Characteristics of steel slags and their use in cement and concrete—A review

Steel slags are industrial by-products of steel manufacturing, characterized as highly calcareous, siliceous and ferrous. They can be categorized into basic oxygen furnace (BOF) slag, electric arc furnace (EAF) slag, and ladle furnace (LF) slag. They are found to be useful in many fields, such as road construction, asphalt concrete, agricultural fertilizer, and soil improvement. However, better utilization for value-added purposes in cement and concrete products can be achieved. In this paper, an overview of the recent achievements and challenges of using steel slags (BOF, EAF and LF slag) as cement replacement (usually ground into powder form with the size of 400–500 m2/kg) and aggregate in cement concrete is presented. The results suggest that the cementitious ability of all steel slags in concrete is low and requires activation. For the incorporation of steel slags as aggregate in concrete, special attention needs to be paid due to the potential volumetric instability associated with the hydration of free CaO and/or MgO in the slags. Studies have indicated that adequate aging/weathering and treatments can enhance the hydrolyses of free-CaO and -MgO to mitigate the instability. Considering the environmental and economic aspects, steel slags are also considered to have a potential use as the raw meal in cement clinker production.