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CAPITAL EQUIPMENT NEWS
JANUARY 2017
16
I
t is proven that aggregate and
temperature segregation in hot
mix asphalt is mostly the root of
poor quality roads. In circumstanc-
es where the mix has material or
temperature segregation, the pavement
will have areas with poor structure and
texture. Large temperature differentials
within the mix are prevalent during long
hauls from the batching plant to the site
or during colder days. As a result of long
haul distances from a batching plant to a
site, the top layer of the asphalt mix in the
truck bed can have temperature variances
of up to 50oC when compared with the rest
of the material. Non-uniform compaction,
ravelling, stripping and potholes can all be
traced back to these temperature differen-
tials in the mat.
Studiesinpavementfailurehavealsoshown
that a major cause is material segregation. In
conventional road construction a truck dumps
material directly into the hopper of the paver.
As the truck dumps the hot mix asphalt
directly into the paver hopper, aggregates
in the mix separate, changing the overall
asphalt mix, causing material segregation.
When segregated material is laid down
on the pavement, it is compacted with
poor structure or texture and eventually
the mat lacks uniform density, causing
the pavement to fail prematurely. The
gradation of the aggregate and uniformity
of the asphalt mix are both very important
considerations for mix stability and road
mat structure.
To deal with these challenges, in 2012,
the South African National Roads Agency
(Sanral) decided to specify a material
transfer vehicle on all its road contracts
of 2 000m² and more. The road principal
reasoned that the conventional method
of having a truck feeding directly into the
paver constituted many quality flaws that
ROAD TO QUALITY PAVEMENTS
The conventional methodology of having a truck tipping directly into the paver
constitutes many quality flaws that translate into excessive maintenance costs
over the lifecycle of the pavement. To address this setback, in 2012, Sanral
compelled the use of a material transfer vehicle on most of its road contracts,
and this technology weighs in with key benefits that translate into reduced
maintenance costs over the lifespan of a pavement, writes
Munesu Shoko
.
“Most of the contractors we carried out trials
with have since purchased our material transfer
vehicle. This was also aided by our ability to meet
and exceed Sanral’s expectations as far as the
specifications are concerned.”
With its large receiving hopper that can hold more than 16 t, the Vögele MT 3000-2
Offset ensures continuous paving, doing away with stop/starts of the paver.