The Minnesota Department of Transportation (MnDOT) joined TPF-5(213) as a state partner and co-researcher in 2009. MnDOT has been a national leader in the use and research of recycled asphalt shingles (RAS). MnDOT began researching the use of post- manufacturers RAS in hot-mix asphalt (HMA) over 20 years ago and developed their first specification allowing the use of post-manufacturers RAS in 1996. In 2003 MnDOT began researching the use post-consumer RAS and completed several demonstration projects in partnership with local government entities. In February 2010 MnDOT released provisional specifications allowing for the utilization of post-manufactured and post-consumer RAS up to 5% in both surface and base mixes for plant asphalt mixtures produced under Specification 2360 (Plant Mixed Asphalt Pavement).
In 2008 MnDOT completed a demonstration project at MnROAD, a National Research and Technology Center for cold weather road research, located in Albertville (40 miles northwest of the Twin Cities). The project utilized post-manufactured and post-consumer RAS in place of the recycled asphalt pavement (RAP) in mixes for several cells on the mainline shoulders and transition areas of the I-94 test track carrying interstate traffic. The RAS only and RAP only mixes were analyzed for asphalt binder and mixture properties. In February 2010, MnDOT published the report , “Incorporation of Recycled Asphalt Shingles In Hot-Mixed Asphalt Pavement Mixtures”, to summarize the research results of the testing completed on the MnROAD project along with extensive laboratory testing completed on previous demonstration projects. Field evaluations of in service RAS/RAP HMA pavements were also completed. The study addressed verification of the AASHTO 70% new asphalt binder to total asphalt binder criteria for RAS/RAP mixtures, observations on: the effects of RAS/RAP on HMA mixture durability; possible differences in performance between post-manufactured and post consumer RAS mixtures; effects of "softer binder in RAS/RAP mixtures; effects of different RAP sources; and the differences between lab produced and plant produced HMA mixtures.
MnDOT will be collecting and testing additional samples from this demonstration project for the TPF-5(213) study to expand their research on low temperature cracking and variations in pavement performance for post-consumer RAS, post-manufacturers RAS and RAP only mixes in HMA.
Jim McGraw, Chemical Lab Director
Greg Johnson, Assistant Bituminous Engineer
Ph: (651) 366-5464