Figure 4-55. Spreading cold mix with conventional paver.
Figure 4-56. Spreading cold mix with full-width cutter-trimmer
modified for paving.
Figure 4-53. Stationary cold-mix plant.
flow of mixture from the haul truck to the
spreader must be maintained. Towed-type spread-
ers are attached to the rear of haul trucks (fig
4-58). The asphalt cold mix is deposited into the
hopper and falls directly to the surface being
paved. As the truck moves forward, the mixture is
struck off by a cutter bar, a blade, or by the screed
and is ironed out by the screed or by rollers. Many
Figure 4-54. Flow diagram of a typical
towed-type spreaders have floating screeds. In
cold-mix continuous plant.
order for the spreader to start out spreading to full
depth, blocking should be placed under the screen
volatiles without aeration by manipulation, a con-
before any mixture is dumped into the hopper. The
ventional self-propelled asphalt paver may be used
hopper should be kept full of material during
to place asphalt cold mixture (fig 4-55). A full-
paving operations to ensure a full, even spread.
width paver may be used if the plant can produce
The spreader should be towed at a uniform speed
enough mixture to keep the paver moving without
for any given setting of the screed or strike-off
start-stop operation (fig 4-56).
gate. Variations in towing speed will vary spread
(b) Spreaders. Spreading equipment such as
d. Central Plant Mix Construction.
the Jersey Spreader and towed spreaders are
(1) Preparation of mixture. In batch-type
commonly used. The Jersey Spreader is a hopper,
plants, mixing is usually accomplished by a twin-
with front wheels, that is attached to the front end
shafted pugmill having a capacity of not less than
of a crawler or rubber-tired tractor, into which the
2,000 pounds. The correct amounts of asphalt and
asphalt mixture is dumped. The mixture falls
aggregate, generally determined by weight, are fed
directly to the road and is struck off and spread to
into the pug-mill. The batch is then mixed and
controlled thickness (fig 4-57). To begin spreading
discharged into a haul truck before another batch
the mixture at the specified depth, the tractor
is mixed. In the continuous-mixing plant, the
should be driven onto blocks or boards of a height
devices feeding asphalt, aggregate, and water, if
equal to the depth of spread and placed so that the
needed, are interlocked to maintain automatically
tractor will ride directly onto the newly-placed
material. Once spreading has begun, a continuous