UFC 3-270-03
15 March 2001
Figure 16.4. where the spall repair was conducted on both sides of the expansion joint. Note the
joint filler separating the spall repair.
16.6. Curing. Curing of the material is very important, especially for partial-depth repairs where
the surface-area-to-volume ratio of the repair area is larger than a full-depth repair, and bond
strength develops much slower than compressive strength. Rapid water loss from the surface
due to high temperature, low humidity, and/or windy conditions can result in severe shrinkage
cracking on the surface. Curing should consist of covering the patched area with two layers of
presaturated burlap which is then covered with clean polythylene sheeting. The burlap and
sheeting is then covered with wieghted plywood or form board. All cover layers should extend 12
inches (300 millimeters) beyond the outline of the patch. Covers should be removed, the burlap
resaturated, and the covers replaced daily for at least 7 days. The fresh PCC should be covered
as soon as possible after finishing the surface. Special curing procedures for rapid-setting
concretes must be followed to prevent excessive shrinkage cracking. These materials harden
rapidly and severe plastic shrinkage cracking may develop on the surface if the materials dry too
fast. Manufacturer's recommendations for curing of proprietary concretes must be followed.
16.7. Resealing. After the patch has cured, the final repair step is to replace the sealant to
maintain the existing joint or crack. Joint or crack resealing should not begin until the concrete
curing process is complete. The joint sealing operation is analogous to crack sealing. The joint
or crack adjacent to the spall is sawed out to the same width as the existing joint or crack using a
concrete saw, router, or hand saw. The joint filler must be removed by hand or by sawing. Joint
preparation should conform to the specifications outlined in Figure 3.6. The sides of the sawcuts
are then sandblasted, airblasted with compressed air, and washed with high-pressure water to
prepare a good surface for sealant adhesion. The area surrounding the repair should be swept
with a vacuum broom to remove debris, etc. After cleaning the area, backer rod is installed in the
joint or crack recess. For U.S. Army and Air Force facilities, the joint sealant employed must
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