at non-hazardous landfills according the European Directive 2003/33/CE.

Keywords

• EAF steel making slag
• EAF steel making dust
• Zn
• Alkali activation