Ashes are transformed from waste into a civil engineering product

News 2021-11-01 at 9:18
© Ari Petäjistö

The technical properties of the ash granules produced by Ecolan Oy were tested in 2018–2019 during the construction of the Söörmarku junction in the City of Pori, Finland. Preparation of the test structure was carried out as part of the Circwaste project and the Peittoo area was used for intermediate storage of the material.

Since then, Ecolan Oy has continued the technical and commercial development of ash granules and has found a stable market position in civil engineering. Several projects are currently underway, such as the construction project of the Hämeenkyrönväylä highway 3 by Destia, which started in 2020.

Material made from industrial by-products

The ash material is commercialised as Ecolan Infra® TR, a granular aggregate that is lighter than natural sand and gravel and crushed stone. The ash granule is produced from industrial side streams and used in earthworks on the basis of the Government Decree on the Recovery of Certain Wastes in Earth Construction. The main raw materials in ash pellets are fly ash and bottom ash produced by the Finnish energy industry, which in Ecolan Oy's granulation process transforms from waste into a product suitable for infrastructure construction.

In the process developed by Ecolan, the ash is rotated with water in a drum to form a granulate, which, when separated into different sizes, is suitable for different construction sites. As a porous material, ash granules have a number of advantages for civil engineering: they are insulating, lightweight and compactible.

In many applications, ash granules compete with traditional stone materials and insulations in terms of properties and costs. For example, compared to plastic-based insulators used in civil engineering, it is possible to achieve significant cost savings with the use of ash granules.

Best suited for fairways, fields and foundations

The main applications of ash granules in civil engineering are the structural layers of fairways and fields, as well as the foundation structures of industrial and warehouse buildings. New uses and applications for ash are being explored, in particular in soil stabilisation, where fine ash is used. Ash granule is not suitable for groundwater areas or for residential construction. Similarly, ash cannot yet be used for the construction of motorways or highways.

In the field of road construction, material approval from the Finnish Transport Agency has been sought for ash, which is intended to standardise ash as a material for road construction approved by the Finnish Transport Agency. The approval process is still in progress.

Growing market for recycled materials

Ecolan Oy's sales of ash granules as lightweight aggregate products have developed positively. The company produces a total of 55,000 tonnes of ash at its production plants in Nokia and Viitasaari. The market is limited geographically to a radius of about 100 km from the production site, as transport costs largely determine the economic viability of using the material.

The prospects for the use of ash granules in earth construction are positive. Low-carbon targets now extend to construction, and customers are increasingly interested in the carbon footprint of the materials used.

As a material that meets the requirements of a carbon-neutral society, ash granule is largely a circular economy product. As a substitute for natural sand and gravel and crushed stone, ash enables the protection of sand and gravel ridges, which act as a filter for groundwater in Finland and contain irreplaceable natural values.

Ecolan Oy has the capacity to provide its customers with information on the life cycle carbon emissions of its products. The benefits are undeniable compared to many competing products. For example, a construction process based on Stabi80, a hydraulically-binding mineral binder, reduces CO2 emissions by one-sixth compared to the cement currently used.

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More information

  • Ari Petäjistö, Business Manager, Ecolan Oy,
  • Sami Leppimäki, Project Manager, Prizztech Oy,

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