What are some Best Practices that should be considered when applying a Tack Coat?
In general, the surface that the tack coat is to be applied to should be clean and dry. Dirt and moisture will not allow the tack to stick to the base layer eliminating its value. The surface should be swept and visually moisture free. All surfaces should be tack coated for best results, this includes the sides of curbs, adjacent asphalt, etc. A milled surface will provide the opportunity to improve the road profile and will improve the bonding characteristics of the Tack Coat, but there may be an extra effort necessary to clean the surface.
Important items for an Inspector to check should be the spray truck setup, the desired application and residual rates, visual inspection of the application and verify the application rate. The application rate will vary depending on the surface it is to be applied to. Application of the Tack Coat should not extend too far beyond the paver.
Items to check on the spray truck include:
- Spray bar height (~12 inches)
- Nozzle orientation (15–30 degrees to allow for triple coverage in case of nozzle clogging)
- Truck application rate gauge
- Application Temperature
Samples of the asphalt should be collected for future testing, if necessary