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Patching
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.
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