spaces enclosed by previously constructed
FORMS. These forms are usually removed once
the plastic concrete hardens into the shape
outlined by the forms.
Forms for concrete structures must be tight,
rigid, and strong. If the forms are NOT tight, loss
of water and paste may cause sand streaking as
well as weakness to the concrete. The forms must
be strong enough to resist the high pressure
exerted by the concrete.
Form Materials
Undisturbed soil or clay, if sufficiently rigid
and excavated to proper dimensions, maybe used
as EARTH FORMS. Design, specifications, and
construction methods, however, dictate what kind
of form materials are to be used on certain
structures. Wood, plywood, steel, fiber glass, and
other approved materials are commonly used as
form materials. Forms for concrete pavement and
curves should be metal; surfaces exposed to view
in the finished structure and those requiring
special finishes should be wood, plywood, or
other approved material.
Figure 7-28.-Form for concrete column.
Foundation Forms
Foundation forms may include forms or parts
of forms for column footings, pier footings, and
wall footings. Whenever possible, the earth should
be excavated and the hole used to contain the
foundation of footing forms. In most cases,
FOOTINGS are cast directly against the earth,
and only the sides are molded in forms. In some
cases where there is a firm natural earth surface
that is capable of supporting and molding the
concrete, parts of forms are often omitted.
Figure 7-26 shows a typical large footing form.
Figures 7-27 and 7-28 show typical footing forms
for a concrete pier and a concrete column,
respectively.
Wall Forms
Wall forms are made up of five basic parts.
They are as follows: (1) sheathing, to shape and
retain the concrete until it sets; (2) studs, to form
a framework and support the sheathing; (3) wales,
to keep the form aligned and support the studs;
(4) braces, to hold the forms erect under lateral
pressure; and (5) ties and spreaders or tie-spreader
units, to hold the sides of the forms at the
correct spacing (fig. 7-29).
Wall forms may be built in place or pre-
fabricated, depending on the shape and the
desirability for reuse.
Wall forms are usually reinforced against
displacement by the use of TIES. Two types of
Figure 7-29.-Parts of a typical wall form.
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