Cracking resistance evaluation of asphalt binders subjected to different laboratory and field aging conditions

The ability of the Pressure Aging Vessel (PAV) to properly simulate the long-term aging characteristics of asphalt binders has been questioned by researchers in the recent years. Several research efforts have indicated that the current PAV protocol may age the materials significantly less severely than the actual environmental field agents. Alternatively, updates on the current PAV testing procedures have been proposed to age the binders for 20 or even 60 h beyond the current 20 h. A protocol with very thin binder films, named as Universal Aging Test, has also been recommended by the Western Research Institute. Thermal aging with the combination of ultraviolet radiation exposition and heating has also been regarded as a possible more realistic route. This work aims to evaluate the cracking characteristics of nine unmodified and three modified (by SBS, ground tire rubber, and TLA) asphalt binders aged by different testing methodologies, i.e. a thermal route with changing exposition times and an ultraviolet route. The carbonyl index and the benzylic hydrogen content obtained by Fourier Transform Infrared Spectroscopy and Nuclear Magnetic Resonance, respectively, were evaluated to identify the chemical effects of the different aging strategies. The cracking resistance of the aged binders was evaluated by means of the Glover–Rowe (GR) parameter and of LAS test results. The GR results showed that the critical block-cracking zone could be reached by the two routes, being the oxidative effect that happens in the field more evident in the UV radiation route. Larger values of the benzylic hydrogen were observed for the materials deriving from a deasphalting residue process, resulting in higher susceptibility to aging. The carbonyl index was very sensitive to UV aging and presented in general larger values than the other aging strategies. The presence of an elastomeric modifier apparently protected the SBS and GTR samples against UV aging.