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.