Planning the Next Generation of Seal Coat Equipment

Seal coats are a very important preventive maintenance method used throughout Texas. Through the preventive maintenance program, about 16,000 lane miles a year are routinely resurfaced with a seal coat by contracts and about 3,000 lane miles per year of seal coats are placed with State forces. Additionally, Seal coats are used in intermediate layers during construction to seal the pavement structure. This is a significant investment of over $300 million annually. For more than 40 years, there has been little change in the design and construction practices, including equipment used to place the asphalt or aggregate. With little to no changes in design and construction methods, Texas continues to see the same problems, such as rock loss, flushing and bleeding reoccurring. New technologies are being developed that could potentially reduce these types of problems. There have been recent new developments for asphalt distributors due to the performance based warranty specification being used by the New Zealand Transport Agency. The asphalt distributor improvements include the ability to use up to eight different transversely varying application rates at normal operating speed. This is extremely useful to apply the optimal shot rate when surface conditions change. In addition to this, high definition video systems and scanners can map and document existing texture conditions to define the required spray bar pattern. Therefore, this study will investigate new technologies for improvements to seal coat design and construction. A work plan will address the following goals: (1) Investigate the current state of practice in innovative agencies around the U.S. and internationally. This includes New Zealand, Australia, and South Africa, who have very similar roadway conditions to Texas. Focus on spray bar technology and other implementable practices. (2) Survey local distributor and spray bar manufacturers to determine what is currently available and what enhancements can be made. (3) Construct a prototype spray bar control system or develop detailed plans for what it would take to construct an appropriate system to accommodate Texas conditions. (4) Evaluate new approaches for documenting up-front pavement texture conditions, with the idea of using automated texture measurements to help determine shot rates. Identify optimal shot rates for the most common conditions found in Texas; for example, the different severity levels of bleeding wheel paths and limestone rock asphalt patches. (5) Develop an approach where the technologies can be merged together and implemented in future studies.


  • English


  • Status: Active
  • Contract Numbers:


  • Sponsor Organizations:

    Texas Department of Transportation

    125 E. 11th Street
    Austin, TX  United States  78701-2483
  • Project Managers:

    Adams, Joe

  • Performing Organizations:

    Texas Transportation Institute

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

    Goehl, Darlene

  • Start Date: 20170901
  • Expected Completion Date: 20180831
  • Actual Completion Date: 0

Subject/Index Terms

Filing Info

  • Accession Number: 01648628
  • Record Type: Research project
  • Source Agency: Texas Department of Transportation
  • Contract Numbers: 0-6963
  • Files: RiP, STATEDOT
  • Created Date: Oct 20 2017 12:05PM