Effect of Ageing in Various Bituminous Mixes
Effect Of Ageing In Various Bituminous Mixes civil project report The aim of this paper is to explain phenomena associated with bitumen aging and establish design patterns that contribute to optimizing the aging resistance of bituminous mixes based on the rational addition of calcareous fillers (hydrated lime and limestone filler). The potential benefits of using fillers to improve aging resistance are well-known.
However, concepts related to the biphasic filler-bitumen system affecting some of the main characteristics of mixes are not always considered. In this paper, a new study procedure, “Universal de Caracterización de Ligantes” (UCL®), a method for haracterizing both conventional and polymer-modified binders developed at the Technical University of Catalonia, has been applied. In addition, rheological tests have been performed with the dynamic shear rheometer and non-routine procedures such as macromolecular analysis (e.g. gel-permeation chromatography and infrared spectroscopy).
From the results presented in this paper, the following conclusions can be drawn:
- Binders from roads of long time in-service generally display a low degree of age-hardening. Based on the rheological and conventional measurements, the estimated equivalent laboratory aging durations are much shorter than those being standardized;
- Low voids in the asphalt mixture and surface sealing and overlay can prevent aging of the binder;
- Aging kinetics and formation of sulfoxides and carbonyls are strongly temperature dependent. It is shown that the increase in bitumen stiffness correlates well with carbonyls formed on aging. For the SBS modified binder, the polymer is found to inhibit the formation of sulfoxides on aging;
- Compared to laboratory aging, much higher level of sulfoxides but lower level of carbonyls is found for the binders aged in the field. This suggests that oxidation mechanisms in the field may not be the same as in laboratory aging tests;