TM 5-822-9/AFM 88-6, Chap.10
15. Procedure for condition 5. The repairs
slab using air hammers. All joint sealant material
inside the repair area should also be removed. All
required under condition 5 (fig. 1) include all spalls
exposed vertical faces within the repair area should
which occur along joints and along working cracks.
be cleaned. Prior to the placement of the new
The same general procedures as mentioned for
concrete, the exposed subgrade should be
condition 3 are used for the repair of isolated small
reconditioned to comply with the specified require-
surface spalls or popouts. The repair of all spalls
ments.
consists of removing unsound or damaged
concrete, modifying the spall cavity dimensions as
new concrete to adjacent slabs at the joints, the
necessary to prevent further breakout, taking pre-
vertical faces should be protected with a bond-
cautions in the repair procedure to ensure freedom
breaking medium. The existing contraction joint
of movement at working joints, and taking appro-
may be maintained by the use of temporary inserts
priate measures to properly seal the joint. Large
of appropriate dimensions or by sawing the
spall areas should be repaired using PCC bonded
required kerf. Sawing must be done early enough to
with the proper epoxy resin system. "Popouts" are
prevent development of a random crack at the joint.
not normally repaired unless hazardous to tires. If
c. Placement of new concrete. After removing
they are determined to be hazardous to tires, repair
the concrete and preparing the subgrade, the
with epoxy resin systems.
cleaned vertical surfaces should be coated with at
a. Removing unsound or damaged concrete. All
least a 20-mu film of the epoxy resin system, using
unsound or damaged concrete must be removed
a stiff bristle brush or roller to ensure thorough
prior to repairs. The defective areas to be removed
wetting of the concrete. Placement of the new
can be determined by tapping with a hammer or
concrete should be delayed until some degree of
steel rod throughout the area and listening for dull
tack has developed (30 minutes to 1 hour). When
or hollow sounds. The Schmidt hammer can be
vibrators are used, it is essential to allow the epoxy
used by those experienced with this test. A tensile
test that can be used in the field to check the
bond coat to reach a tacky state since vibration can
soundness of the substrate concrete has been
displace the epoxy from the existing concrete by
suggested in the American Concrete Institute (ACI)
emulsifying the fluid epoxy bond coat. Vibrators
Committee Report 503; the test is designated as a
should not come in contact with the epoxy coating.
"Field Test for Surface Soundness and Adhesions."
If the concrete placement is delayed until the epoxy
The periphery of the area required to be removed
coating reaches a soft rubberlike stage, a second
should be sawed to a depth consistent with the type
application of epoxy bond coat equal to the amount
of repair. Saw cutting delineates the repair area and
of the first coat should be applied to the existing
serves to essentially eliminate edge spalling and
bond coat. If the concrete placement is delayed
weakness that might be introduced by outlining the
until the epoxy coating is no longer tacky, the
repair area with other types of equipment. The saw
epoxy coating will have to be removed or abraded
cut lines should be located outside the defective
by sandblasting and a fresh coat applied. Forms, if
area and in sound concrete. The saw cut should not
needed, should be placed after the concrete
be extended across the joint into the adjacent slab
pavement has been properly prepared. The forms
unless that area is also spalled. The depth of the
should be lined with polyethylene sheets or waxed
saw cut should be at least inch for epoxy resin
paper to prevent any adhesion to the form that may
mortar repairs and 2 inches for epoxy resin
result from the override of epoxy onto the form.
concretes and epoxy resin bonded PCC. In
preparing cutouts for popouts or small spalls
The use of form oil will not be permitted. The
wholly within a structural component and not
concrete mixture should be relatively dry and the
involving joints; edges, or corners, featheredging is
slump of the concrete should not exceed 2 inches.
permissible. The feather-edge should be at least 1/4
Placement, consolidation, finishing, and curing of
inch deep to provide a shoulder of sufficient depth
the concrete are accomplished by normal
to obtain a smooth finish. High-frequency chipping
procedures, as specified in TM 5-822-7. The repair
hammers can be used to make cutouts for this type
is to be finished so as to match the texture of the
of repair in lieu of saw cuts. Concrete removal
surrounding concrete. After the concrete has cured,
inside the saw cut should be accomplished using
the reconstructed joints should be sealed in the
medium to lightweight air hammers. The bottom of
conventional manner.
the cutout should be smooth in order to reduce the
14. Procedure for condition 4. The repairs
surface area and therefore reduce the quantity of
required under condition 4 do not use epoxy resin
epoxy resin concrete needed for the patch. Also, in
grouts, mortars, or concrete.
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