ASPHALT ANSWERS
If segregation is an issue on
your job, don’t forget to look
at the stockpile at the asphalt
plant for a quick answer.
Segregation
The Enemy
of Quality
TONY WIGHT
Many of us know there are a
multitude of problems and issues
that need to be avoided
when paving either a road,
commercial parking lot or a driveway.
Everything from water flow and slope
to texture and shadows in the mat.
One of the major challenges is putting
down a product that will hold up over
time. This requires starting off with a
solid base but it needs many things to
go well all the way to the top coat.
One downfall of many jobs is segregation.
Segregation is when the large
stones in our mix roll or separate from
the fines. This can sometimes be seen
as a spot where there are voids between
large stones. (No fines between the
larger stones.) This can allow water to
get into and under the layers of asphalt
and this can cause a failure in the finished
product.
Segregation will show up in several
forms, Truck End Segregation (one or
both sides), Center Line Segregation,
Joint or Edge Segregation and Random
Segregation. Segregation can start anywhere
from the way the plant builds its
stock pile to how fast or slow you run the
augers. Remember anytime you move or
convey material segregation can occur.
Truck end segregation takes two
forms. First, one-sided is normally
caused by improper loading of the
batcher at the plant but can happen
in loading the truck as well. Two-sided
truck end segregation is most often
caused from improper loading of the
truck when dumped from the silo. Remember
to take three drops in a tri-axle
and two drops from a tandem axle
truck. Truck end segregation can also
occur when dumping a new truck into
the paver. Try to remember to leave
some material in the hopper when
engaging a new truck. Less surging of
material into the hopper will help stop
segregation.
Centerline Segregation normally occurs
in the paver. Some pavers have a
center auger drive box that blocks the
material from falling directly down
in the center of the screed causing a
build-up of larger aggregate. This is
[10]
www.callape.com 1.800.210.5923