Development of an innovative construction material and paving technology for the reuse of reclaimed asphalt in thick asphalt layers

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What is the project about?

The European Green Deal as well as the Fridays For Future movement have both helped to raise public awareness of the need for a more sustainable use of resources and their processing over the past 10 years.


Resources should be used sustainably using the Cradle to Cradle principles, which have been used for many years in a variety of businesses and may be justified economically as well as ecologically. The building sector has, however, made far too little efforts and developments in these fields over the years. Given that the construction sector, including the asphalt road construction which is the subject of this study project, is one of the industries that uses the most resources, there is a tremendous opportunity to contribute to protection of the environment.


The industry faces additional issues related to reducing energy usage and the corresponding CO2 emissions, as well as adhering to future aerosol limitations (starting in 2025). These obligations go beyond the requirement to maintain resources used in road building in the material cycle. Although asphalt is a highly recyclable substance, as shown by the long-term rise in recycling rates, the challenge of putting these ambitions into practice persists.

Photo by Matt Duncan on Unsplash

The Challenge

It takes a lot of energy to temper the raw components for making hot mix asphalt, particularly when recycled asphalt is included (bitumen, aggregate, reclaimed asphalt). To create a homogeneous mix and to guarantee workability and compactability during paving, high temperatures are necessary.

The next logical step towards a more environmentally friendly asphalt construction technique should therefore be to lower the temperature during the production process or to construct "cold asphalt layers" in addition to increasing the incorporation of reclaimed asphalt.


Traditional hot bitumens are unable to accomplish this, hence novel binders like the bitumen emulsions under consideration here must be utilized. However, bitumen emulsion use in Germany is restricted to just a few categories of application, despite the growing importance of ecological considerations (energy conservation, reduction of greenhouse gas emissions) and health protection (aerosols, burns). It has not yet been planned to use large asphalt layers or non-surface layers. This issue has already been addressed at the European level, as seen by the existence of the draft standard DIN EN 13108-31 [3], which outlines the specifications for emulsion-bound asphalt concretes.


However, this standard so far only lists empirical tests on which the new mixes will be categorized and described. Despite the fact that the binder is crucial in this situation, there isn't a bitumen emulsion specifically designed for this use. The bitumen emulsion basically lacks a reaction partner in the form of raw aggregates when asphalt granules are employed, which is often necessary to trigger the breaking of the emulsion. High void contents and any potential water inclusions also have a significant impact on the mechanical qualities of the asphalt layer, making it impossible or extremely difficult to open the road to traffic at all. Designing an emulsion-bound cold mix that enables the application of varying amounts of recycled asphalt in thick asphalt layers (> 4 cm) is the goal of this research project. The mechanical qualities of the final layer must be competitive with those of a traditional hot-bound asphalt layer in order to enable market establishment.

For this project, the ensuing sub-objectives were derived:

  1. Development of a new emulsion system that allows the use of reclaimed asphalt,
  2. Development of a mix composition specialized for the field of application,
  3. Development of new compaction methods using innovative microwave technology to remove the trapped emulsion water.

Ilmsen's task

Ilmsens GmbH, in collaboration with Synantik GmbH, is responsible for the microwave drying of asphalt. This assignment is part of sub-goal 3: "Development of novel compaction techniques based on revolutionary microwave technology to release trapped emulsion water." This work is broken into two halves. This is the microwave transfer and, as a novel component, the attempt to locate trapped water in the bitumen using Ground Penetrating Radar.

The Funding

This project is a joint project within the framework of KMU Innovativ: Resource Efficiency and Climate Protection in the Framework Program Research for Sustainable Development - FONA3

Grant on a cost basis of Federal Ministry of Education and Research

Project sponsor: Project Management Jülich

Duration: 01.08.2022-31.01.2025

Participating Partners: Synantik GmbH, BABIC GmbH, University of Applied Sciences Erfurt

Funding Code: 033RK105C