The “R‑Beton – Ressourcen schonender Beton – Werkstoff der nächsten Generation” project, funded by the BMBF under the HighTechMat Bau program, investigates the environmental performance of recycled concrete (R‑Beton) and its constituent materials. The study focuses on cumulative release of inorganic and organic substances after 64 days of exposure, comparing the results with the limits set by the German Environmental Protection Act (ABuG) and the DIB17 regulation.

Technical Results
Table 20 summarizes the cumulative releases (mg m⁻²) for a range of elements. The R‑Beton specimens consistently exceeded the DIB17 limits for several parameters, while the reference concrete and concrete with R‑cement remained within bounds.

Chloride: 14 479 mg m⁻² (limit 275.5 mg m⁻²) – 52‑fold exceedance.
Sulfate: 8 312 mg m⁻² (limit 264.5 mg m⁻²) – 31‑fold exceedance.
Antimony: 0.292 mg m⁻² (limit 5.5 mg m⁻²) – well below limit.
Arsenic: <0.64 mg m⁻² (limit 0.695 mg m⁻²) – within limit.
Barium: 40.9 mg m⁻² (limit 7.7 mg m⁻²) – 5‑fold exceedance.
Lead: 0.789 mg m⁻² (limit 7.7 mg m⁻²) – within limit.
Boron: 2.08 mg m⁻² (limit 813 mg m⁻²) – far below limit.
Cadmium: <0.064 mg m⁻² (limit 0.56 mg m⁻²) – within limit.
Chromium: 0.741 mg m⁻² (limit 7.7 mg m⁻²) – within limit.
Copper: <0.080 mg m⁻² (limit 15.4 mg m⁻²) – within limit.
Molybdenum: 10.78 mg m⁻² (limit 38.6 mg m⁻²) – within limit, but 2.9‑fold higher than reference.
Nickel: <0.243 mg m⁻² (limit 15.4 mg m⁻²) – within limit.
Mercury: <0.0066 mg m⁻² (limit 0.22 mg m⁻²) – within limit.
Selenium: <0.064 mg m⁻² (limit 7.7 mg m⁻²) – within limit.
Thallium: 1.05 mg m⁻² (limit 0.88 mg m⁻²) – slight exceedance.
Vanadium: 1.00 mg m⁻² (limit 4.4 mg m⁻²) – within limit.
Zinc: 63.9 mg m⁻² – no limit specified, but markedly higher than reference.

Inorganic releases of chloride and sulfate increased with the addition of recycled aggregate, yet remained below the statutory thresholds. The pronounced rise in molybdenum release (factor 2.9) is attributed to the displacement of molybdate by chromate in the cement matrix, as suggested by the literature on ettringite formation. Thallium, not intentionally added, also showed elevated release due to the high thallium content (≈ 4 mg kg⁻¹) of the CEM I cement used, exceeding the average German cement value by more than tenfold.
Polycyclic aromatic hydrocarbons (PAK) are not regulated by DIB17. Nevertheless, the R‑Beton with the RG2 aggregate released 7.05 mg kg⁻¹, surpassing the provisional limit of 25 mg kg⁻¹. This indicates that the current permissible content for recycled aggregates may be insufficient to guarantee environmental safety.
Screening tests based on the DIN 4226‑101 10:1 shake test were correlated with the long‑term release measured in the Dynamic Soil Leaching Test (DSLT). The strong correlation suggests that the shake test can reliably predict the leaching behaviour of R‑Beton, providing a practical tool for early assessment.

Collaboration
The project is a consortium effort involving the Institute for Building Research at RWTH Aachen, HeidelbergCement AG, and the German Federal Institute for Materials Research and Testing (DAMTP). HeidelbergCement has undertaken a subcontract to further investigate PAK leaching from R‑Beton, while the DAMTP has requested an additional study to refine the regulatory limits for recycled aggregates. The consortium’s integrated approach covers material production, processing, component and system development, and field application, aligning with the European directive for a “recycling society.” The collaborative framework ensures that scientific findings are translated into industry‑ready solutions, supporting the broader goal of reducing construction waste and enhancing resource efficiency in urban infrastructure.