Figure 3. Aggregate surfacing design curve for Class II airfields.

Aggregate Surfaced Roads and Airfields Areas
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TM 5-822-12

Figure 3. Aggregate surfacing design curve for Class II airfields.

b. Required layers in pavement section. When

characteristics and helps to provide a relatively smooth

riding surface.

frost is a consideration, it is recommended that the

pavement section consist of a series of layers that will

d. Base course. The coarse-graded base course is

ensure the stability of the system, particularly during

thaw periods. The layered system in the aggregate fill

important in providing drainage of the granular fill. It is

may consist of a wearing surface of fine crushed stone,

also important that this material be nonfrostsusceptible

a coarse-graded base course, and/or a well-graded

so that it retains its strength during spring thaw periods.

subbase of sand or gravelly sand. To ensure the

stability of the wearing surface, the width of the base

e. Subbase. The well-graded sand subbase is

course and subbase should exceed the final desired

used for additional bearing capacity over the frost-

surface width by a minimum of 1 foot on each side.

susceptible subgrade and as a filter layer between the

coarse-graded base course and the subgrade to prevent

c. Wearing surface. The wearing surface contains

the migration of the subgrade into the voids in the

fines to provide stability in the aggregate surface. The

coarser material during periods of reduced subgrade

presence of fines helps the layer's compaction

strength. The material must therefore meet standard

filter criteria.