TM 5-822-5/AFM 88-7, Chap. 1
for all transverse construction joints in plain
nonextruding type. The type and thickness of filler
concrete pavements.
material and the manner of its installation will
(2) Thickened-edge joint. Thickened-edge-
depend upon the particular case. Usually, a
type joints may be used instead of other types of
preformed material of -inch thickness will be
joints employing load transfer devices. When the
adequate; however, in some instances, a greater
thickened-edge joint is constructed, the thickness of
thickness of filler material may be required. Filler
the concrete at the edge is increased to 125 percent
material for slip joints will be either a heavy coating
of the design thickness. The thickness is then re-
of bituminous material not less than 1/16 inch in
duced by tapering from the free-edge thickness to
thickness when joints match or a normal
the design thickness at a distance of 3 feet from the
nonextruding-type material not less than inch in
longitudinal edge. The thickened-edge joint is
thickness when joints do not match. Where large
considered adequate for the load-induced concrete
expansions may have a detrimental effect on
stresses. However, the inclusion of a key in the
adjoining structures, such as at the juncture of rigid
thickened-edge joint (fig 15-4d) provides some
and flexible pavements, expansion joints in
degree of load transfer in the joint and helps to
successive transverse joints back from the juncture
maintain slab alignment; although not required, it is
should be considered. The depth, length, and
recommended for pavement constructed on low-to
position of each expansion joint will be sufficient to
medium-strength foundations. The thickened-edge
form a complete and uniform separation between
joint may be used at free edges of paved areas to
the pavements or between the pavement and the
accommodate future expansion of the facility or
structure concerned.
(1) Between pavement and structures. Expan-
where wheel loadings may track the edge of the
pavement. The use of this type joint is contingent
sion joints will be installed to surround, or to sepa-
upon adequate base-course drainage meeting
rate from the pavement, any structures that project
requirements of TM 5-820-2/AFM 88-5, Chap 2.
through, into, or against the pavements, such as at
(3) Keyed joint. The keyed joint is the most
the approaches to buildings or around drainage
economical method, from a construction standpoint,
inlets. The thickened-edge-type expansion joint will
for providing load transfer in the joint. It has been
normally be best suited for these places (see fig 15-
demonstrated that the key or keyway can be satis-
5).
(2) Within pavements and at pavement inter-
factorily constructed using either formed or slim
sections. Expansion joints within pavements are
formed methods. The required dimensions of the
joint can best be maintained by forming or slim
difficult to construct and maintain and often con-
forming the keyway rather than the key. The di-
tribute to pavement failures. Their use will be kept
mensions and location of the key are critical to its
to the absolute minimum necessary to pre- vent
performance. Deviations exceeding the stated tol-
excessive stresses in the pavement from expansion
erances can result in failure in the joint. Keyed joints
of the concrete or to avoid distortion of a pavement
should not be used in rigid pavements that are less
through the expansion of an adjoining pavement.
than 9 inches in thickness. Tie bars in the keyed
The determination of the need for and spacing of
joint will limit opening of the joint and provide
expansion joints will be based upon pavement
some shear transfer that will improve the
thickness, thermal properties of the concrete,
performance of the keyed joints. However, tieing all
prevailing temperatures in the area, temperatures
joints in pavement widths of more than 75 feet can
during the construction period, and the experience
result in excessive stresses and cracking in the
with concrete pavements in the area. Unless needed
concrete during contraction.
to protect abutting structures, expansion joints will
c. Expansion joints. Expansion joints will be
be omitted in all pavements 10 inches or more in
used at all intersections of pavements with struc-
thickness and also in pavements less than 10 inches
tures or with other concrete pavements where
in thickness when the concrete is placed during
paving lanes are perpendicular to each other, and
warm weather since the initial volume of the
they may be required within the pavement features.
concrete on hardening will be at or near the
A special expansion joint, the slip joint, is required
maximum. However, for concrete placed during
at pavement intersections. The types of expansion
cold weather, expansion joints may be used in
joints are the thickened-edge joint, the thickened-
pavements less than 10 inches thick.
(a) Longitudinal expansion joints within
edge slip joint, and the doweled type joint (see figs
15-5 and 15-6). Filler material for the thickened-
pavements will be of the thickened-edge type (see
edge and doweled type expansion joint will be a
fig 15-5). Dowels are not recommended in longitu-
15-16
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