United States Department of Transportation
i
Rejuvenator Laboratory Characterization and Field Performance
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2019-10-01
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[PDF-12.57 MB]
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Edition:Implementation Report,: September 2014–August 2019
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Abstract:Recycled materials including reclaimed asphalt pavements (RAP) and recycled asphalt shingles (RAS) have been widely used in asphalt mixes in Texas with at least three benefits: reducing construction cost, conserving raw materials and environment, and improving rutting resistance. However, there are two major concerns over the use of RAP and RAS: variability and premature cracking. This project addressed these two concerns. This project developed and disseminated the best practices of processing RAP and RAS through teaching four regional workshops. Additionally, researchers evaluated many bio-rejuvenators to improve cracking resistance through a series of laboratory testing and the construction of 17 field test sections. The bio-rejuvenators performed differently in the laboratory and field test sections, and some are more effective than others. Both laboratory and field test results indicated the total fatty acid content is a performance indicator for bio-rejuvenators, and the larger fatty acid content, the more effective the bio-rejuvenator. To perform well, bio-rejuvenators should contain more than 97 percent fatty acid content and less than 50 percent saturate fatty acid. Meanwhile, it is preferred to have the mass loss of less than 5 percent after the rolling thin film oven test. This project also recommended and demonstrated a four-step balanced mix design process for designing mixes containing RAP/RAS and rejuvenators: 1) selection of rejuvenator type, 2) determination of the range of the rejuvenator amounts required to meet both the binder specification and aging characteristics, 3) determination of the range of the rejuvenator amounts required to meet mixture rutting and cracking requirements, and 4) selection of final rejuvenator amount based on engineer judgement. Additionally, it is feasible to use the dynamic shear rheometer with 50 mm parallel plates to measure dynamic viscosity of bio-rejuvenators.
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