United States Department of Transportation
i
Modeling the performance properties of RAS and RAP blended asphalt mixes using chemical compositional information.
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2017-01-01
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[PDF-5.06 MB]
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Abstract:Reclaimed asphalt pavement (RAP) and recycled asphalt shingles (RAS) can improve the sustainability of asphalt concrete (AC) due to cost savings and environmental factors, but it is necessary to ensure that pavement performance is not compromised. To study the effects of aging and increasing asphalt binder replacement levels, chemical characterization and rheological properties of binders from various sources were investigated. Binders from five ACs designed with varying ABR percentages (0% to 60%) were recovered using the standard Rotovap test procedure. The base binder used in the AC design and binders recovered from RAP and RAS were also tested. In addition to standard aging protocols, base binders were subjected to a second pressure aging vessel (PAV), whereas one PAV was applied for the extracted binders. Rheological parameters for low‐temperature cracking susceptibility and block and fatigue cracking derived from dynamic shear rheometer (DSR) and bending beam rheometer (BBR) tests appeared to have consistent trends with aging and increasing ABR levels. These parameters are helpful in evaluating progression in brittleness of binders with ABR and aging. It was concluded that AC with ABR levels above 20% could suffer from short‐ and long‐term cracking potential. Aging happens as a result of oxidation, which can be seen by an increase in carbonyl and sulfoxide components and larger molecular size components such as resins and asphaltenes. The difference in chemical composition of binders aged via rolling thin‐film oven (RTFO) and PAV is small, but this gap increases on double PAV. It was also observed that the double‐PAV binders have a chemical composition similar to those with a higher content of reclaimed binders. Asphalt concrete with high ABR content can be at an already critically aged condition immediately after production; moreover, aging progresses much faster in the binders of such mixes.
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