Rheological characteristics of paving bitumens and recycled binder blends in relation to ageing

The amount of produced asphalt mixtures incorporating reclaimed asphalt has been steadily increasing in the past years and so has the use of recycling agents. Some countries in Europe and elsewhere have already come into contact with repeatedly recycled materials. This study, therefore, investigated the influence of long-term ageing on multiple recycled binder blends and thereby simulated a repeated recycling process. In order to be able to understand the behaviour and well describe the characteristics of recycled binder blends, the obtained results were compared to the behaviour (results) of paving bitumens and reclaimed binders (binders extracted from Reclaimed Asphalt). Each binder group was then described by empirical tests as specified in the harmonised standard for paving bitumens (EN 12591) as well as by performance parameters for assessing long–term embrittlement such as viscoelastic temperature (VET) and the Glover–Rowe (G–R) parameter. It was found that recycled binder blends exhibited similar or higher penetration compared to paving bitumens upon recycling as well as after ageing, but the softening point shifted to a higher temperature domain. Likewise, reclaimed binders’ properties were rather similar to long-term aged paving bitumens than to recycled binder blends. Furthermore, it was confirmed that a strong correlation between VET and G–R exists although different binder groups manifested different durability thresholds. Additionally, a relationship was found between VET, G–R and softening point. It was proved that usage of empirical tests can in some cases provide asphalt engineers with equivalent information about binder rheology as modern functional parameters in case of non-modified binders.