30 June 2001
Design Gear Load, kg (lb)
The design tire pressure for the F-14 is 1.65 MPa (240 psi).
(4) Slab thickness and joints. The k value of 54 kPa/mm (200 pci) as determined above and a
design flexural strength of 4.48 MPa (650 psi) are used to determine the required slab thickness.
Results of the mixed traffic analysis for the channelized traffic areas are summarized in Table 12-5.
Results for the unchannelized traffic areas are summarized in Table 12-6. This shows that a
345-millimeter (13.6-inch) concrete slab is required in areas of channelized traffic to serve the projected
aircraft over a design life of 20 years. This is rounded up to a recommended thickness of 350 millimeters
(14.0 inches). A 330-millimeter (13.0-inch) concrete slab is required in areas with unchannelized traffic.
8. JOINT USES. Joints are provided to permit contraction and expansion of the concrete resulting from
temperature and moisture changes, to relieve warping and curling stresses due to temperature and
moisture differentials, to prevent unsightly irregular breaking of the pavement, and to act as a
construction expedient to separate sections or strips of concrete placed at different times. The three
general types of joints are contraction, construction, and expansion. A typical jointing layout of the three
types is illustrated in Figure 12-29.
9. SELECTION OF JOINT TYPES. Joints are either construction or contraction joints. Construction
joints are used because there is a physical limit on the concrete placement such as the beginning or end
of a placement lane (transverse construction joint) or at the edges of the placement lane (longitudinal
construction joint). Concrete is a dynamic material that changes volume throughout its life as chemical
reactions occur and as temperature and moisture fluctuations occur. Either joints must be provided to
accommodate these natural volume changes in concrete or the concrete will crack. Such joints are
contraction joints and are formed by sawing partial depth into the concrete at early ages before cracking
can occur. This sawing must be done as soon as the concrete has hardened sufficiently to allow saw
cutting without raveling or damage to the concrete. The exact timing of the saw cutting depends on the
characteristics of the concrete mixture and the environmental conditions. This cutting occurs on the
same day as placing except under very unusual circumstances. Waiting overnight to cut these joints
generally will result in uncontrolled cracking. Contraction joints made by inserts forced into the plastic
concrete or by manually grooving the plastic concrete surface are unacceptable for military airfields. The
most common contraction joints are the regularly spaced transverse joints (transverse contraction joints)
placed down the length of the concrete placement lane. The maximum spacing between joints is a
function of the slab thickness and allowable limits are provided in paragraph 10. When the concrete
placement lane width exceeds these allowable limits between joints, a longitudinal contraction joint will
be placed to bring the joint spacing within the maximum limits. The resulting slabs should be square. If
the ratio of length to width falls outside of the range of 0.75 to 1.25 or if the geometry of the pavement
dictates an irregular shaped slab (e.g., filet slabs), the slabs will have to be reinforced as required in
Chapters 1 and 13. Expansion joints are special construction joints that are used to isolate structures
from the concrete pavement movement (e.g., isolate hangar from an apron) or to separate two
intersecting pavements (e.g., a taxiway intersecting a runway at right angles). Expansion joints often are