DIGEST 2006 - Sabita

Graded stone seals
The seals that are being proposed
as generic low cost holding actions
on a road are typically made up of
a modified emulsion binder,
combined with a “slightly” graded
stone aggregate, such as a
combination of a 6.7 and 9.5mm
stone, or even a 4.75 and 6.7mm
stone. The graded effect of the
stone aggregate, together with the
Figure 3: Efficient use of graded stone and emulsion
binder for sealing cracks
low viscosity of the emulsion to fill
the cracks, achieves a result that
is not obtainable with conventional
surfacing systems (see figure 3).
Conventional seals
Apart from their ability to apply
graded stone seals, the machines
can be used for any of the
commonly known single or double
seals using up to 19mm sized
aggregates and conventional or
modified binders.
Since the arrival of their first unit
two months ago, a range of seals
totalling in excess of a 100,000 m 2
have already been completed.
These applications varied from
emulsion single and double seals,
(also using latex modified
emulsions) on municipal road
networks, as well as 80/100
penetration grade double seals.
While the on board computers
control the binder temperature
and maintain the application rates
of binder and aggregates within
tight tolerances,
(while digitally
recording the road
condition before
and after
application), there
are also a number
of other practical
aspects which
make surfacing
with these units
advantageous
vis-à-vis
conventional
chip-and-spray
techniques,
namely:
• Minimal aggregate loss in the
early life of the seal due to
instantaneous application
with the binder;
• Cost-effective sealing of
roads requiring remedial
treatment on distressed areas
only;
• Reduced traffic disruption due
to fewer construction vehicles
on the work site;
• More versatile and suitable
for sealing restricted areas
due to the high
manoeuverability, for
example at intersections;
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