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General comment This specific EPD covers Linz-Donawitz process slag (BOFS), a by-product generated during the conversion of pig iron into crude steel. As a metallurgically inherent material, BOFS is an unavoidable part of the steelmaking process.
Due to its defined chemical composition—primarily consisting of iron oxide, calcium oxide, and silicon dioxide—BOFS is particularly well-suited as a high-quality secondary raw material for road construction.
When used as aggregate in various construction applications, BOFS is processed under quality-controlled conditions in accordance with the requirements of the relevant harmonized European standards:
EN 13043 – Aggregates for bituminous mixtures and surface treatments for roads, airfields, and other trafficked areas
EN 13242 – Aggregates for unbound and hydraulically bound materials for use in civil engineering work and road construction
EN 13383 - Armourstones
The specific use of the product is subject to the respective national legal regulations at the place of use, particularly with regard to environmental compatibility, installation classes, and approval procedures.
BOFS consists predominantly of oxidic components, particularly iron oxide (Fe₂O₃), calcium oxide (CaO), and silicon dioxide (SiO₂). These are complemented by smaller proportions of aluminium oxide (Al₂O₃), magnesium oxide (MgO), and other trace elements.
The composition results from the metallurgical process in the LD converter and is characterized by a crystalline structure with high mechanical strength.
BOFS can be recycled and reused for the same purpose after excavation, crushing and screening.
According to the German Substitute Building Materials Ordinance (EBV), BOFS is classified as SWS 1.
pH value: 9–13
Electrical conductivity (µS/cm): < 10,000
F (mg/l): < 1.1
Cr (µg/l): < 110
Mo (µg/l): < 55
V (µg/l): < 180
Chemical compoundAverage Value [%]Fe total19CaO47SiO₂12MgO2Al₂O₃1.6
The primary data represent iron and steel production in Germany.
The quality level of geographical representativity can be considered “good,” the quality level of technical representativity can be considered “good,” and the temporal representativity can also be considered “good.” Therefore, the overall data quality for this EPD can be classified as “good.”
To ensure comparability of results, only consistent background data from the ecoinvent database version 3.9.1 was used in the life cycle assessment (e.g. datasets for energy, transport, auxiliary and operating materials), which refer to the reference year 2022. The database is regularly reviewed and thus meets the requirements of EN 15804 (background data not older than 10 years). All consistent datasets contained in the ecoinvent database are documented and can be accessed in the ecoinvent online documentation.
For BOFS, only modules A1–A3 are declared since the material is integrated into other construction products (e.g., cement, concrete) and cannot be physically separated or identified at end of life. |
