Dominik Blasenbauer, Johann Fellner, Stefan Skutan, Jakob Lederer
Mixed demolition waste comprises concrete, stones, bricks, fine mineral fractions, and extraneous materials that can impair the quality of recycled aggregate. Upgrading this waste into high-quality building materials requires sophisticated dry-wet mechanical treatment. However, detailed analyses of material flows, energy use, and composition from such processes are scarce, though essential for LCA and economic assessments. Recycling outcomes also depend on local conditions, making the collection of primary data crucial. For Austria, existing studies are outdated or missing. This study investigates dry-wet mechanical treatment of mixed demolition waste at an Austrian facility. The process combines dry pre-treatment (screening, sorting, metal removal) with wet steps (washing, screening, density separation). A three-day sampling campaign revealed that 78% of the input material becomes high-quality recycled aggregates. Fines (21%) are used in cement production as a substitute for primary raw materials. Metals and impurities (1%) enter recycling or waste-to-energy streams, with no landfill fraction. The final product, a standardized 0/16 aggregate mix, meets environmental standards and achieves end-of-waste status under Austrian law. Wet treatment reduces non-mineral impurities by ~40% compared to dry treatment and improves grading curves by removing fines. Chemical analysis confirms this, as washing transfers oxides and minerals from fines to the filter cake. A simplified economic analysis indicates that gate fees and product trading are the primary revenue drivers. Future work builds on the data assessed and uses it as a basis for a comprehensive life cycle and economic analysis. • MFA assesses the material flows and operational data of an Austrian CDW plant • Dry-wet mechanical treatment of CDW removes impurities, yielding high-quality aggregates • The process efficiently separates impurities and fines