TM 5-822-7/AFM 88-6, Chap. 8
avoid uncontrolled cracking. Sawing too early,
concrete being placed because the load transfer
however, will be guarded against to prevent
between the slabs depends on the interlock of aggre-
excessive washing and undercutting of concrete in
gate below the formed portion of the joint and
material that is not deep enough will not produce
the joint. The proper time for sawing the joints will
be determined for prevailing conditions on the job
cracking at the proper location. Insert material must
during each concrete placement. Since conditions
be placed flush with the surface to not more than 1/8
may change from day to day, it is essential that the
inch below the surface. The surface of the pavement
saw operator be experienced in sawing pavement
will be finished with a vibratory float; hand floating
joints.
will not be permitted. When finishing concrete after
installation of the insert, an excessive amount of fine
(c.) Sawing sequence. Transverse joints will be
sawed consecutively in the same sequence as the
material must not be worked to the surface and adja-
concrete is placed in the lane. Sawing of alternate
cent to the insert. Excessive fines will cause scaling
of the surface and spalling of the joint.
joints in the pavement is undesirable because
concrete tends to tear ahead of the saw cut when
(4.) Sawing of transverse contraction joints.
intermediate joints are sawed. This procedure also
(a.) Method. Transverse and longitudinal
contraction joints shall be constructed to conform
reduces the uniformity of fracturing of joints, which
with details and dimensions indicated. Saw cuts
may result in excessive opening at some joints.
Before sawing each joint, the concrete will be
shall be made to the depth indicated to insure that
cracking occurs as planned. Joints shall be constructed
examined closely for cracks, and the joints will not
by sawing a groove in the hardened concrete with a
be sawed if a crack has occurred near the joint.
power-driven saw.
Sawing will be discontinued in any joint where a
crack develops ahead of the saw cut.
(b.) Time. No definite time for sawing joints
(d.) Cuts. All areas of curing compound damaged
can be specified because of the many factors that
may influence the rate of hardening of concrete such
by the sawing operation will be resprayed. A cord
will be placed in the saw cut to retard evaporation of
as air and concrete temperatures during placement,
moisture.
ambient temperatures, weather conditions, curing
e. Special joints. The special joint shown in figure 3
and protection, cement content, and mix character-
for placing new concrete pavement adjacent to old
istics. The basic rule for satisfactory sawing is: "Be
concrete pavement requires special care. The concrete
prepared to saw as soon as the concrete is ready for
placed under the old pavement must be thoroughly
sawing regardless of the time of day or night. "
vibrated and must not be placed too rapidly or air
During warm weather, when most pavements are
voids will form under the old pavement. Use of a
constructed, the concrete usually will be ready for
water-reducing admixture to improve workability
sawing about 6 to 12 hours after placing. Since
may be helpful. Proper construction of this joint
concrete is placed mainly during daylight hours, a
requires special inspection of construction technique.
large portion of sawing will have to be done at night,
An alternate method of providing a load-transferring
and adequate lighting must be provided for this
joint when abutting old and new concrete pavements
purpose. Although a clean, sharp cut is desirable, a
is to drill and grout dowel bars into the vertical face
small amount of raveling at the top of the saw cut is
of the old pavement.
not objectionable when early sawing is necessary to
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