Recommendations for Seal Treatment Rejuvenation Specifications Based on Bending Beam Rheometer Testing of Mixture Beams

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Recently, use of pavement preservation technologies, such as bituminous seal treatments, has increased. Seal treatments are often used to rejuvenate aged asphalt pavements and can decrease permeability and retard oxidation, cracking, and raveling. Many factors affect rejuvenation, and current specifications governing how rejuvenation is characterized could be enhanced. Viscosity testing of asphalt binder extracted and recovered from a pavement's near surface is the predominant means of characterizing rejuvenation (e.g., a product must reduce viscosity by 40% to be classified as a rejuvenator). This paper presents data that suggest other rejuvenation approaches are worth considering because (a) extraction and recovery can adversely affect viscosity results, (b) viscosity testing cannot be conducted without forced and unrealistic blending of aged binder and rejuvenator, (c) high test temperatures may not be the most informative for distresses of interest (e.g., cracking), and (d) viscosity could not detect rejuvenation behaviors of some proprietary products. Alternatively, this paper suggests rejuvenation specifications be developed with bending beam rheometer (BBR) testing of mixture beams sawn from laboratory-compacted asphalt surfaces (e.g., a product must increase the m-value by 0.040 to be classified as a rejuvenator). This approach has shown promise for viscosity testing, and many concerns about viscosity testing are alleviated with BBR testing. A specification approach that uses BBR testing of laboratory-compacted asphalt is described and recommended for rejuvenation characterization.