Rheological evaluation of asphalt blends at multiple rejuvenation and aging cycles

Abstract

The use of recycling agents has become a common practice to produce asphalt mixtures with high contents of reclaimed asphalt materials. Previous studies have shown that characterisation of rejuvenated asphalt blends using empirical tests, used for evaluation of ordinary bituminous binders in accordance with EN 12591, might not be sufficient. It was also proven that if the aged binder is restored in one parameter such as penetration or softening point, it does not necessarily mean that the other rheological properties are restored in the same way. For this reason, this paper characterises the behaviour of rejuvenated asphalt blends using two rheological parameters: the Glower-Rowe (G-R) parameter and the difference between the low-temperature continuous performance grades determined from the bending beam rheometer (BBR) stiffness and m-value criteria (ΔT_c). Recycling agents were added to an artificially aged asphalt binder. The first rejuvenation cycle of rejuvenation refers to 4 aging stages: no aging, rolling thin film oven test (RTFOT) aging, RTFOT combined with pressurised aging vessel (PAV) and RTFOT combined with two consecutive PAVs. In the second rejuvenation cycle, additional recycling agents of the same origin were added to the aged rejuvenated asphalt blends from the first rejuvenation cycle. The blends were then subject to further RTFOT aging and combined RTFOT and PAV. The obtained results showed that some rejuvenated asphalt blends did not satisfy the suggested threshold values set in literature for the G-R and ΔT_c parameters after long-term aging in the first rejuvenation cycle, and that most rejuvenated asphalt blends in the second cycle of rejuvenation did not meet the performance requirements after 20 h of PAV aging.

Keywords:

• multiple recycling
• rejuvenation
• aging
• recycling agents
• performance parameters (G-R, ΔT_c)

Acknowledgements

This paper was prepared with the support of the Czech Technology Agency, project TJ01000248 “Recycling agents for the extension of pavement lifetime with the use of a higher amount of Reclaimed Asphalt Pavement materials”.