Fate of Polymers in Recycled Asphalt: a Multiscale Approach

Transport infrastructure represent the connecting network of our society. Whether motorways, country roads, cycle paths or sidewalks, the material asphalt plays a central role for mobility. Asphalt is usually a mixture of mineral aggregates of different sizes and an organic binder, bitumen. However, over time, both our society and the demands on our infrastructure have changed. Due to increasing traffic loading and more extreme temperatures, our roads have to withstand increasing loads under even more extreme climate conditions. In order to meet these requirements, the conventional bitumen binder is modified with so-called polymers. This mixture of bitumen and elastomers means that the binder in the asphalt can withstand higher loading and at the same time has a wide temperature-application range. The challenge of this polymer-modified bitumen is that the aging behavior of the polymer and bitumen is not yet understood on a fundamental level and therefore the issue of recycling cannot be answered effectively and efficiently yet. This represents the central questions and goals of this project: Understanding the aging of polymer- modified bitumen and transferring it from the molecular nano-bitumen level to the macro-asphalt level. This aging process should be simulated as realistically as possible in the laboratory and compared with actual field aging. As soon as the aging process is sufficiently understood, the issue of mixing old and new polymer-modified bitumen and the recycling behavior will be examined in more detail. The subject of rejuvenation is also dealt with in detail: how can we modify our material in order to restore it to its original state. The team from the Technische Universität Wien (TU Wien) is working on these questions in cooperation with the University of Antwerp (Belgium) and the Swiss Federal Laboratories for Materials Testing and Research (EMPA - Switzerland). The international, interdisciplinary team combines cutting- edge analysis methods from the fields of chemistry (spectroscopic and microscopic methods), civil engineering (mechanical methods) and machine learning. Various spectroscopic methods will provide information about the aging-induced changes in polymer-modified bitumen at the molecular level. These changes will be visualized on a microscopic level and transferred to the industry-typical characteristic values on a mechanical level. Machine learning is intended to meaningfully link the results from chemistry and civil engineering. The results of the project should enable polymer-modified bitumen to be treated in such a way that it can be meaningfully recycled. This will ensure sustainable resource usage in road construction in the long term.