Performance Evaluation of Asphalt Pavement Mixes in Idaho Containing High Percentages for Recycled Asphalt Pavement (RAP)

Currently, Idaho Transportation Department (ITD) allows the use of high percentages of reclaimed asphalt pavement (RAP) in an asphalt mix after virgin binder grade is adjusted. However, it is imperative to ensure that RAP mixes can perform at least as well as virgin mixes. In response to this need, this study examined 2 classes of asphalt mixes (SP4 and SP5), which included a total of 10 mix designs with different percentages of RAP from 2 sources. The researchers evaluated mixes’ laboratory performance as well as AASHTOWare Pavement ME Design field performance predictions in terms of resistance to rutting, fatigue cracking, and low temperature thermal cracking. Generally, even after binder grade adjustment, the rutting resistance of RAP mixes increased with an increase in RAP percentage, indicating that the current practice of binder adjustment cannot account for the stiffening effect of RAP. The fatigue cracking resistance of the mixtures with a low percentage (i.e., 17 percent) of RAP was comparable to that of the virgin mix. However, the effects of high percentage RAP (more than 17 percent) on fatigue cracking depended on target PG of virgin binder. When the virgin binder is not polymer modified (e.g. PG 58-28), bumping down the grade of virgin binder did not affect the fatigue resistance of high RAP mixes, such as the case of North Idaho mixes. However, when the virgin binder is polymer modified (e.g. PG 70-28), bumping down the grade of virgin binder may lead to elimination or reduction of the degree of polymer modification which affects the fatigue resistance of high RAP mixes, such as the case of South Idaho mixes. The addition of RAP (either a low or high percentage) could adversely affect the thermal cracking resistance of RAP mixtures. The mixture’s volumetrics also affect the performance. The researchers recommend that a performance test for cracking should be included in the mix design; specifically, AASHTO T283-14, which can help determine both the moisture susceptibility and cracking performance of a mixture (i.e., indirect tensile fracture work density), should replace the current ITD moisture susceptibility test. The research team also recommends that fracture criteria for asphalt mixes should be developed by coring in-service pavements that exhibit both good and bad performance. Alternatively, empirical models and procedures were developed to design RAP mix without conducting performance tests which is worth validation in future study.


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  • Status: Completed
  • Funding: $189063.00
  • Contract Numbers:

    RP 213

  • Sponsor Organizations:

    Idaho Transportation Department

    P.O. Box 7129, 3311 West State Street
    Boise, ID  United States  83707-1129
  • Project Managers:

    Santi, Mike

  • Performing Organizations:

    University of Idaho, Moscow

    Office of Sponsored ProgramsNational Institute for Advanced Transportation Technology
    P.O. Box 443020
    Moscow, ID  United States  83844-3020

    Washington State University, Pullman

    Pullman, WA  United States  99164
  • Principal Investigators:

    Bayomy, Fouad

    Wen, Haifang

  • Start Date: 20120703
  • Expected Completion Date: 0
  • Actual Completion Date: 20160429
  • Source Data: RiP Project 32067

Subject/Index Terms

Filing Info

  • Accession Number: 01560836
  • Record Type: Research project
  • Source Agency: Idaho Transportation Department
  • Contract Numbers: RP 213
  • Files: RIP, STATEDOT
  • Created Date: Apr 23 2015 1:00AM