A Field Review: Successful Practices and Lessons Learned When Using Reclaimed Asphalt Shingles in Asphalt Mixtures
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The use of reclaimed asphalt pavement (RAP) and reclaimed asphalt shingles (RAS) in asphalt mixtures can provide initial cost savings through the replacement of a portion of the aggregate and virgin asphalt binder in a mixture for use in highways and trails. This keeps the reclaimed material from being discarded in landfills. Improvements in mixture design and materials processing and handling have increased the amount of RAP and RAS that can be used in asphalt mixtures today. The performance history of RAP mixtures over the past 40 years and RAS over the past 20 years, when properly engineered, produced, and constructed, can provide comparable levels of service as asphalt mixtures with no reclaimed materials, referred to as virgin asphalt mixtures. However, in some cases durability of asphalt mixtures containing RAS has been poor. Additionally, agency rationale for using RAS can be for very different reasons with different goals. Field visits of six agencies regularly using RAS in asphalt mixtures took place in the Summer of 2019. This effort showed that agencies with detailed policy and specifications on RAS use had the best control and performance. Field performance reviews of in-service pavements up to 9 years old containing RAS or RAP and RAS revealed that with appropriate policy, mixture design and control of quality, good performance can be obtained. This was typically obtained through the following comprehensive steps: 1) regular and diligent review of specifications and mixture design procedures, 2) monitoring pavement performance, 3) working with industry and 4) performing research as a basis for changes.