Cold recycling with foamed bitumen, gained knowledge from a test track in Germany

Abstract

During the recent years, the demand on more sustainable transportation infrastructure has increased considerably in the EU. In Germany the political goal is to become climate neutral by 2035. Among different solutions, recycling is an important approach to achieve circular economy for pavements as one of the main parts of transportation infrastructure. Cold recycling is a technique which needs less energy and has the potential of using higher rates of recycled material. The resulting material may not have the same characteristics as the conventional hot mix asphalt, but through an optimised mix and structural design, it is possible to construct pavements with the same or even higher durability than the conventional types but a greater potential for sustainability. In 2018 a research project on the topic of cold recycling with foamed bitumen was defined at Federal Highway Research Institute (BASt) in cooperation with the Wirtgen GmbH. The main goal of the project was to gather information and experience on the behaviour of cold recycled material with relatively low amounts of bitumen and cement, known internationally as Bitumen Stabilized Material (BSM). For this purpose, a 100-meter test section was built at the demonstration, investigation, and reference areal of BASt (duraBASt) with two different construction types (reference and cold recycled). Both sections were loaded with the Mobile Load Simulator (MLS30). This paper presents some of the results and findings from the non-destructive (FWD and rutting measurements) monitoring and tests on the extracted cores. The program proved that it is possible to design and construct pavements with the BSM and the comparable performance as conventional pavements in Germany.