Evaluation of New Asphalt Concrete Job Mix Formula Specifications

The North Carolina Department of Transportation (NCDOT) has recently modified the asphalt mixture design procedures in part, to increase the asphalt content and address observed cracking issues with asphalt mixtures. These changes have reduced the number of asphalt mixture types, changed compaction levels and the volumetric limits for some mixtures, and adjusted how recycled materials are considered. Given the complexity of the interactions between material parameters, the procedural changes do not guarantee that the resultant asphalt mixture designs have actually achieved the intended goal of improved durability. The proposed study will investigate how these recent changes have affected asphalt mixture designs with respect to composition and performance. A research study is needed because an understanding of how procedural changes like the ones enacted by the NCDOT affect the durability of asphalt mixtures under real world conditions does not exist. This research is also needed because; (1) mixture designs in North Carolina are performed by contractors and submitted to NCDOT for approval, which limits the control that the NCDOT has over how contractors interpret and use the mixture design procedures and (2) currently, the NCDOT does not incorporate cracking tests into their mixture design or mixture verification process; therefore, they must rely heavily on volumetric composition to ensure that durable mixtures are designed and used. With respect to these needs, the proposed research plan will achieve two objectives; (1) Compare and compile detailed comparisons of NCDOT approved asphalt concrete mixtures that were designed under the current and previous design procedures; and (2) Evaluate the impact of these changes on pavement performance.  Depending on the precise findings of this research, the primary outcome will either be confirmation that the updated NCDOT asphalt mixture design procedures have resulted in mixtures with improved durability or suggested additional changes that could achieve this goal. These outcomes can be used by the Materials and Test Unit of the NCDOT to improve asphalt mixture design, which will result in cost savings.


  • English


  • Status: Active
  • Funding: $91309
  • Contract Numbers:


  • Sponsor Organizations:

    North Carolina Department of Transportation

    Research and Development
    1549 Mail Service Center
    Raleigh, NC  United States  27699-1549
  • Managing Organizations:

    North Carolina Department of Transportation

    Research and Development
    1549 Mail Service Center
    Raleigh, NC  United States  27699-1549
  • Project Managers:

    Kadibhai, Mustan

  • Performing Organizations:

    North Carolina State University

    Department of Civil Engineering
    Raleigh, North Carolina  United States  27695
  • Principal Investigators:

    Underwood, Benjamin

  • Start Date: 20190801
  • Expected Completion Date: 20200731
  • Actual Completion Date: 0
  • Source Data: 2020-12

Subject/Index Terms

Filing Info

  • Accession Number: 01724928
  • Record Type: Research project
  • Source Agency: North Carolina Department of Transportation
  • Contract Numbers: FHWA/NC/2020-12
  • Files: RIP, STATEDOT
  • Created Date: Dec 11 2019 3:53PM