Federal Highway Research Institute

Cold recycling

Testing the cold recycling construction method with foamed bitumen

Cold recycling offers the possibility to use up to 100 percent of reclaimed asphalt.

The photo shows a  mobile cold mixing plant (KMA) with bitumen and water tank Mobile cold mixing plant (KMA) with bitumen and water tank


In order to make transport and traffic systems more sustainable, resources should be used efficiently to reduce environmental influences and the required energy. Innovative ideas for the construction process are required. The topic of recycling is highly relevant to this context, in order to be able to take financial as well as environmental influences into account.

The photo shows the paving of the cold recycled layer on the duraBASt Paving the cold recycled layer on the duraBASt

Beside the methods for hot and warm recycling of asphalt, methods for cold recycling are seen as promising. They offer the possibility to use up to 100 percent of reclaimed asphalt. As the reclaimed material is not heated, therefore less energy is consumed and fewer emissions are produced.
In addition to small quantities of cement (to increase stiffness and moisture resistance), foamed bitumen is used as the main binding agent. After a short time from compaction, the resulting material can be used as a base course. According to the current state of the art, cold recycling construction is considered to be particularly useful in the downstream road network.


The photo shows the compaction of the cold recycled layer Compaction of the cold recycled layer

In addition to laboratory tests to prepare a recipe with the available materials, a test section is constructed on the duraBASt. The section has a total length of 100 meters, two thirds of that with the cold recycled material and one third with a standard reference material according to RStO, ZTV Asphalt & TL Asphalt.

The test section is accompanied by measuring equipment and instrumented with sensors (tem-perature, compressive stress and strain as well as humidity). Subsequently, accelerated loading will applied - in combination with non-destructive measuring systems - using the standardized APT (Accelerated Pavement Testing) program.


The main objective of the project is to gather empirical characteristic values for a cold recycled layer consisting of foamed bitumen and cement under real conditions in a large-scale accelerated load test with the MLS30 Mobile Load Simulator.

The picture shows the logos of the project partners