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One of WSDOT maintenance crews’ priorities is repair. Fixing cracks, buckles, or potholes while they’re small can prevent costly future repairs. Patching cannot be done in cold or wet weather; it is a summer maintenance task.

There are five steps in the patching process:

  • Apply a layer of liquid asphalt – also called "tacking." The tack layer allows the hot mix of gravel and oil (tar) to bond to the existing pavement. It takes the tack five to 15 minutes to cure (depending upon temperature), before the hot mix is applied.
  • Apply the hot mix, a "belly dump" mechanism on a semi-truck trailer rig is used for application directly onto the tack layer. This could involve several rigs, depending upon the size of the patch.
  • Grader operators work the hot asphalt mix into the areas where the pavement failed, then level and smooth the material to avoid lumps, bumps, or an edge where the patch and existing pavement meet.
  • Before the asphalt is set, steel-wheeled rollers compact the paving material. This provides a harder, smoother road surface.
  • The final step is traffic markings for safe driving over the newly paved patch.