Pilot Implementation of the Overlay Tester and Double-Blade Saw

Past experience and recent field performance data has shown that several of Texas Department of Transportation’s (TxDOT’s) widely used asphalt mixtures are rut resistant but increasingly prone to cracking. Under Research Project 0-4467 the Overlay Tester (OT) was successfully demonstrated as a simple performance-related test to identify the crack resistance of asphalt mixtures. This implementation project focused on developing specifications for the OT, purchasing three units, and conducting shakedown tests on the new units. Within lab testing at the Texas Transportation Institute produced very consistent results. However, variability problems were encountered in the initial Round-Robin tests between labs. An investigation was conducted to identify the source of the differences. Several factors were identified and these are described in this report. Recommendations were made to modify the test protocol and it is highly recommended that a second Round-Robin test be conducted to evaluate the repeatability and reproducibility of the overlay tester. Additionally, specifications for double-bladed saws were developed and three saws were purchased and delivered to Districts labs. The samples cut with these saws meet the required operational tolerances. However, it was recommended that calibration may be required on mixtures made with extremely hard rock, such as river gravels. The results obtained with both the new overlay testers and double bladed saws are presented in this report. The specifications for each device are given in the Appendices.

  • Supplemental Notes:
    • Project Title: Pilot Implementation of the Overlay Tester. Report Date: December 2007; Published: February 2008.
  • Corporate Authors:

    Texas Transportation Institute

    Texas A&M University System, 3135 TAMU
    College Station, TX  United States  77843-3135

    Texas Department of Transportation

    Research and Technology Implementation Office, P.O. Box 5080
    Austin, TX  United States  78763-5080

    Federal Highway Administration

    1200 New Jersey Avenue, SE
    Washington, DC  United States  20590
  • Authors:
    • Hu, Xiaodi
    • Zhou, Fujie
    • Scullion, Tom
  • Publication Date: 2008-2


  • English

Media Info

  • Media Type: Print
  • Edition: Technical Report
  • Features: Appendices; Figures; Photos; References; Tables;
  • Pagination: 34p

Subject/Index Terms

Filing Info

  • Accession Number: 01090204
  • Record Type: Publication
  • Report/Paper Numbers: FHWA/TX-08/5-4467-01-1, Report 5-4467-01-1
  • Contract Numbers: Project 5-4467-01
  • Created Date: Mar 17 2008 3:41PM