15 March 2001
increase in the moisture content in the base and subbase. As thermal cycling occurs and the
joint or crack expands and contracts, incompressible material such as rocks, chunks of concrete,
sand, or ice in the crack may cause stress to build in the slab. Such stress can result in more
spalling or cracking and further damage to the slab, thereby increasing the potential for FOD.
4.4. Airfield Inspections. For airfields, inspections of the pavement surfaces receiving traffic
should be conducted at least monthly to locate spalls or cracks that may cause FOD. Otherwise,
routine field evaluations must be conducted at least biannually, once during the summer and
once during the winter. Seasonal checks allow for evaluation of the material during the two
extremes of stress on the pavement. Cracks and spalls should be located and inspected. If
concrete has begun to break away from the crack or spalled area, the damaged area must be
4.5. Cracks. Cracks less than 3/16 inch (5 millimeters) wide with no spalling do not require
sealing. Cracks 3/16 inch (5 millimeters) and larger and less than 2 inches (50 millimeters) must
be sealed. Cracks larger than 2 inches (50 millimeters) require full-depth patching. Use of a
backer rod is recommended for all crack repair. If spalling is present adjacent to a crack, the
damaged area must be repaired by treating the crack the same as an expansion joint. The
sealed crack protects the spall repaired area from damage that might result from movement of
the slab along the crack faces.
4.6. Moderate-Severity Spalling. An example of moderate-severity spalling is shown in Figure
4.1. Spalls are present from the corner of the slab and along the face of the expansion joint.
Missing chunks of concrete are visible with the potential for more pieces to become dislodged
and cause FOD. All spalled areas with loose concrete should be repaired to reduce FOD