Thin asphalt overlays: surface evaluation and preparation
When evaluating pavement surfaces to determine whether or not they’re appropriate for thin asphalt overlays, it’s important to determine what distresses are currently in the pavement. Potential distresses include:
- Raveling – a loss of fine aggregate in the pavement surface resulting in a coarse and weathered appearance.
- Longitudinal cracking
- Not in the wheelpath: Cracking resulting from the deterioration of a longitudinal joint or as a result of a crack reflecting through the surface from a lower layer.
- In the wheelpath: Cracking resulting from the application of traffic loads causing excess tensile strains.
- Transverse cracking – Cracking occurring at a 90 degree angle to the direction of traffic, due to either the expansion and contraction of the pavement surface or as a result from cracks in lower layers reflecting through the surface.
- Alligator or Fatigue Cracking - Interconnected cracks occurring in the wheelpath resulting from the application of excessive traffic loads.
- Rutting or Shoving – A distortion of the pavement surface in the wheelpaths resulting from a lack of shear strength in one or more pavement layer
Once the types of pavement distress have been evaluated, the following table can be used to determine the approach that is necessary in order to prepare the pavement for thin overlay:
- (Source: NAPA publication, Thin Overlays for Pavement Preservation)
Other resources:
- The National Asphalt Paving Association offers a very comprehensive downloadable document about Thin Overlays that can be found at their page on Thin Overlays.
- Additionally, their webinar on Thin Overlays comes highly recommended.
- Pavement Interactive’s resources for specific pavement distress types have been linked to above and in addition, the page on Non-Structural Overlays is helpful.
Tags: Pavement distress types, Surface prepration for thin overlays, Thin asphalt overlays