Mixing and compaction recommendations for warm mix asphalt (WMA) with recycled asphalt shingles (RAS) : final report.
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2017-05-01
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Edition:Final report
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Abstract:The use of recycled asphalt shingles (RAS) is an attractive option for asphalt mixture producers due to the
high amount of recycled asphalt binder available in RAS. By weight, RAS contains 10 to 25% asphalt by total
weight of the shingle. The asphalt binder in RAS is generally much stiffer than conventional paving asphalts due
to the requirements of the roofing shingle industry. This increase in asphalt binder stiffness generally results in a
stiffer asphalt mixture that is more difficult to compact in the field. Some asphalt mixture suppliers are looking at
utilizing warm mix asphalt (WMA) technologies to help with compaction, but still limited information exists on
the use of WMA with RAS and how the mixing and compaction properties are influenced.
With the transportation infrastructure industry moving towards sustainable technologies and recycling when
possible, the use of recycled asphalt shingles (RAS) in hot mix asphalt looks appealing. However, the handling
and performance of these mixtures is still highly questioned and viewed as potentially problematic by most
agencies.
A laboratory study was conducted to evaluate the impact on recycled asphalt shingles (RAS) on the
compactability of asphalt mixtures. Two different methodologies were utilized in the study: 1) Asphalt binder
based testing; and 2) Asphalt mixture based testing. In addition to the RAS, two different types of WMA
technologies were included to evaluate the change in asphalt compactibility. The results of the study showed that
performance grading of the RAS required the RAS to be blended with a much softer asphalt binder at varying
percentages; the inclusion of recycled asphalt shingles, whether it is Post Manufacturer or Post Consumer, will
detrimentally impact the mixing and compaction properties of the asphalt mixtures; and that the addition of
WMA technologies to the RAS asphalt mixtures does appear to aid in the compaction properties of the final
asphalt mixture.
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