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Purpose: Many new opportunities are explored to lower the CO2 emissions of the cement industry. Academic and industrial research is currently focused on the possibility of recycling steel production residues in the cement industry, in order to produce new "low-carbon" binders for construction materials. The purpose of this paper is to assess the environmental benefits and costs of steel-residues valorization processes to produce a new binder for construction materials. Methods: Among other stainless steel slag (SSS), argon oxygen decarburization (AOD) slag has the potential to be recovered as a binder during the production of new construction materials. Alkaliactivation and carbonation processes can in fact activate the binding properties of the AOD-slag. However, AOD-slag is today only recycled as low-quality aggregate. For the present study, three different types of construction blocks (called SSS-blocks) were developed starting from the AOD-slag (one block through alkali-activation and two blocks through carbonation). The data from the production of the three construction blocks have been collected and used to perform a Life Cycle Assessment (LCA) study, comparing SSS-blocks production with the production of traditional paver OPC concrete. Results: The analysis showed that SSS-blocks production through alkali activation and carbonation has the potential of lowering some of the environmental impact of OPC-concrete. The LCA results also show that the main bottleneck in the alkali-activation process is the production of the alkali activators required in the process, while the use of electricity and of pure CO2 streams in carbonation lower the environmental performances of the entire process. Conclusions:The valorisation of AOD-slag to produce new construction materials is a promising route to lower the environmental impacts of cement and concrete industries. This product-level analysis stresses the need of updating the LCI datasets for alkali activators and boric oxide, and of widening the scope of the environmental analysis up to system-level, including potential economic interactions and market exchanges between steel and construction sectors.

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