Evaluation of Tack Coat Bond Strength Tests

Poor bonding between asphalt pavement overlays and the substrate pavement layer can greatly influence the long term performance of hot mix asphalt (HMA) in the form of premature cracking and fatigue. The primary method to achieve bonding between layers is by using an asphalt emulsion tack coat. Additionally, field staff is charged with determining whether an existing pavement, especially a milled surface, is clean enough prior to tack coat placement, to ensure an adequate bond. Because CDOT is prescriptive in its tack coat application specifications, responsibility for any pavement failures related to poor bonding lies with CDOT. However, if a performance related test to measure tack coat bond strength could be specified, failures related to poor bonding should be reduced. This study evaluated four bond strength tests for SMA and HMA overlays on HMA and Portland cement concrete pavements. Results of this study indicate that bond strength of HMA overlays can be measured using pavement cores, that a significant difference in test precision was observed when CRS-2P was used a tack coat and that one of the test pavements demonstrated significantly poorer than recommended bond strength for the tack coat utilized. Recommendations are provided for developing a performance related specification based on future performance observed on the four pavements. Implementation of this research can be done as follows: 1) specify a minimum tack coat application rate of 0.05 gal/sq-yd of 50:50 diluted CSS-1h or CRS-2P for construction of dense graded HMA over other dense graded HMA.


  • English

Media Info

  • Media Type: Digital/other
  • Edition: Final Report
  • Features: Figures; Photos; References; Tables;
  • Pagination: 36p

Subject/Index Terms

Filing Info

  • Accession Number: 01670886
  • Record Type: Publication
  • Report/Paper Numbers: CDOT-2018-14, CDOT-DTD-R-2018-14
  • Created Date: May 22 2018 11:36AM