Road construction in the interests of resource optimisation

Roads must be designed to withstand the impacts of traffic and climate for as long as possible. In addition to detailed planning, the most important factors influencing the quality – and thus the possible service life of a road – are the execution and selected construction materials. At the same time, ecological aspects such as resource and environmental protection must be taken into account. The challenge for municipalities, federal states and the federal government: to achieve the best result with limited resources.

Primary and secondary aggregates: a perfect match

As a matter of principle, product-neutral tendering is stipulated in the relevant procurement regulations. Fact is, that due to added environmental specifications, the possible use of secondary aggregates is limited compared to primary materials Environmental conditionstechnical requirements and the type of execution are influencing factors that have to be assessed in the tendering phase of each project. Due to the time and effort involved, tendering bodies tend not to formulate tenders in a product-neutral manner, so that only primary materials are permitted, and thus, execution with secondary raw materials is excluded.

But if the appropriate conditions are met, construction with secondary aggregates is just as safe and an economically interesting alternative to conventional construction with primary aggregates. Those who decide to use substitute building materials – often in combination with primary building materials – demonstrate commitment to reuse, resource conservation and climate protection.

IBA aggregates amend the natural aggregate sources

Use in road construction and earthworks

GRANOVA incinerator bottom ash is most frequently used as a substitute building material/secondary aggregate in road substructures as subgrade. Rarer and only permitted in selected road load classes, the material is used in the subbase, such as the frost blanket or lower base/base course in the road pavement structure.

Road construction with incinerator bottom ash aggregates in subgrade layer

Main application area of GRANOVA IBA in Germany: subgrade layer

Applications at a glance

Based on the specifications of the German Secondary Aggregate Directive (EBV) and the regulations of the Road and Transportation Research Association (FGSV), the possible applications for incinerator bottom ash are summarised on this page. The tables show the areas of application in the form of a traffic light system for the material classes HMVA-1 and HMVA-2 defined according to the EBV. A distinction is made between five cases depending on the local conditions.

  • Fall A 24

  • Fall B 24

  • Fall C 24

  • Fall D 24

  • Fall E 24

Additional information regarding the application tables:

  • The use of incinerator bottom ash in water protection areas of zone WSG I and II is not allowed.
  • The use of incinerator bottom ash in areas where the groundwater cover layer consists of gravel or coarse-grained material is not permitted; in this case, an artificial cover layer may be produced with the approval of the authorities.
  • HMVA-1 and HMVA-2 are subject to a mininum application volume of 50 and 250 m³ respectively. Exceptions apply for maintenance and supplementary measures.
  • When complying with the terms and conditions from the Secondary Aggregate Directive the use of recycled aggregates does not require permission under German water law.
  • Outside of water protection zones (WSG and HSG), authorities must be notified when using HMVA-1 and HMVA-2 in volumes exceeding 250 m³; in all other cases, the use must be documented.
  • Within water protection zones, incinerator bottom ash, like most secondary aggregates, are subject to a notification obligation, regardless of quantity and material class.
  • Version 01.2024

Realisation according to FGSV

When GRANOVA is used in the road subgrade, different construction methods can be used, whereby the core construction method is chosen most frequently. The Secondary Aggregate Directive stipulates that earthworks must comply with the FGSV bulletin “Leaflet on construction methods for technical safety measures for the use of soils and construction materials with environmentally relevant constituents in earthworks (M TS E)”.

An overview of construction methods can be found in our German Handbook on secondary aggregates.

Incinerator bottom ash road construction: Core design according to M TS E regulation

Example of the design of a dam with a core made of soil or construction material with environmentally relevant ingredients (principle sketch according to M TS E)

Advantages at a glance

The construction with GRANOVA is not only a sustainable option, but offers many other advantages:

  • high economic efficiency due compared to conventional construction
  • certified, technologically high-quality construction material
  • conformity with technical regulations for road construction and earthworks
  • proven environmental compatibility with the German Secondary Aggregate Directive
  • execution in accordance with the Circular Economy Act
  • conservation of primary construction materials