scarifying and retreatment the second year will produce
a thicker and stronger surface.
WARNING
Before planning any road oiling work your
supervisor should check with local authorities
concerning environmental protection restric-
tions.
Aggregate Surface Treatment
The sprayed asphalt with aggregate cover surface
treatments are applications of liquid asphalt, followed
by an application of aggregate. This can be done in one
or more layers of construction. Two types of sprayed
asphalt with covered aggregate surface treatments are in
use today: single- and multiple-surface treatments.
SINGLE-SURFACE TREATMENT.— Single-
surface treatments are thin, bituminous-aggregate
toppings, applied to existing bases or surfaces, such as
concrete or asphalt. Construction involves applying a
bituminous prime or tack coat to the base or surface.
This coating is followed by an application of bitumen
and small-sized aggregate. Single-surface treatments
are sometimes called seal coats, because they seal the
surface of the road or runway.
Sequence of Operations.— Figure 16-28 shows the
sequence of operations for the application of a
single-surface treatment.
The first steps, such as
sweeping, priming or tacking, and curing, are the same
as those used for applying a prime coat. The binder
(bituminous material) is applied over the prime coat
with an asphalt distributor. The aggregate is then spread
over the binder by use of aggregate spreaders. The
aggregate cover is spread uniformly immediately
behind the distributor.
As soon as the aggregate is
spread, it is pushed into the soft asphalt by rolling it with
a pneumatic-tired roller.
Binder Application.— When you are applying the
binder, it should be hot enough to spray properly and
Figure 16-28.-Sequence of operations for the application of a single-surface treatment.
16-24
