University of Oulu developed earth construction granules for road sub-base layer

Pilot product: Earth construction aggregates for sub-base layer in road
Location: Oulu, Finland
Technology: Granulation with cement as binder
Ash type: Co-combustion bottom ash and fly ash
Ash content: Bottom ash 60%, fly ash 10%

This pilot demonstrated the feasibility of utilizing recovered fuel (SRF) and biomass co-combustion fly ash and bottom ash in the production of aggregates for earth construction, while meeting the legal leaching limits set by Finnish environmental legislation. The role of the ashes was to replace natural aggregate and part of the binder (Portland cement). Approximately 36 tons of ashes were used in the pilot production. The resulting 31 tons of granules were applied in the sub-base layer construction of a road located at the Välimaa waste management area in the city of Oulu, Finland.

The produced aggregates consisted of 60% bottom ash, 10% fly ash, and 30% Portland cement (by dry material content). This pilot highlights a sustainable pathway for reusing industrial side streams in infrastructure applications, contributing to circular economy and resource efficiency.

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