Airport pavement is designed to withstand the
stresses imparted to the pavement by aircraft. Depending on the use and local
ground conditions, materials are chosen to construct the runway. For a major
airport, where the ground conditions permit, the most satisfactory type of
pavement for long-term minimum maintenance is concrete. Although certain
airports have used reinforcement in concrete pavements, this is generally found
to be unnecessary, with the exception of expansion joints across the runway
where a dowel assembly, which permits relative movement of the concrete slabs,
is placed in the concrete.
Where it can be anticipated that major
settlements of the runway will occur over the years because of unstable ground
conditions, it is preferable to install asphaltic concrete surface, as it is
easier to patch on a periodic basis. For fields with very low traffic of light
planes, it is possible to use a sod surface. Some runways also make use of salt
flat runways.
For heavy-duty commercial aircraft, the pavement
thickness, no matter what the top surface, varies from 10 in (250 mm)
to 4 ft (1 m), including subgrade. These is determined by the
subgrade condition (determined by borings). The specifications are established
from the relative bearing capacity of the subgrade.
Post-tensioning concrete has been developed for the runway surface. This permits the use of thinner pavements and should result in longer concrete pavement life. Because of the susceptibility of thinner pavements to frost heave, this process is generally applicable only where there is no appreciable frost action.
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