Evaluating the Effects of Recycling Agents on Asphalt Mixtures with High RAS and RAP Binder
More than 90 percent of highways and roads in the United States are built using hot-mix
asphalt (HMA) or warm-mix asphalt mixtures, and these mixtures now recycle more
than 99 percent of some 76.2 million tons of reclaimed asphalt pavement (RAP) and about
1 million tons of recycled asphalt shingles (RAS). According to the National Asphalt Pavement
Association, cost savings in 2017 totaled approximately $2.2 billion with these recycled
materials replacing virgin materials.
The use of RAP in HMA dates back to the early 1900s, with renewed focus on research and
implementation in the 1970s and 1980s and again in 2008 with significant increases in the cost of
petroleum products including asphalt binders. Thus, highway agencies and the paving industry
have developed a renewed interest in utilizing larger quantities of recycled materials (RAP and
RAS) to maximize economic and environmental benefits that include conservation of natural
resources (aggregate, binder, fuel, etc.), reduction in energy consumption, and reduction in
emissions (including greenhouse gases).
In spite of these symbiotic benefits, state departments of
transportation limit the use of RAP and RAS in asphalt mixtures for reasons that include
variability of the recycled materials and concerns about long-term mixture performance. In
addition, mix design is more complicated and more time consuming, particularly with large
quantities of recycled materials identified by high recycled binder ratios (RBRs).
This pre-publication draft of
NCHRP (National Cooperative Highway Research Program) Research Report 927: Evaluating the Effects of Recycling Agents on Asphalt Mixtures with High RAS and RAP Binder focuses on using
recycling agents to facilitate increasing RBR.
This Summary Last Modified On: 9/27/2019