Unique hot stage modification technique to enhance cementitious properties of electric arc furnace steel slag

Decarburization is a major concern for global industries, particularly the steel and cement sectors, which together contribute nearly 15% of total carbon dioxide (CO₂) emissions. One approach to reducing CO₂ emissions is re-utilizing industrial waste, such as slag, to produce cementitious materials. While ironmaking slag from blast furnaces is conventionally recycled as ground granulated blast furnace slag (GGBS) cement, this technology is not directly applicable to electric arc furnace (EAF) slag, a byproduct of the steelmaking process. This study investigated the potential of direct reduced iron-electric arc furnace (DRI-EAF) steel slag as a supplementary cementitious material (SCM) using a hot-stage modification technique. The experimental sequence follows remelting, modifying, and cooling DRI-EAF slag from a molten state at 1600 °C. Key aspects such as mineralogy, phase transformations, chemical compositions, and cooling conditions were analyzed using experimental data and thermodynamic simulations. The results indicate that adding lime and coke as modifying agents, smelting the slag for 40 min at 1600 °C, and water quenching can produce slag with up to 86% amorphous content. The primary phases precipitated at room temperature were calcium silicates (C2S and C3S). Additionally, the total iron content in the modified slag was reduced to 2 wt%, meeting the requirements for SCM use according to Indian standards. Energy consumption and CO₂ emissions associated with recycling DRI-EAF slag as an SCM were compared with data from conventional cement production. This study highlights the potential of upcycling DRI-EAF slag into SCMs while recovering iron nuggets as secondary resources for steelmaking, contributing to decarburization in both industries.