What is Asphalt Patching?

An asphalt patch is an area of pavement where the original material was removed and replaced with a filler material (FAA AC 150/5380-6C, section 3.2.1).

What a patch is

A pothole is a hole where a part of the pavement has broken away. On an airfield it usually starts as fatigue cracking, and freeze-thaw cycles can make it worse. The FAA notes that potholes are not a common distress on airfields. A patch fills such a hole or replaces a damaged area, such as a utility cut.

How a patch is made

The FAA describes the repair of flexible pavement in its maintenance circular, and this circular is guidance, not a requirement. The steps for a full depth repair are:

1. Saw cut or mill out the area to the full depth of the asphalt. Extend the cut at least 12 inches (30 cm) beyond the damaged area.
2. Repair and re-compact the base as necessary.
3. Apply a tack coat to the bottom and sides of the cut.
4. Fill with hot-mix asphalt (HMA) equal to or better than the existing pavement, for example FAA items P-401 or P-403.
5. Check with a straight-edge that the patch is flush with the pavement next to it.
6. Keep traffic off until the HMA has cured, then clean the work area before aircraft use it.

The FAA says that partial depth repair can be an option where the pavement is thicker than 5 inches (13 cm). Full depth repair is typically needed where it is thinner. Pothole patches need warm, dry weather for best results.

Patches and FOD

A patch usually deteriorates faster than the original pavement. A deteriorated patch affects ride quality and can release loose material. That material is a FOD hazard. In the EU, the aerodrome operator must run a FOD control programme (ADR.OPS.B.016). The FAA adds that repair work can leave FOD near the repair site, so repairs need quality control and clean-up.

Patches in a PCI survey

In the PCI method for asphalt-surfaced airfields, a patch is a distress type. It counts as a defect however well it performs. The severity is low, medium or high, as the FAQ below explains. The surveyor measures the area of each severity and records it separately. Cracks inside a patch are not recorded as separate distresses. They are considered in the severity of the patch.

In the US, federally obligated airports inspect airfield pavement in detail at least once a year. A PCI survey to ASTM D5340 may extend that interval to three years (FAA AC 150/5380-7B).