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the source of maintenance headaches so they are used only when concrete movement has to be
isolated. The old practice of automatically placing expansion joints at prescribed intervals down a
pavement feature is unnecessary and has been discontinued since the 1950s. Doweled construction
joints and saw-cut contraction joints without dowels will be the default joints used for military airfield
pavement construction. Other joints will be used for special circumstances if needed or with the specific
approval of the AF MAJCOM pavements engineer, TSMCX, or NAVFAC as appropriate. These other
special application joints include:
a. Thickened-edge expansion or doweled expansion joints where isolation from concrete movement
b. Thickened-edge construction joint where load transfer cannot be provided by dowels and aircraft
traffic will cross or be adjacent to the joint.
c. Doweled contraction joint where load transfer from aggregate interlock might be lost due to slab
movement (e.g., last three contraction joints on a runway are commonly doweled because of possible
joint opening from accumulated slab movements or on long reinforced slabs where environmental
changes may result in excessive joint opening).
d. Butt longitudinal construction joints but this requires special design for no load transfer for Army
and Air Force airfield pavements.
e. Tied joints (Navy only) where relative movement and separation between slabs must be
restricted. Such situations are rare on airfield pavements.
f. Doweled construction joints will normally be used at the intersection of new and old concrete, or
alternatively the new concrete may have a thickened edge. Note that this latter situation will leave the
old concrete slab without load transfer and its premature failure should be anticipated and planned for.
Special junctures that require undercutting and placing concrete below the old slab require approval
from the AF MAJCOM pavements engineer, TSMCX, or NAVFAC as appropriate before use.
10. JOINTS FOR ARMY AND AIR FORCE PAVEMENTS.
a. Contraction Joints.
(1) General. Weakened-plane contraction joints are provided to control cracking in the concrete
and to limit curling or warping stresses resulting from drying shrinkage and contraction and from
temperature and moisture gradients in the pavement. Shrinkage and contraction of the concrete causes
slight cracking and separation of the pavement at the weakened planes, which will provide some relief
from tensile forces resulting from foundation restraint and compressive forces cause by subsequent
expansion. Contraction joints will be required transversely and may be required longitudinally depending
upon pavement thickness and spacing of construction joints. A typical contraction joint is shown in
Figure 12-30. Instructions regarding the use of saw cuts to form the weakened plane are contained in
TM 5-822-7/AFM 88-6, Chapter 8.
(2) Width and Depth of Weakened-Plane Groove. The width of the weakened-plane groove will
be a +3 millimeters (+1/8 inch) or greater. The depth of the weakened plane groove must be great
enough to cause the concrete to crack under the tensile stresses resulting from the shrinkage and
contraction of the concrete as it cures. Experience, supported by analyses, indicates that this depth
should be at least one-fourth of the slab thickness for pavements less than 300 millimeters (12 inches),