Document Type


Publication Date


Report Number


Granting or Sponsoring Agency

Transportation Research Board

Research Focus Area

Transportation Engineering


Several types of pavement surface distress can be attributed to delamination between hot-mix asphalt (HMA) layers. Longitudinal cracking in the wheel path and tearing in the surface are two common types of visual distress that are caused by delamination between layers. HMA delamination is primarily due to layer debonding or stripping. Debonding occurs when there is improper tack between paved HMA layers or between an HMA overlay and concrete pavement. Stripping develops when the aggregates and asphalt binder are incompatible, adhesion is lost, and water separates the asphalt binder from the aggregate. These conditions that cause pavement distress cannot be detected by visual inspection of the pavement, particularly in the early stages of the problem. The distress—cracking or tearing—are the first indicators that delamination may be occurring within the pavement layers. Agencies that maintain a roadway network need a test method to detect the location and severity of delamination before the pavement deficiency causes visual pavement distress. The test method should be applicable to network-level pavement condition assessment, projectlevel design investigation to select the correct rehabilitation strategy, and construction quality assurance. Coring is often used to measure the depth, type, and severity of delamination after the visual distress appears. This test method is destructive and is not suitable for effective evaluation of long lengths of pavement. Nondestructive testing (NDT) methods are needed to identify the presence, location (depth and area), and severity of delamination in a rapid, effective manner. The objectives of this second Strategic Highway Research Program (SHRP 2) study were to determine which NDT technologies could detect delamination and further to develop the most promising methods to accomplish construction, project design, and network-level evaluations. NDT technology for construction quality assurance should have the ability to detect debonding after placement of an HMA lift. NDT technology for project-level investigation should have the ability to provide a detailed identification of the location and severity of delamination. NDT technology for network-level assessment should have the ability to detect the presence of delamination with the test equipment operating full-lane width at safe vehicle speed.


This report is part of Second Highway Research Program 2 Report S2-R06D-RR-1 , Nondestructive Testing to Identify Delaminations between HMA Layers, Vol. 1, 2013.

Copyright Owner

National Academy of Sciences



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