Evaluation of a Surface Mixture with Delta-S Rejuvenator on NCAT Pavement Test Track

Abstract

Recycled materials have been commonly used in asphalt mixtures because of their economic, environmental, and social benefits. Reclaimed asphalt pavements (RAP) and reclaimed asphalt shingles (RAS) are the main sources of recycled binder in asphalt mixtures, but their use has been limited to low proportions. The main concern with the use of higher contents of recycled materials in asphalt mixtures is that the resulting pavements could be more susceptible to distresses associated with aged binder. The higher potential for the occurrence of these distresses could ultimately result in higher pavement maintenance and rehabilitation costs. Rejuvenators are said to address these problems by restoring the properties of aged binders in mixtures that contain higher proportions of recycled materials. The objective of this study is to evaluate the effects of a bio-based rejuvenator, called Delta-S, on the laboratory properties and field performance of asphalt mixtures. The National Center for Asphalt Technology (NCAT) built a section on the NCAT Pavement Test Track for the 2015 Research Cycle using a high RAP surface mixture with Delta-S. This mixture was subjected to a series of laboratory performance tests to determine the performance grade of the extracted binder, rutting and moisture susceptibility, stiffness, and cracking resistance. Field performance data from the Test Track were also obtained. The laboratory properties and field performance data were analyzed and compared with three other sections of the Test Track built with surface mixtures of different material characteristics. Results of the study indicated that Delta-S did not have any negative effects on ride quality or rutting performance of the mixture. The laboratory cracking performance for the mixture with Delta-S was generally lower than a mixture with similar gradation and a softer virgin binder, although field performance could be considered similar. Still, Delta-S gave the mixture performance properties close to those of a mixture with less RAP contents. In summary, Delta-S may be considered a viable alternative for asphalt mixtures with high RAP contents, and continuing evaluation of the Delta-S mixture is recommended on the Test Track.