Aging of asphalt binders leads to damage on pavements, due to changes in their rheological behavior and in the binder composition. A hardening of the asphalt can be observed, mainly caused by the oxidation of the asphalt binder itself. Oxidation rate is influenced by temperature, ultraviolet radiation and intrinsic characteristics of materials. In order to be characterized, the binder is extracted from the field-aged asphalt cores that use to have several centimetres in thickness. The aging process, however, depends on the access of oxygen into the field core which varies with the distance from the pavement surface. In order to know the aging conditions of the pavement surface (only) and to evaluate their influence on the adhesion characteristics, it is necessary to recover the surface asphalt binder. Only the surface binder is exposed to ultraviolet rays and weathering. A new test method has been developed in this work. It is based on the asphalt binder recovery from the upper part of the asphalt mixture layer. This method was validated by the infrared spectrometry through comparison with the neat asphalt binder (aged and not aged) and with the conventional extraction. In addition, an accelerated aging protocol was developed with the use of a climate chamber comprised of brightness settings, and moisture and weather conditioning, to relate to the French climate. The aging results obtained in the laboratory and in the field were compared using the same test method. This comparison allowed the establishment of an accelerator factor with respect to the increase of sulfoxide and carboxyl groups. This study provides a better understanding of the influence of aging on the skid resistance and the ability of the material to resist to polishing.
Characterization of aging processes on the asphalt mixture surface