What is a Blowup in Concrete Pavement?
A blowup is an upward buckling or shattering of concrete slab edges at a joint or crack when the joint cannot absorb thermal expansion.
How a blowup forms
Concrete slabs expand when they heat up. A joint leaves space for this movement. If the joint is too narrow, the slabs push on each other, and the edges buckle upward or shatter. This happens in hot weather, usually at a transverse crack or joint (FAA PAVER manual).
Two things close a joint. Incompressible material, such as soil or rock, enters the joint space. Alkali-silica reaction (ASR) can also expand the concrete and close the joint gradually (FAA AC 150/5380-6C). A damaged joint seal lets this material in.
Where blowups occur
- At a transverse crack or joint.
- At utility cuts and drainage inlets.
- In thin pavement sections. AC 150/5380-6C says blowups normally occur only there.
- Under an asphalt overlay. The dark surface absorbs more heat (AC 150/5380-6C). AC 150/5320-6G says thin asphalt overlays of rigid pavement may cause or worsen blowups.
AC 150/5380-6C calls blowups “not common”.
Why a blowup matters on an airfield
The PAVER manual says a blowup is almost always repaired immediately, because it can damage aircraft. ICAO Annex 14, 10.2.1, requires regular inspection of movement area pavements to avoid and eliminate foreign object debris (FOD). EASA guidance (AMC1 ADR.OPS.B.015) says the operator should make extra inspections during excessive heat to check for blow-ups and debris.
How a blowup is rated
The PAVER manual lists the blowup as distress 61 for concrete airfields. It sets three severity levels:
- Low: the pavement is still usable and has a little roughness.
- Medium: the pavement is still usable and has significant roughness.
- High: the pavement is not usable.
A pavement counts as operational only after all foreign material from the blowup is removed. At a crack the blowup counts as one slab. At a joint it counts as two slabs.
Repair
The FAA maintenance guide gives one repair for a slab blowup: replace the slab in the blowup area, then clean and reseal the joints. The listed cause is incompressible material in the joints, which prevents the slab from expanding (AC 150/5380-6C, Table 6-2).
Frequently Asked Questions
- What is a blowup in concrete pavement?
- A blowup is a localized upward movement (buckling) or shattering of concrete slab edges near a joint or crack. It occurs in hot weather, usually at a transverse crack or joint that is too narrow to let the slabs expand. Infiltration of incompressible material into the joint space is the usual cause.
- What causes a blowup?
- A joint that is too narrow for the thermal expansion of the slabs causes a blowup. Incompressible material in the joint space, such as soil or rock, closes the gap. Alkali-silica reaction (ASR) can also close the joint, because the expansion of the concrete narrows it over time.
- How is a blowup repaired?
- The FAA guide for rigid pavement lists one repair: replace the slab in the blowup area, then clean and reseal the joints. The PAVER manual says a blowup is almost always repaired immediately, because it can damage aircraft.
- Does a blowup need an extra inspection?
- In hot weather, yes. EASA guidance says the aerodrome operator should make extra inspections of paved areas during excessive heat. The inspection checks for pavement blow-ups and debris.
References
- faa-paver-concrete
- PAVER Distress Identification Manual, Concrete Surfaced Airfields FAA
- faa-ac-150-5380-6c
- AC 150/5380-6C, Guidelines and Procedures for Maintenance of Airport Pavements FAA
- faa-ac-150-5320-6g
- AC 150/5320-6G, Airport Pavement Design and Evaluation FAA
- easa-ear-aerodromes
- Easy Access Rules for Aerodromes (Regulation (EU) No 139/2014), CS-ADR-DSN Issue 7 EASA
This is a reference entry. TarmacView provides drone inspection services and doesn't sell the equipment or materials described in this glossary.
