Development of a Tack Coat Quality Control Program for Mitigating Delamination in Asphalt Pavement Layers

The importance of proper bonding at the asphalt concrete (AC) layer interface cannot be overemphasized when discussing the performance of AC pavements. A strong bond between the layers is critical to dissipate shear stress throughout the entire pavement structure. In contrast, insufficient bonding may cause slippage and debonding between the asphalt layers. To mitigate the debonding distress, the type, quantity, and quality of the tack coat materials that are applied between asphalt layers need to be addressed properly. Research at North Carolina State University (NCSU) under the HWY-2014-03 project has led to the development of a device known as the Tack Lifter. The Tack Lifter is used for measuring the tack coat application rate, the residual tack coat application rate, and the effective tack coat rate (which indicates the tack coat that is not absorbed by the pavement surface). The Tack Lifter represents an important step forward in the development of a tack coat quality control (QC) program; however, it is necessary to determine the minimum required tack coat application rate in order for the Tack Lifter to be used as an effective QC device. The NCDOT HWY-2013-04 project is another important research project undertaken at NCSU that focused on mitigating the debonding distress. Work in this project determined the critical shear stress under moving loads and developed relationships between the interlayer shear strength of layered AC with unmilled surfaces and the bitumen bond strength (BBS) of tack coat materials. The analytical and experimental methodologies developed under the HWY-2013-04 project should be extended to milled pavement surfaces, which are a very common type of pavement surface where asphalt overlay is applied. The primary objective of the proposed research is to develop a comprehensive tack coat QC program to mitigate the debonding distress in asphalt pavements using the Tack Lifter and the methodologies developed under the HWY-2013-04 project. This QC program will include minimum application rates possibly for different tack coat materials, the minimum required BBS for tack coat materials, a laboratory test procedure to determine the BBS of tack coats, and visual inspection guidelines for the qualitative evaluation of existing pavement surfaces and tack coat materials. The implementation of an effective tack coat QC program will lead to improved monitoring of pavement construction and to the verification of pavement layer bond strength in two ways. First, combining a laboratory test to verify the quality of the tack coat material and a field test to check the proper residual tack coat application rate will ensure adequate bond strength between the pavement layers. Second, ensuring adequate bond strength will reduce the occurrence of premature distresses, thereby leading to savings in pavement maintenance and rehabilitation costs in the long term.


  • English


  • Status: Active
  • Funding: $311127
  • Contract Numbers:


  • Sponsor Organizations:

    North Carolina Department of Transportation

    Research and Development
    1549 Mail Service Center
    Raleigh, NC  United States  27699-1549
  • Project Managers:

    Kadibhai, Mustansir

  • Performing Organizations:

    North Carolina State University

    Department of Civil Engineering, Campus Box 7908
    Raleigh, NC  United States  27695-7908
  • Principal Investigators:

    Kim, Y

  • Start Date: 20170801
  • Expected Completion Date: 20200630
  • Actual Completion Date: 20190731
  • Source Data: RiP Project 41773

Subject/Index Terms

Filing Info

  • Accession Number: 01641214
  • Record Type: Research project
  • Source Agency: North Carolina Department of Transportation
  • Contract Numbers: 2018-13
  • Files: RIP, STATEDOT
  • Created Date: Jul 19 2017 1:01AM