William G. Buttlar
Glen Barton Chair in Flexible Pavements, University of Missouri
Research Engineer, University of Missouri
About the research
A comprehensive laboratory and field investigation was carried out to evaluate the performance of recycled asphalt mixtures in Missouri by researchers at the University of Missouri-Columbia, in collaboration with the Missouri Department of Transportation and the Midwest Transportation Center.
Eighteen field sections were evaluated, including a number of sections from the recent Long-Term Pavement Performance (LTPP), Special Pavement Sections (SPS-10) project in Osage Beach, Missouri, which was constructed in 2016. Binder testing and mix performance tests were carried out on field cores and laboratory compacted specimens.
Based on the findings of the study, the following conclusions were drawn: (1) Missouri’s practices for the responsible and effective use of recycled materials is sound and continues to improve over time. Recent mix designs demonstrate more appropriate balancing between recycled material levels and virgin binder selection, resulting in better performance tests results when compared to older recycled mix designs. (2) Opportunities exist for further improving recycled mix design methods and recycling optimization in Missouri, including (a) moving to higher asphalt binder replacement (ABR) levels, by implementing mixture performance tests (balanced mix design); (b) increasing the use of recycled ground tire rubber (GTR) in Missouri mixes, by using balanced mix design to certify mixes using new, more economical GTR recycling methods, and; (c) researching the use of recycled materials in stone-mastic asphalt (SMA) designs.
It is recommended to further evaluate and fine-tune mix performance tests for use in balanced mix design, which is particularly important for modern, heterogeneous recycled mixes.
Midwest Transportation Center
Missouri Department of
University of Illinois ($70,000.00)
Contract Number: DTRT13-G-UTC37