Generation, utilization, and environmental impact of ladle furnace slag: A minor review

More than 20 million tons of ladle furnace slag are produced annually. This slag is mainly treated by stockpiling; however, stacking results in dust and heavy metal pollution. Utilizing this slag as a resource can reduce primary resource consumption and eliminate pollution. In this review, existing studies and practices related to slag are discussed, and applications for different slag types are analyzed. The findings reveal that under alkali- or gypsum-activated conditions, CaO-SiO2-MgO, CaO-Al2O3-MgO, and CaO-SiO2-Al2O3-MgO slags may act as a low-strength binder, a garnet- or ettringite-based binder, and a high-strength cementitious material, respectively. Partial replacement of cement with CaO-Al2O3-MgO or CaO-SiO2-Al2O3-MgO slag can adjust the settling time. Meanwhile, CaO-SiO2-Al2O3-FeO-MgO slag combined with fly ash can be used to prepare a high-strength geopolymer, and CaO-Al2O3-MgO and CaO-SiO2-MgO slags may yield high carbon dioxide sequestration percentages. However, the aforementioned applications could lead to secondary pollution because these slags contain heavy metals and sulfur. Removing them or suppressing their dissolution is therefore of significant interest. Reusing hot slag in a ladle furnace could be an efficient utilization strategy because it can recover heat energy while utilizing the components of the hot slag. However, adopting this approach necessitates the further development of an efficient method for removing sulfur from hot slag. Overall, this review elucidates the relationship between the utilization method and slag type and identifies future research directions, thereby providing references and guidance for future research on slag utilization.