Federal Highway Research Institute


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StrUK: Road construction - Environmental protection - Circle economy

The picture shows the StrUK Logo

Planning, construction and operation of roads are subject to a wide range of requirements. In terms of volume, recycled construction materials, industrial by-products and processed soil material are the most important flow for the circle economy. These can and should be used in road construction as an alternative to natural building materials, also against the background of resource conservation and as a contribution to climate protection. Due to the possible quantities that can be used, the focus here is on unbound layers and earthworks. Seepage water can dissolve pollutants from building materials and introduce them into soil and groundwater. It is important to protect soil and groundwater.

In order to meet the requirements of soil and groundwater protection, a thorough knowledge of the seepage processes in the technical structures of road construction is necessary. For this purpose, the Federal Highway Research Institute operates and awards extensive research projects.

In addition, national and international committees are working towards the transfer of environmental protection requirements for road structures. In this context, solutions must be found to implement constructional and environmental requirements in a practice-oriented manner.

Topic waste - building material

More than 50 percent of the waste produced in Germany is construction and demolition waste. Of this amount, more than 50 percent is soil and stones. This waste can be used to a large extent. In this context, the term waste is a purely legal definition. Some construction and demolition waste is processed into recycled construction materials. Industrial by-products can also be used as building materials. This can save 15 to 20 percent of the aggregates required in Germany. From a regional point of view, transport distances for building materials can be minimized. An additional significant advantage of using these building materials is the saving of landfill capacity. It is currently not possible to landfill the entire volume of construction and demolition waste.

In terms of construction technology, recycled construction materials and industrial by-products are already an integral part of both international and national regulations. The road construction regulations for soils and stones are also being further specified with regard to efficient material flow management. This use of the above-mentioned construction materials has proven to be sensible in the last decades, both from a construction engineering and an environmental point of view.

Topic point seepage of road embankments

 The photo shows the lysimeter in Augsburg

During road construction measures, large masses are moved in earthworks. The basic principle of mass balancing is less and less applied today. The reasons for this include less new construction, more maintenance and expansion of federal highways and the fact that the principle of least interference with nature and landscape (instead of mass balancing) is followed when laying routes. Therefore, building materials are needed for the construction of earthworks. Recycling building materials, soil material or industrial by-products can also be used for this purpose. Soil from other construction sites in the vicinity can also be used (material flow management). In addition to the suitability for construction, the protection of soil and groundwater plays an important role in the selection of building materials. In order to guarantee this, it must be proven that no environmentally relevant constituents in relevant quantities can be discharged with the seepage water into the soil and groundwater.

2 pictures of the lysimeter Plant Lysimeter plant with quantity recording

The aim of the research work on the topic of seepage in road embankments is to be able to reliably estimate seepage water quantities in road embankments on the basis of reliable data. Hereby, instruments are developed to assess the effectiveness of different technical safety measures to minimize leachate quantities. The economically and ecologically optimized construction methods will increase the potential for the use of substitute construction materials in earthworks for road construction.

Since the infiltration of road embankments and the associated transport of environmentally relevant substances is a very complex issue, the work requires interdisciplinary cooperation between road constructors, hydrogeologists, geoecologists, mathematicians and chemists, among others, in order to solve the manifold problems.

Further Information