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MnROAD | NRRA | Structure & Teams | Flexible Team

Standardization of SIP Calculation for Hamburg Wheel Tracking Test

Status: Active
Contract #: 1036333-WO08

Project objectives

The Hamburg Wheel Tracking Test (HWTT) is one of the most popular laboratory tests used by state highway agencies (SHAs) to evaluate the rutting resistance of asphalt mixtures. Because the test is conducted in water it also allows the evaluation of moisture susceptibility based on the stripping inflection point (SIP). According to AASHTO T 324, SIP is determined graphically as the intersection of slopes of the two fitted lines to the creep and stripping phases of the HWTT curve. Although the definition of SIP is straightforward, accurately determining SIP can be challenging because HWTT data do not always provide well-defined SIP, especially those with a marginal stripping failure. Over the years, HWTT equipment manufacturers and asphalt practitioners have developed different methods for calculating SIP, but they do not always yield the same results. The lack of standardization for SIP calculation could cause unnecessary disputes for SHAs when evaluating the HWTT results for mix design approval and production acceptance. This proposed project aims to develop HWTT analysis software to standardize and automate the calculation of SIP, which allows SHAs to make the most informed and undisputable decisions on the HWTT results. The software will be compatible with different HWTT devices to enable direct reading and processing of the raw data files without subjective data manipulation and interpretation.

The objective of the project is to develop HWTT analysis software to standardize and automate the calculation of SIP for evaluating the moisture susceptibility of asphalt mixtures. This software will be highly beneficial to SHAs currently using HWTT or considering implementing the HWTT for asphalt mix design and production acceptance.

Project tasks

Task 1: Information gathering

A survey of SHAs and HWTT equipment manufacturers will be conducted to summarize the different SIP calculation methods. Each method will be critically reviewed to identify its advantages and disadvantages. Based on the review results, the most robust SIP calculation method (in terms of calculation accuracy, consistency, and practicality) will be selected to proceed with software development in Task 2.

Task 2: Software development

Up to 100 existing data files will be collected from HWTT equipment manufacturers participating in the study. The files will be divided into three groups: results with a notable stripping failure; results with a marginal stripping failure; and results without a stripping failure. Each data file will be manually processed to calculate the SIP using the method selected in Task 1, and the results will be used as the reference to cross-check the software calculation results. In addition to the software, a user manual containing step-by-step instructions and illustrative calculation examples will also be developed.

  • Deliverable: An online meeting with the Technical Advisory Panel (TAP) to demonstrate the software and user manual.

Task 3: Software beta testing

The software and the user manual developed in Task 2 will be distributed to NRRA agency members using HWTT (including the California, Iowa, Illinois, Missouri, Montana, North Dakota, and Wisconsin DOTs) for beta testing. A web meeting will then be conducted with these agencies to collect their feedback, which will be used to finetune and troubleshoot the software for improvement.

  • Deliverable: An online meeting with the TAP to demonstrate the updated software after beta testing.

Task 4: Software release, final report, and NRRA webinar

Upon TAP approval, the updated software after beta testing in Task 3 will be released for public use. The software is anticipated to be operated on the Auburn University network, with access permission managed by NCAT and NRRA. A final report will be submitted to document the project’s research efforts and outcome. Finally, an NRRA Research Pays Off webinar will be conducted to introduce the software and user manual.

  • Deliverables: 1) software release, 2) a final report, and 3) an NRRA Research Pays Off webinar.

Project team

Email the Project Team
Principal Investigators: Fan Yin, f-yin@auburn.edu and Chen Chen, czc0105@auburn.edu, National Center for Asphalt Technology at Auburn University
Industry Partners: InstroTek, Inc., Pavement Technology, Inc., and Troxler Electronic Labs, Inc.
Technical Liaison: Dan Kopacz, Wisconsin DOT, Daniel.Kopacz@dot.wi.gov
Project Technical Advisory Panel (TAP): Contact us to join this TAP

  • Ashley Buss, Iowa DOT
  • Elie Hajj, University of Nevada - Reno
  • Dan Kopacz, WisDOT (TL)
  • Oak Metcalfe, Montana DOT
  • Derek Nener-Plante, FHWA
  • Joseph Podolsky, MnDOT
  • Michael Vrtis, MnDOT
  • Will Warfel, Illinois DOT
  • Tyler Wollmuth, NDDOT

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