A development that could redefine the material cycle between steel and cement industry: Swedish steel producer SSAB and Heidelberg Materials have announced a strategic cooperation for the utilization of steel slag in cement production. The partnership aims to use industrial byproducts from steel production as secondary raw materials for clinker production and thereby reduce the clinker factor – a central lever for CO₂ reduction in the cement industry.
Steel slag is created as a byproduct in pig iron production in the blast furnace and in steel refining. It consists of oxidic compounds of calcium, silicon, aluminum and iron – components that also play a central role in Portland cement. So far, steel slag has been predominantly used in road construction or as an aggregate. Direct use as a cement raw material could significantly extend the value chain while simultaneously substituting primary raw materials such as limestone or clay. For Heidelberg Materials, one of the world's largest cement manufacturers, the alliance offers the opportunity to reduce the CO₂ footprint of its binders without relying on expensive carbon capture technologies.
SSAB, in turn, is driving the transformation toward fossil-free steel production and has already received significant funding for the development of green steel, as a recently published report on EU funding shows. The use of steel slag as a cement raw material would enable the company to generate additional revenues from previously underutilized byproducts and strengthen its own sustainability profile. In the circular economy, the cascading use of industrial residues is considered the gold standard: materials are kept in the value chain as long as possible before being landfilled or thermally processed.
However, it remains unclear which cement types should emerge from the slag cycle. The normative classification according to DIN EN 197-1 is decisive: While CEM III already contains high proportions of blast furnace slag, further development toward slag-based binders could require new strength classes and durability properties. Availability and logistics are also critical: steel slag is produced in regionally concentrated areas, while cement plants are distributed throughout Europe. Planners should therefore observe whether the cooperation extends beyond pilot projects and results in scalable production capacities. The alliance could be pioneering for further circular business models between basic material industries – provided that technical, economic and normative hurdles can be overcome.
