The Civil Engineering Contractor July 2018 | Page 18

ON SITE
Lined up along the stretch, the entire rig comprises a Vögele Super 1803-2 paver and the MT 3000-2 offset Power Feeder, with a truck
emptying its load into the paver hopper.
S
tretching 16 kilometres along
the N4, from Proefplaas to the
Solomon Mahlangu Interchange,
a road project is presently underway.
It forms part of South African
National Roads Agency’s (SANRAL’s)
preventative maintenance programme
and is being undertaken by KPMM,
a construction company specialising
in township infrastructure, road
construction, and road rehabilitation.
Key supplier to KPMM, is National
Asphalt, a specialist in asphalt
products to the construction, mining,
and building industries throughout
southern Africa. National Asphalt
is tasked with the manufacture and
supply of the asphalt used on the
project.
While the road is not new, there
have been interventions during its
life to ensure that it is maintained
as part of SANRAL’s maintenance
code. “Every five to 10 years, an
intervention generally must take place
to prevent roads from falling into
disrepair,” comments Dave Bennett,
general manager at National Asphalt.
Scope of work
The roadworks entail the resurfacing
and resealing of a section of one of the
busiest highways in Gauteng, as well
18 - CEC July 2018
as the rehabilitation of three over-
passes and four underpasses along
the 13-kilometre route. Included in
the scope of work is road-widening
along a section to provide access
to a proposed SANRAL/CSIR/UP
Transportation Research Centre.
The national route N4-01
generally consists of a six-lane dual
carriageway, which becomes a four-
lane dual carriageway near the Simon
Vermooten Interchange.
The total area to be resurfaced is
451 100m 2 and the project is estimated
to take 13 months, having started in
August last year.
The major component in this project
is the asphalt, which is manufactured
at National Asphalt’s Bonn Accord
branch in Pretoria.
The asphalt ‘recipe’
Neels Smith, operations manager
at National Asphalt, explains what
goes into making the fit-for-purpose
asphalt.
The plant produces the planned daily
quantity, says Smith and points out
that the company has both static and
mobile plants, supplying the industry
across the country.
“While we manufacture asphalt for a
variety of clients, each with their own
requirement,” says Smith, “for this
project, we produce 300-tons of A-E2
SMA per day.”
Aggregate and bitumen are the
ingredients for asphalt, with the
aggregate coming from a quarry
within a 30km radius, Smith explains.
“Different aggregate fractions are
required for the mix; it depends on
the ‘recipe’/specifications of the
project. Both ingredients are mixed
in a drum mixer at the asphalt plant.
It is heated to about 165°C and then
loaded onto the haulage trucks. The
lab at National Asphalt takes samples
of each truckload, which are subjected
to a battery of Marshall tests to
ensure that it has been manufactured
to the approved mix design. It is then
taken to the site and loaded into the
paving unit.”
National Asphalt has a process
laboratory where the final product
is tested to ensure that it complies
with and is within acceptable design
limits. Included in this process is
checking that the grading of the
aggregate complies with the desired
specifications of the mix for the
specific project. “The SMA for the
Proefplaas project consists of 10mm,
7.1mm aggregate and crusher dust
with binder content specified at