Recycling of Malaysia's EAF steel slag waste as novel fluxing agent in green ceramic tile production: Sintering mechanism and leaching assessment

Abstract

Electric arc furnace (EAF) slag is one of the most common by-products in the steelmaking industry. Despite various efforts of using this waste, there is yet a clear indication of EAF slag being recycled into commercial ceramic products, and most EAF slag ended up being disposed of through landfilling. Thus, a more thorough assessment is necessary to assure and convince the public regarding the potential benefits of incorporating EAF slag into the production of commercial ceramic products. In this research work, EAF slag was used as raw materials in the production of ceramic tiles. The EAF slag was crushed and ground into micron size powder before wet-mixed and milled with ball clay according to specific body formulations. This mixture was dried, compacted and fired at 1100–1180 °C. The results showed that body formulation of 50 wt% EAF slag–50 wt% ball clay and fired at 1180 °C yield ceramic tiles with most favorable properties with lowest water absorption (0.16%), lowest apparent porosity (0.48%), highest bulk density (2.95 g/cm3), and highest modulus of rupture (92.4 MPa). A sintering mechanism analysis was conducted, and it was found that the EAF slag functions as a fluxing agent to form a glassy phase, while contributed to the formation of anorthite and wollastonite during firing. The presence of these phases enhanced the densification of ceramic tiles. A leaching assessment was conducted on the ceramic tile samples, and the researchers found that heavy metal concentrations in the leachate are within the safety limit regulated by the Department of Environment Malaysia when the tiles are fired at 1180 °C. Through benchmarking with commercially available ceramic tiles and MS ISO13006:2014 Standard, the EAF added ceramic tiles have great potential to be used as heavy-duty floor tiles.