Haunch boards (side forms on girders and beams)
and wall forms can usually be removed after 1 day.
Column forms usually require 3 days before the forms
can be removed. Removal of forms for soffits on
girders and beams can usually be done after 7 days.
Floor slab forms (over 20-foot clear span between
supports) usually require 10 days before removing the
After removing the forms, the concrete should be
inspected for surface defects. These defects may be
rock pockets, inferior quality ridges at form joints,
bulges, bolt holes, and form-stripping damage.
Experience has proved that no steps can be omitted or
carelessly performed without harming the
serviceability of the work. If not properly performed,
the repaired area may later become loose, crack at the
edges, and not be watertight. Repairs are not always
necessary, but when they are, they should be done
immediately after stripping the forms (within 24
Defects can be repaired in various ways.
Therefore, lets look at some common defects you
may encounter when inspecting new concrete and
how repairs can be made.
RIDGES AND BULGES. Ridges and bulges
can be repaired by careful chipping followed by
rubbing with a grinding stone.
HONEYCOMB. Defective areas, such as
honeycomb, must be chipped out of the solid
The edges must be cut as straight as
possible at right angles to the surface or slightly
undercut to provide a key at the edge of the patch. If
a shallow layer of mortar is placed on top of the
honeycomb concrete, moisture will form in the voids
and subsequent weathering will cause the mortar to
span off. Shallow patches can be filled with mortar
placed in layers not more than 1/2-inch thick. Each
layer is given a scratch finish to match the
surrounding concrete by floating, rubbing, or tooling
or on formed surfaces by pressing the form material
against the patch while the mortar is still in place.
Large or deep patches can be filled with concrete
held in place by forms.
These patches should be
reinforced and doweled to the hardened concrete
(figure 7-54). Patches usually appear darker than the
surrounding concrete. Some white cement should be
used in the mortar or concrete used for patching if
appearance is important. A trial mix should be tried to
determine the proportion of white and gray cements to
use. Before mortar or concrete is placed in patches,
the surrounding concrete should be kept wet for
several hours. A grout of cement and water mixed to
the consistency of paint should then be brushed into
the surfaces to which the new material is to be
bonded. Curing should be started as soon as possible
to avoid early drying. Damp burlap, tarpaulins, and
membrane-curing compounds are useful for this
BOLT HOLES. Bolt holes should be filled with
small amounts of grout carefully packed into place.
The grout should be mixed as dry as possible, with
just enough water so it compacts tightly when forced
into place. Tie-rod holes extending through the
concrete can be filled with grout with a pressure gun
similar to an automatic grease gun.
ROCK POCKETS. Rock pockets should be
completely chipped out. The chipped out hole should
have sharp edges and be so shaped that the grout patch
will be keyed in place (figure 7-55). The surface of
all holes that are to be patched should be kept moist
for several hours before applying the grout. Grout
should be placed in these holes in layers not over 1/4
inch thick and be well compacted. The grout should
be allowed to set as long as possible before being used
to reduce the amount of shrinkage and to make a
better patch. Each layer should be scratched rough to
improve the bond with the succeeding layer and the
last layer smoothed to match the adjacent surface.
Figure 7-54.-Repair of large volumes of concrete.