UFC 4-150-07
19 June 2001
CR-8: TYPICAL CONCRETE WALL REPAIR
Problem: Holes or severely deteriorated areas require replacing the wall section
with cast-in-place concrete.
Description of Repairs: Defective section of wall is removed, surfaces and
reinforcing steel are prepared, form work built, and wall is restored with cast-in-
place concrete. Repair may be an internal section, as shown in Figure 7-7, or
may be the top of a wall or pier deck curb requiring an open-top form. Equipment
used includes: sandblasting and air-water jet cleaning equipment, concrete saw,
air chipping hammer, air-suction gun for mortar if available, power vibrator and
tamper, and conventional concrete placement tools.
Materials: Portland cement concrete with maximum shrinkage of 0.05 percent.
Preparation:
a. Use air hammer or hand tools to remove all unsound concrete to
the limits of the repair area.
b. Cut the top edge of the hole at the face of the structure to a fairly
horizontal line (see Figure 7-7). Where a hole passes through a structural
element, it may be necessary to fill the hole from both sides. In this case the
slope of the top of the cut should be modified accordingly.
c. Cut the bottom and sides of the hole sharp and square with the
face of the wall. When the hole goes entirely through the concrete section,
spalling and feather edges can be avoided by having chippers work from both
faces. All interior corners should be rounded to a minimum radius of 25 mm (1
inch).
d. Do not leave reinforcing steel partially embedded. Ensure there is a
minimum of a 25 mm (1 inch) clearance around each exposed bar. Remove
unnecessary tie wires.
e. Clean all surfaces to bond to new concrete with wet sandblasting
and air-water jet. Clean exposed steel with abrasive blasting or wire brushing.
Repair Procedures:
a. Construct front forms for patches more than 46 cm (18 inches) high
in horizontal sections so the concrete can be placed in lifts not more than 30 cm
(1 foot) high. The back form can be built in one piece. Sections to be set as
concreting progresses should be fitted before concrete placement is started. See
Figure 7-7.
b. For irregularly shaped holes, chimneys (accesses) may be required
at more than one level. In some cases, such as when beam connections are
7-36
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