What is a Popout in Concrete Pavement?

A popout is a small piece of pavement that breaks loose from the surface of a concrete slab and leaves a hole. The FAA and the PAVER distress manual give the same definition.

Cause and size

Freeze-thaw action in combination with expansive aggregates causes most popouts. Alkali-silica reaction (ASR) can also cause them, and aggregate popouts are one sign of ASR in a slab. A single piece of large aggregate can break loose. Clay balls in the mix can do the same.

A popout is usually 25 to 100 mm (1 to 4 inches) in diameter. It is usually 13 to 50 mm (1/2 to 2 inches) deep.

Popout and scaling

A popout is a local hole. Scaling is different. Scaling is the disintegration and loss of the wearing surface. Poor curing or finishing and freeze-thaw cycles weaken the surface and can lead to scaling.

Popouts on an airfield

Pavement distress can produce loose material. Loose material can strike propellers or enter jet engines. The FAA calls this material FOD (foreign object debris), and it says every pavement inspection should address FOD.

The FAA repair table for rigid pavement lists “remove FOD” for popouts. It gives the material as the probable cause.

Aggregate choice also affects popouts. The FAA construction specification for concrete pavement (P-501) limits chert below 2.40 specific gravity in coarse aggregate. A note in the specification covers freeze-thaw areas with chert popouts. It tells designers to check that compliant aggregate exists before they lower the chert limit.

Popouts in a condition survey

ASTM D5340 sets the procedure for the PCI (Pavement Condition Index). In the PAVER method, popouts have no severity levels. A slab counts only if the average density exceeds about three popouts per square yard (square meter). When the count is in doubt, the inspector checks three random areas of 1 square yard.