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Expert Task Group on Asphalt Mixtures & Construction; Asphalt Binders; and Models Technology September 2000 Attachment Q - Models Program Options

  1. Continue Superpave model development and accept two-year delay

    1. Advantages
      • Continues movement towards overall Superpave goals
      • Maintains research momentum
    2. Disadvantages
      • Extends overall Superpave completion date to 2007++
      • Adds 2-year gap to integrating mix design, PRS, and structural design
      • Effectively slows down implementation momentum.
    3. Assumptions
      • Further work on the Superpave models would be fruitful.

  2. Continue Superpave model development, accept two-year delay, but add adopting 2002 Design Guide models as interim step

    1. Advantages
      • Continues movement towards overall Superpave goals
      • Continues the integration of Mix Design Analysis, PRS and structural design
      • Maintains national momentum in Superpave models research and Superpave implementation
    2. Disadvantages
      • Extends overall Superpave completion date to 2007++
      • Adds $2- 3 million dollars to 2005 Plan estimate
    3. Assumptions
      • Further work on the Superpave models would be fruitful
      • Accuracy of 2002 models for Superpave work is acceptable

  3. Adopt 2002 Design Models for use with Superpave Mix Design Analysis and PRS, discontinue Superpave models research work, and include it in a 2003 Research Authorization request.

    1. Advantages
      • Estimates in the 2005 Plan remain roughly the same
      • Work is completed by 2005
      • Maintains national momentum in Superpave implementation
    2. Disadvantages
      • Loss in national momentum in Superpave models research
      • Would extend work to 2008++
    3. Assumptions
      • Accuracy of 2002 models for Superpave work is acceptable
      • 2003 Reauthorization Strategy is successful

  4. Eliminate Superpave models effort from 2005 Plan. Do not integrate 2002 Design Models with Superpave Mix Design and PRS. Suggest that further work be include in 2003 Research Authorization request.

    1. Advantages
      • Saves $4-6 million dollars in overall effort.
      • Allows further concentration on mix design, simple performance tester, and construction issues
    2. Disadvantages
      • Loss in national momentum in Superpave models research
      • Would extend work to 2008++
      • Adds 3++ year gap to integrating mix design, PRS, and structural design
    3. Assumptions
      • 2003 Reauthorization Strategy is successful

Expanded Discussion on using the AASHTO 2002 Design Guide Models (Ed Harrigan)

Use the 2002 design guide HMA performance models to complete a satisfactory, practical version of the Superpave system within the CY 2005 time frame.

  1. The development of the "next generation" materials characterization, pavement response, and distress performance models based on 3-D finite element analysis will require several years of work beyond 2005.

  2. There is a distinct benefit to providing the states with HMA mix, structural design methods and a PRS that share common models and test methods.

  3. The models admittedly don't yet represent the cutting edge of technology.

  4. One concern is that If the 2002 models are used in the Superpave system, the 2002 guide's materials characterization methods -- the ASTM dynamic modulus test perhaps supplemented with a repeated load deformation test and a fracture test - will need to be adopted as well. However, these same tests are proving to be good candidates for the Superpave simple performance tests.

  5. The present work in Task F of 9-19 to develop an advanced materials characterization test would become a part of the "next generation" model development, representing the beginning stage of a line of research extending into the more distant future.

  6. Once concern is that only limited calibration and validation of the models in the 2002 guide are possible with the funds available to Project 1-37A. Ideally, then, Superpave funds should be used to complete the full calibration and validation experiment.

  7. The results could also be used by AASHTO to upgrade the 2002 software. This course of action is planned for the fully validated version of the Integrated Climatic Model produced by Project 9-23.

If this option were accepted, the 2005 Superpave Plan would be changed as follows:

  1. The funds committed to adapting the 2002 models to the Superpave system and the HMA PRS are reduced to $500,000. Both objectives are accomplished in one project (new 2002-SP-01).

  2. A $1 million project is proposed for FY 2002 (new 2002-SP-02) to complete the validation of the 2002 performance models.

  3. The $400,000 project 2002-SP-02 (Materials Characterization Test: 1st-Article Design, Procurement and Testing) in the earlier versions is dropped.

  4. Project 9-28 is left in the plan although its results are no longer required to meet the 2005 deadline. If the committee adopted the overall strategy I am suggesting, we probably should add a new, long-term goal for orderly development of the next generation of models and transfer this project and 9-28 to it. (Though the committee may have little interest in pursuing such a goal).

 
Updated: 04/07/2011
 

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