Figure 7-22.-Devices used to support horizontal reinforcing.
Location for Reinforcing Steel
The proper location for reinforcing bars is given
on the drawings.
To ensure that the structure can
withstand the loads it must carry, place the steel in
exactly the position shown. Secure the bars in
position so that they will not move when the concrete
is placed. This can be accomplished by using the
reinforcing bar supports shown in figures 7-22, 7-23,
Footings and other principal structural members
that are against the ground should have at least 3
Figure 7-23.-Precast concrete block used for reinforcing steel
Figure 7-24.-Beam-reinforcing steel hung in place.
inches of concrete between steel and ground. If the
concrete surface is to be in contact with the ground or
exposed to the weather after removal of the forms, the
protective covering of concrete over the steel should
be 2 inches for bars larger than No. 5 and 1 1/2 inches
for No. 5 or smaller. The protective covering maybe
reduced to 1 1/2 inches for beams and columns and
3/4 inch for slabs and interior wall surfaces, but it
should be 2 inches for all exterior wall surfaces.
The clear distance between parallel bars in beams,
footings, walls, and floor slabs should be a minimum
of 1 inch, or one and one-third times the largest size
aggregate particle in the concrete. In columns, the
clear distance between parallel bars should be a
minimum of one and one-half times the bar diameter,
one and one-half times the maximum size of the
coarse aggregate, or not less than 1 1/2 inches.
The support for reinforcing steel in floor slabs is
shown in figure 7-25. The height of the slab bolster is
determined by the concrete protective cover required.
Concrete blocks made of sand-cement mortar can be
used in place of the slab bolster. Wood blocks should
never be used for this purpose if there is any
possibility the concrete might become wet and if the
construction is of a permanent type. Bar chairs, like
those shown in figure 7-25, are available from
commercial sources in heights up to 6 inches. If a
height greater than 6 inches is required, make the