What is a Joint Sealant?
A joint sealant is a resilient material in the joints of a concrete pavement that keeps water and incompressible material out of the joint. The joints let the slabs move. An open or damaged joint lets soil, stones and water in.
Why the seal matters
The FAA defines joint seal damage as any condition that lets water into the joints. It also covers any condition that lets soil, rocks or other incompressible material collect there. Collected material stops the slabs from expanding. This can cause buckling, shattering or spalling. Water that gets through the joint can cause pumping or deterioration of the base. Typical damage is stripped or extruded sealant, hardened (oxidised) filler, loss of bond to the slab edges and sealant missing from the joint. The FAA lists these causes. They are wrong joint width, wrong sealant type, incorrect application, a joint not cleaned before sealing, and ageing.
Sealant types in FAA specifications
FAA Item P-605 covers joints formed in place. The engineer chooses one or more of these standards:
- ASTM D6690, hot-applied joint and crack sealant for concrete and asphalt pavements.
- ASTM D7116, hot-applied, jet-fuel-resistant sealant for concrete pavements. It is limited to concrete aprons where aircraft are fuelled. Such an apron may use either ASTM D7116 or ASTM D5893.
- ASTM D5893, cold-applied, single-component, chemically curing silicone sealant for concrete pavements.
FAA Item P-604 covers preformed compression seals. They are polychloroprene seals to ASTM D2628 with a lubricant/adhesive. Where jet fuel or heat blast resistance is required, the contract can add Corps of Engineers specification CRD C548.
How a joint is sealed
Item P-605 requires a dry joint, clean of scale, dirt, dust, curing compound and old sealant. The contractor cleans it by sandblasting, routing, sawing or waterblasting, as the engineer specifies. Compressed air then clears debris and water from the joint just before sealing. A backer rod to ASTM D5249 sets the depth of the sealant. The rod is 25 percent, plus or minus 5 percent, larger in diameter than the joint width. The contractor fills the joint from the bottom up, to a level just below the pavement surface.
The shape factor is the depth of the sealant divided by the width of the joint. The P-605 design notes give a shape factor of 1. An ASTM D5893 sealant sometimes needs a shape factor of 0.5, which means the sealant depth is half its width.
Rating the condition
Joint seal damage is a distress in the Pavement Condition Index (PCI) survey for jointed concrete pavements. The PAVER manual rates it as low, medium or high for the whole sample unit. Medium severity is a sealer in generally fair condition that needs replacement within 2 years. Signs of it include these. A visible opening of up to 3 mm (1/8 inch) at the joint edge. Pumping debris at the joint. Lifeless oxidised sealer. Obvious vegetation in the joint. High severity is a sealer in generally poor condition that needs immediate replacement.
Airfield inspection
Joint seal damage is one of the distresses that a pavement survey records. The FAA maintenance guidance repairs it by removing the old sealant, cleaning the joints and resealing.
Frequently Asked Questions
- What does a joint sealant do?
- A joint sealant keeps water and incompressible material out of a pavement joint. Incompressible material in the joint stops the slabs from expanding and can cause buckling, shattering or spalling. Water that gets through the joint can cause pumping or deterioration of the base.
- Which joint sealants does the FAA specify for airport pavements?
- The FAA names formed-in-place sealants in Item P-605 and compression seals in Item P-604. In P-605 the engineer chooses one of three. They are hot-applied ASTM D6690, jet-fuel-resistant hot-applied ASTM D7116, and cold-applied silicone ASTM D5893. P-604 covers preformed polychloroprene compression seals to ASTM D2628.
- How is joint seal damage rated?
- Joint seal damage is rated at low, medium or high severity for the whole sample unit, not slab by slab. The PAVER distress manual describes low as a sealer in generally good condition. It describes high as a sealer in generally poor condition that needs immediate replacement. High severity applies when 10 percent or more of the sealer fails the criteria or is missing.
- How often must a joint sealant be inspected?
- FAA guidance sets no inspection interval for joint sealant alone. Federally obligated airports must do a detailed inspection of their airfield pavements at least once a year for the pavement management program. A PCI survey to ASTM D5340 may extend that interval to three years.
References
- faa-ac-150-5380-6c
- AC 150/5380-6C, Guidelines and Procedures for Maintenance of Airport Pavements FAA
- faa-ac-150-5370-10h
- AC 150/5370-10H, Standard Specifications for Construction of Airports, Items P-604 and P-605 FAA
- paver-concrete-distress
- PAVER Distress Identification Manual, Concrete Surfaced Airfields US Army Corps of Engineers ERDC-CERL
- faa-ac-150-5380-7b
- AC 150/5380-7B, Airport Pavement Management Program (PMP) FAA
This is a reference entry. TarmacView provides drone inspection services and doesn't sell the equipment or materials described in this glossary.
