Evaluation of the rheological properties and molecular distributions of asphalt binder under multiple aging and rejuvenating cycles (MARC)

Abstract

Because of the widespread use of reclaimed asphalt pavement (RAP), various recycling agents (RAs) are developed and used in pavement engineering nowadays to restore the properties of RAP in asphalt mixes. Whereas there are many RA products available, it remains unclear on the fundamental rejuvenation mechanisms behind different RAs and the selection method of proper RA product to restore these recycled materials properties. In addition, there are important questions on hold in terms of RAP repeated recycling and the continuity of restoration capacity from these RAs. Therefore, this study is designed to track the properties changes of the asphalt binders in the context of multiple aging and rejuvenating cycles (MARC). Three different types of RA products are selected and evaluated using rheological characterization and chromatography (molecular distribution) analysis. Results show that the beneficial effects from RAs degrade over time with increase of aging/rejuvenating cycles. Two oils with their molecules that are mainly distributed in the medium molecular size (MMS) range, which compensate the loss of the MMS molecules of the base binder due to aging, show the good effectiveness in restoring not only the complex modulus but also the phase angle of the aged asphalt. And the good correlations between phase angle and MMS as well as LMS proportion indicate the fundamental relationship between binder’s molecular distribution and its rheological properties.