Utilization Potential of Steel Slag for CO2 Sequestration and as a Filler Aggregate in Mortars

Abstract Steel slag is an abundant by-product of steelmaking and a promising candidate for CO 2 sequestration due to its favorable chemical composition and mineralogy. In this study, the CO 2 sequestration capacity of the processed steel slag Ekominit was analyzed. Ekominit is a mineral product obtained by processing a mixture of electric arc furnace (EAF) stainless steel slag and ladle slag, currently used only for simple engineering constructions. The study demonstrated a promising sequestration capacity of 127.4 g CO 2 per kg of Ekominit, measured using direct semi-dry carbonation under ambient pressure at 40 ± 0.5 °C, 80 ± 3.2% relative humidity, and 20 ± 0.1 vol% CO 2 for 5 days, which is within the typical range reported for carbonated steel slags (100–150 g CO2 / kg slag ). Although Ekominit did not show sufficient potential as a supplementary cementitious material in mortar, the results confirmed that its incorporation as a filler—with or without carbonation treatment—enhances both the flowability and compressive strength of the mortar. This research emphasizes the dual-function potential of Ekominit: it captures CO 2 , contributing to the decarbonization of the steel sector, and enables its reuse in construction materials, even improving the performance of mortars when using such carbonated Ekominit as fillers. Through such industrial symbiosis, environmental impact is further reduced by substituting virgin raw materials with secondary products. Graphical Abstract