Integrated and innovative steel slag utilization for iron reclamation, green material production and CO2 fixation via accelerated carbonation

Huge amounts of iron and steel slags are generated annually worldwide from integrated manufacturing processes and/or the electric arc furnace. However, conventional uses of untreated iron and steel slags in civil engineering have encountered several technological barriers, such as fatal volume expansion, heavy metal leaching and low cementitious property of slag. In this study, the physico-chemical properties of four different types of slag, blast furnace slag, basic oxygen furnace slag, electric arc furnace slag and ladle refining furnace slag, are illustrated. The challenges and barriers in direct use of steel slags in civil engineering are comprehensively summarized. To overcome the barriers of slag utilization, an accelerated carbonation process is proposed and reviewed in terms of theoretical perspectives and practical considerations. Since diluted CO₂ in flue gas can be directly introduced for carbonation, additional environmental and economic benefits such as CO₂ emission reduction are obtained. In addition, the performance of various new carbonated slags or products is systematically reviewed, in terms of changes in the physico-chemical properties of carbonated slag. To facilitate the industrialization of accelerated carbonation, several suggestions are made regarding future research directions.