Long-Term Aging Performance Analysis of Oil Modified Asphalt Binders

Oil modification of asphalt binders is a widely adopted strategy for meeting low temperature performance grade (PG) specifications. There is no shortage of data characterizing the rheological benefits of several oil modifiers. Current AASHTO M320/M332 specifications evaluate low-temperature performance using the bending beam rheometer which measures creep stiffness and relaxation properties of the asphalt binder after 20h of aging using a pressure aging vessel (PAV). In this study, extended aging effects on oil and polymer modified binders are investigated using three oil-modified binders compared against a control binder using PG and PG+ testing methods. The oils evaluated include bio-oil and re-refined engine oil bottoms. All binders were subjected to a rolling thin film oven and 20-h PAV aging, as well as extended PAV aging of 40 and 60h. Binders are evaluated using multiple stress creep recovery, AASHTO TP123 dynamic shear rheometry elastic recovery, and linear amplitude sweep tests in addition to standard PG methods. The results show that many of the rheological benefits supplied by the oils tend to diminish after 40h of PAV aging. However, the long-term effects depend greatly on the type of oil used, as well as the type of polymer modification used. The results suggest that 20-h PAV aging may not be sufficient to predict the long-term performance of the binder, and that extended aging periods (40-h PAV aging) should be considered when selecting oil modified asphalts.