Comparative life cycle assessment to maximize CO2 sequestration of steel slag products

[Display omitted] •Steel slag block can achieve a negative CO2 emission under certain conditions.•Carbonation curing process contributes a large proportion of total GWP.•Carbonation duration should be shortened to improve carbonation efficiency.•Flue gas carbonation method can help produce carbon negative products. Carbon capture utilization and storage is one of the most eminent technologies to mitigate climate change. Steel slag can be treated as a potential material owing to the large percentage of alkaline silicate minerals contained. Herein, a comparative evaluation of environmental impacts of producing artificial cold-bonded steel slag aggregates and pure steel slag blocks was carried out using life cycle assessment method. The global warming potential results show that steel slag block is possible to achieve a negative emission. Detailed results indicate the carbonation curing and production of carbon dioxide constitute a large proportion of emissions. The production of carbon dioxide account for 12% and 50% of total CO2-eq emissions for artificial steel slag aggregate and steel slag block respectively, thus, cut-off rule cannot be applied. The sensitivity analysis of transport shows that global warming potential will become positive under long transport distance. Meanwhile, the diesel consumption for transportation also has a significant impact on the acidification potential and eutrophication potential. This study also investigated the working efficiency of different grinding machine and horizonal roller mill was determined to be the most efficient and energy saving technique, considering its output particle size of steel slag powder and equipment wear during operation.