UC Davis

In this research, field slab samples were taken from an asphalt pavement in a hot climate with a design life of 40 years at 2, 4, and 7 years of pavement age to determine aging behavior with time at different depths. The asphalt binders were extracted and recovered to evaluate the aging and fatigue performance of the intermediate layer of the asphalt pavement. The chemical and rheological aging properties of the binders were evaluated using Fourier transform infrared spectroscopy and a dynamic shear rheometer, respectively. The pavement included 25 mm (1 in.) open-graded and 75 mm (2 in.) polymer-modified layers over three intermediate layer lifts. The intermediate layer aging is mostly governed by the connecting air voids and binder content of the asphalt mixes. The variation in aging deeper than 100 mm (4 in.) below the pavement surface was minor because of the absence of heat and access to air, with similar aging parameter values observed for different years of field sampling indicating little to no aging after construction. A good correlation ( R2 values of 0.79–0.92) was observed between the chemical property (carbonyl index) and rheological properties of the extracted binder for the dense-graded asphalt concrete layers between 25 and 100 mm depths. The fatigue performance of these extracted binders was evaluated by performing linear amplitude sweep tests. The results indicate that binder fatigue performance initially improved with moderate levels of aging but started to decline under extreme aging conditions.