The partnership between Swedish steel company SSAB and Heidelberg Materials marks a shift in perspective in the decarbonization strategy of energy-intensive industries. Rather than isolated reduction pathways, both companies are focusing on cross-industry material circular economy: steel production residues become a resource for cement production. The cooperation model could become pioneering for further industrial symbiosis between steel, concrete, and other basic materials industries.
Steel slag instead of primary raw materials: The technical principle
Steel production generates significant quantities of slag – a mineral byproduct that results from the smelting of iron ore and the recycling of steel scrap. This slag contains calcium, silicon, and aluminum compounds that are also found in conventional cement raw materials. SSAB produces hundreds of thousands of tons of these residual materials annually at its Scandinavian and European facilities.
Heidelberg Materials now intends to use these slags as a substitute for natural raw materials in the production of cement binders. The approach is not entirely new – blast furnace slag has been used as a component of Portland cement or as an independent binder for decades. However, the special feature of the SSAB cooperation lies in the targeted integration of electric arc furnace slag and steel mill waste from modern production processes that increasingly operate fossil-free.
SSAB is pursuing the HYBRIT project to switch to hydrogen-based steel production, which generates completely different slag compositions than conventional blast furnace processes. The partnership with Heidelberg Materials enables it to systematically utilize these new waste streams as well.
CO2 balance: Double leverage through material substitution
The cement industry is among the world's largest industrial CO2 emitters. Approximately 60 percent of emissions result from the calcination of limestone to clinker – a chemical process that unavoidably releases CO2. A further 40 percent results from the energy required for firing processes at temperatures above 1,400 degrees Celsius.
The use of steel slag as a raw material acts on both levels: First, it reduces the proportion of primary limestone and thus process-related CO2 emissions. Second, slag-based binders typically require lower firing temperatures or can sometimes be granulated and ground without cooling, which reduces energy consumption. Heidelberg Materials has previously achieved clinker substitution rates of up to 30 percent through alternative raw materials – while simultaneously meeting norm requirements for concrete strength and durability.
SSAB gains an additional advantage: Instead of bearing landfill costs for slag or disposing of it with limited added value as road construction material, a higher-value sales channel emerges with potentially better margin structures. Industrial symbiosis transforms a cost factor into a revenue source.
Cross-industry cooperation as an accelerator of decarbonization
The SSAB-Heidelberg partnership illustrates a fundamental principle of increasingly relevant decarbonization strategies: individual industries can achieve their emission targets faster and more cost-effectively when they orchestrate material flows, infrastructure, and technologies across industries. Such industrial symbiosis is already established in the chemical and refinery industries, but remains underdeveloped in the building materials industry.
Several factors currently favor such cooperations: Stricter EU regulation through emissions trading (ETS) and the Carbon Border Adjustment Mechanism (CBAM) increase economic pressure on CO2-intensive industries. At the same time, requirements for product life cycle assessments are rising due to national building codes and private certification systems such as DGNB or LEED. Concrete manufacturers and construction companies increasingly demand cements with reduced CO2 footprints to achieve their own sustainability goals.
The cooperation also demonstrates how different time horizons of industrial transformation can be synchronized. While SSAB is preparing a radical technological leap with fossil-free steel production, Heidelberg Materials is relying on incremental optimization of existing processes through raw material substitution, alternative fuels, and cement formulations with lower clinker content. Both pathways complement each other: the steel slag from the HYBRIT process becomes a resource for the next generation of green cements.
Regulatory frameworks and standards
The commercial scaling of slag-based cements faces regulatory challenges. Cement formulations must meet the strict requirements of the EN 197 standard series, which defines minimum clinker content, strength classes, and durability. Blast furnace slag is already approved as a main constituent, but new slag types from electric arc furnace-based or hydrogen-reduced steel processes require additional performance evidence and possibly standard adjustments.
Heidelberg Materials has extensive laboratories and testing capacities to validate the technical properties of new binder combinations. The partnership with SSAB is likely also aimed at generating data early for approval procedures and jointly approaching standards bodies. In parallel, environmental product declarations (EPDs) must be created that transparently document the reduced CO2 footprint and make it communicable in competition.
Market potential and scaling challenges
Global cement production stands at around four billion tons annually, steel production at approximately two billion tons. Even if only a fraction of steel slag is suitable for cement applications, this represents significant substitution potential. Heidelberg Materials produces over 100 million tons of cement globally per year, making it one of the largest suppliers. Accordingly, the possible uptake lever for SSAB slag is large.
However, geographic and logistic factors are critical: steel mills and cement plants are not always located in close proximity. Transport costs for bulk commodities like slag can quickly offset CO2 and cost advantages. The cooperation will therefore likely initially focus on European sites where both companies are present – for example, in Scandinavia, Germany, or the Benelux countries.
Another scaling obstacle is the heterogeneity of steel slags. Depending on the steel grade, scrap quality, and process management, chemical composition and mineralogical phases vary significantly. Heidelberg Materials must therefore develop quality assurance systems that ensure consistent binder performance despite fluctuating input materials. This requires close coordination between steel mill and cement mill and possibly preprocessing steps such as fractionation or separation of magnetic components.
Perspective: Industrial symbiosis as an infrastructure project
In the long term, the SSAB-Heidelberg cooperation could become the nucleus of a larger industrial ecosystem. Industrial parks are conceivable where steel mills, cement works, ready-mix concrete manufacturers, and possibly also recycling facilities for construction waste are spatially and procedurally integrated. Such clusters enable short transport routes, shared infrastructure use (for example, for heat or logistics), and more efficient material flow management.
The EU promotes such concepts under its Circular Economy Action Plans and the Industrial Emissions Directive. National funding programs for climate-neutral industrial processes could also provide incentives for joint investments. The partnership between SSAB and Heidelberg Materials is likely to be a signal to policy makers to improve regulatory and financial frameworks for cross-industry decarbonization projects.
In parallel, SSAB is working on further projects to utilize its fossil-free steel production, supported by EU funding of 20 million euros. These initiatives demonstrate that the transformation of the steel industry is not occurring in isolation, but is systematically integrated with downstream value chains.
Outlook: From pilot phase to standard practice
The announced cooperation is still in an early phase. Neither SSAB nor Heidelberg Materials has published details on volume targets, locations, or timelines. Typically, such projects first undergo laboratory tests, followed by pilot plants at ton scales, before commercial scaling occurs. This process can take several years.
Critical to success will be whether slag-based binders not only work technically but can also compete economically with conventional Portland cements – or whether CO2 prices and regulatory incentives shift the cost structure in favor of the green alternative. Heidelberg Materials has repeatedly emphasized in the past that decarbonization can only succeed if it makes economic sense or is supported by political frameworks.
For the building materials industry as a whole, the SSAB-Heidelberg partnership could be a turning point: away from linear value chains toward circular networks where waste from one industry becomes raw material for another. Similar approaches are already being pursued by other players – for example, the use of fly ash from coal-fired power plants or the integration of recycling materials into new concrete mixes. The challenge is to develop such individual initiatives into systematic, scalable business models.
The cooperation exemplifies how industrial decarbonization can work: through technical innovation, cross-industry collaboration, and intelligent use of existing material flows. Whether the model proves viable will become clear in the coming years – and could possibly set standards for further partnerships between the steel, cement, and construction industries.
