What is a Seal Coat Condition Inspection?
A seal coat inspection is a survey that records the distresses in an asphalt surface treatment, such as a seal coat or slurry seal.
On airfield pavements the FAA treats seal coating as preventive maintenance. A seal coat is an emulsified asphalt surface treatment. The FAA specification Item P-608 uses the terms seal coat and asphalt sealer for the same thing. It requires aggregate in the seal coat on runways and high-speed taxiways.
Where each treatment is allowed
The FAA limits each surface treatment to certain pavements.
- Seal coat (P-608): taxiways and runways with aggregate, on pavements in fair or better condition and on low to moderate weathered surfaces.
- Chip seal (P-609): not recommended on airfield pavements. It may leave loose aggregate on the surface.
- Slurry seal (P-626): all pavements at general aviation airports for airplanes of 30,000 lb or less. At airports for airplanes of 60,000 lb or less, all pavements except runways.
- Rejuvenator (P-632), commonly called a fog seal: not for runways or acute-angled exit taxiways.
What the inspector records
The inspection records the distresses that the PAVER distress manual defines, with their severity and area. The ones that apply to a surface treatment are:
- Weathering: the wearing away of the asphalt binder and fine aggregate from the surface.
- Raveling: the dislodging of coarse aggregate particles. For a slurry seal or coal tar, the severity depends on the scaled area. It is low below 1 percent, medium from 1 to 10 percent and high above 10 percent.
- Bleeding: a shiny, sticky film of bituminous material on the surface.
- Block cracking: interconnected cracks that usually show hardened asphalt.
- Slippage cracking: crescent-shaped cracks that occur when the surface mix is weak or bonds poorly to the layer below.
The rated distresses give the Pavement Condition Index (PCI), a number from 0 for a failed pavement to 100 for a new one.
How often
Federally obligated airports inspect airfield pavements in detail at least once a year. A PCI survey to ASTM D5340 may extend this to three years. The airport also sets a schedule for routine inspections and does daily drive-by inspections.
After a crew places a seal coat on a runway or high-speed taxiway, P-608 requires wet friction tests at 40 mph and 60 mph.
Drone survey
The FAA Airport Technology R&D Branch tested small drones for pavement inspection at five airports from 2020 to 2022. Its report lists the pavement distresses that drone imagery can identify.
TarmacView surveys airfield pavement by drone to an ASTM D5340 distress inventory and a PCI.
Frequently Asked Questions
- Can a seal coat be used on a runway?
- Yes. The FAA seal coat specification, Item P-608, covers runways and taxiways with a suitable aggregate to keep the surface friction adequate. The spray seal coat (P-623) and the rejuvenator (P-632) are not for runways. A chip seal (P-609) is not recommended on airfield pavements.
- How often must a seal coat be inspected?
- The FAA sets the interval for the airfield pavement, not for the seal coat alone. Federally obligated airports inspect all airfield pavements in detail at least once a year. If the airport does a PCI survey to ASTM D5340, the detailed inspection may be extended to every three years. Each airport also sets a schedule for routine inspections.
- What counts as high raveling on a slurry seal?
- In the PAVER manual, raveling on a slurry seal or coal tar is high severity when the scaled area is more than 10 percent. It is low severity below 1 percent and medium from 1 to 10 percent. Raveling on a normal asphalt mix is rated by missing aggregate particles instead.
References
- faa-ac-150-5370-10h
- AC 150/5370-10H, Standard Specifications for Construction of Airports FAA
- faa-ac-150-5380-6c
- AC 150/5380-6C, Guidelines and Procedures for Maintenance of Airport Pavements FAA
- faa-ac-150-5380-7b
- AC 150/5380-7B, Airport Pavement Management Program (PMP) FAA
- paver-asphalt-distress-manual
- PAVER Distress Identification Manual for Asphalt Surfaced Airfields US Army Corps of Engineers ERDC-CERL
- faa-tc-23-39
- Assessment of Small Unmanned Aircraft Systems for Pavement Inspections (DOT/FAA/TC-23/39) FAA Airport Technology R&D Branch
This is a reference entry. TarmacView provides drone inspection services and doesn't sell the equipment or materials described in this glossary.
