Mechanical recycling of EOL concrete into high-grade aggregates

• A new process for concrete recycling is developed in the context of the European C2CA project.
• The process aims to reduce the impact of construction and demolition waste by in situ mechanical recycling of EOL concrete.
• The process applies autogenous milling and ADR to extract high-grade 4–16 mm recycle aggregate from crushed concrete.
• Results show that the +4 mm recycled aggregate compares favorably with natural aggregate.

Recycling End of Life (EOL) concrete into high-grade aggregate for new concrete is a challenging prospect for the building sector because of the competing constraints of low recycling process cost and high aggregate product quality. A further complicating factor is that, from the perspective of the environment, there is a strong societal drive to reduce bulk transport of building materials in urban environments, and to apply more in situ recycling technologies for Construction & Demolition Waste. The European C2CA project investigates a combination of smart demolition, grinding of the crushed concrete in an autogenous mill to increase the liberation of cement mortar from the surface of aggregates and a novel dry classification technology called ADR to remove the fines. The feasibility of this recycling process was examined in a demonstration project involving 20,000 tons of EOL concrete from two office towers in Groningen, the Netherlands. Results show that the +4 mm recycled aggregate compares favorably with natural aggregate in terms of workability and the compressive strength of the new concrete, showing 30% higher strength after 7 days.