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De-Bonding of Hot Mix Asphalt Pavements in Washington State: An Initial Investigation

Description: Recent evidence in Washington State indicates that de-bonding of HMA (Hot Mix Asphalt) surface layers may become a significant problem. “De-bonding” describes a condition where adjacent layers of HMA lose adhesion to one another and can become separated. Typically, design and construction practice is to build in a certain amount of bonding. However, the appropriate amount, testing and techniques are still under debate. For WSDOT pavements, which are generally thick and long-lasting, this de-bonding is thought to be more prevalent between the surface layer (usually applied as a preservation overlay) and underlying layers. This de-bonding may contribute to early failure of the HMA pavement surface layer, which can increase pavement preservation costs. This study gathers initial evidence on de-bonding in Washington State and attempts to define the problem scope and potential performance impacts. Specifically, it attempts to (1) determine if de-bonding occurs, (2) identify possible de-bonding mechanisms, (3) define the scope of de-bonding in WSDOT pavements, (4) determine de-bonding impacts on pavement performance, and (5) identify the role of tack coats in de-bonding. 

A summary of this study with additional pictures is available on Pavement Interactive at:

  • Date Published: November, 2008
  • Publication Number: WA-RD 712.1
  • Last Modified: July 22, 2009
  • Authors: Stephen T. Muench, Tim Moomaw.
  • Originator: Transportation Northwest Regional Center X (TransNow)
  • # of Pages: 53 p., 6.05 MB (PDF)
  • Subject: Hot mix paving mixtures, Bonding, Adhesion, Surface course (Pavements), Overlays (Pavements), Pavement layers, Evaluation and assessment, Asphalt pavements, Pavement performance, Pavement maintenance.
  • Keywords: Hot mix asphalt, de-bonding, tack coat, bonding, layer, cracking, construction, asphalt, emulsion.
  • Related Publications:

This abstract was last modified January 22, 2013