Validation of Gyratory Mix Design in Iowa Phase II

As a result of the Phase I Study, the N specifications were changed in October 2016. In addition to the mix design changes, the Iowa DOT has implemented new asphalt binder grading criteria. Phase II is primarily a validation study of the new mix design specifications. The first objective of Phase II is to evaluate performance of the field mixes produced with the 2016 specifications to ensure performance expectations are being met for rutting, moisture susceptibility and low temperature cracking; both loose mix and cores will be sampled for subsequent testing. The second objective is to evaluate the new mix design specifications in terms of performance and constructability. A mix design analysis for each of the new ESAL levels using the source aggregates and binder from the field construction projects will be re-evaluated in mixture design. The N design will be validated using traditional mix design procedures by varying asphalt content to compact to 4% air voids. Measuring strength in the design process will directly correlate N design with performance tests. The third objective of the study entails performance testing of each mix at the optimum binder content in a given N design level using such tests as the dynamic modulus, Hamburg wheel track device, and disk-shaped compact tension to evaluate the stiffness, rutting moisture susceptibility and resistance to low temperature cracking. The results of this study will provide detailed information either verifying current N design levels in Iowa or give recommendations on how N design can be improved based on performance testing data and N design correlations with field density. The results will also show how changes to N design will impact rutting and mixture stiffness as well as predicted pavement performance. Phase II will be conducted as a laboratory study with the goal of addressing the mix design process and identifying how changes in N design will influence performance over a pavements lifetime. Tasks include: Task 1 - selection of projects, collection of materials and cores, and volumetrics evaluation. Task 2 - Evaluation of optimum asphalt contents for different N design values at three traffic levels. Task 3 - Comparison of new and old specifications through performance testing and analysis. Task 4 - Analysis and evaluation of performance test results in Pavement-ME. Task 5 - Development of final report.


    • English


    • Status: Active
    • Funding: $250000
    • Contract Numbers:

      Addendum 642


    • Sponsor Organizations:

      Iowa Department of Transportation

      800 Lincoln Way
      Ames, IA  United States  50010
    • Managing Organizations:

      Iowa State University, Ames

      Center for Transportation Research and Education
      2711 South Loop Drive, Suite 4700
      Ames, IA  United States  50010-8664
    • Project Managers:

      Goetz, Vanessa

    • Performing Organizations:

      Iowa State University, Ames

      Center for Transportation Research and Education
      2711 South Loop Drive, Suite 4700
      Ames, IA  United States  50010-8664
    • Principal Investigators:

      Williams, Chris

    • Start Date: 20180315
    • Expected Completion Date: 20200630
    • Actual Completion Date: 0

    Subject/Index Terms

    Filing Info

    • Accession Number: 01662940
    • Record Type: Research project
    • Source Agency: Iowa Department of Transportation
    • Contract Numbers: Addendum 642, TR-742
    • Files: RIP, STATEDOT
    • Created Date: Mar 19 2018 11:52AM