Civil Engineering Reference
In-Depth Information
There have been few, if any, major changes in the prin-
ciples of conveying concrete during the last 75 years. What
has changed is the technology that led to development of
better machinery to do the work more efficiently. The
wheelbarrow and buggy, although still used, have
advanced to become the power buggy (Fig. 10-8); the
bucket hauled over a pulley wheel has become the bucket
and crane (Fig. 10-9); and the horse-drawn wagon is now
the ready mixed concrete truck (Figs. 10-10 and 10-11).
Fig. 10-10. Ready mixed concrete can often be placed in its
final location by direct chute discharge from a truck mixer.
(54955)
Fig. 10-8. Versatile power buggy can move all types of
concrete over short distances. (54088)
Fig. 10-11. In comparison to conventional rear-discharge
trucks, front-discharge truck mixers provide the driver with
more mobility and control for direct discharge into place.
(70006)
Years ago concrete was placed in reinforced concrete
buildings by means of a tower and long chutes. This was
a guyed tower centrally placed on the site with a hopper
at the top to which concrete was hauled by winch. A series
of chutes suspended from the tower allowed the concrete
to flow by gravity directly to the point required. As con-
crete-framed buildings became taller, the need to hoist
reinforcement and formwork as well as concrete to higher
levels led to the development of the tower crane—a
familiar sight on the building skyline today (Fig. 10-12). It
is fast and versatile, but the fact that it has only one hook
must be considered when planning a job.
The conveyer belt is old in concept and much changed
over the years (Fig. 10-13). Recently, truck-mixer-mounted
conveyor belts have come into use (Fig. 10-14). The pneu-
matic process for shotcreting was patented in 1911 and is
Fig. 10-9. Concrete is easily lifted to its final location by
bucket and crane. (69687)
