BENEFICIATION
Dave Bennet, general manager of National Asphalt plant in Pretoria North.
asphalt road base that is found in the US
and Europe, so we do not have as much
asphalt to recycle.
“We are blessed with good road-
building materials and our weather is not
as cold, so our asphalt layers are much
thinner and the pavements are much
cheaper than European, American and
Australian pavements.”
In asphalt pavement recycling, materials
reclaimed from old pavements are
reprocessed along with new materials.
The three major categories of asphalt
recycling include:
very costly to repair.
“The risk is extremely high,” Says
Marais. As he describes it, a supplier
having won a contract may deliver 4 000t
(1 000t a day) of asphalt over the three or
four days before the test results come in
from the acceptance laboratory. If it does
not meet the specs, the whole job has to be
redone – including milling of the recently
laid road – at a cost of more than R1-
million per 1 000t rejected.
Higher costs of asphalt and aggregate
have compelled the industry to increase
efficiencies and to recycle old asphalt
pavements. Asphalt is the single most
recycled material in the US and in South
Africa almost all asphalt is also recycled
into new roads. However Marais explains
that South Africa does not use the thick
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• cold-mix recycling, where reclaimed
materials are combined with new
materials either onsite or at a central
plant to produce cold-mix base
materials; and
• surface recycling, a process in which
the old asphalt surface pavement is
heated in place, scraped down or
‘scarified’, remixed, re-laid and rolled.
Organic asphalt recycling agents may
also be added to help restore the aged
asphalt to desired specifications.
• hot-mix recycling, where reclaimed
materials are combined with new
materials in a central plant to produce
hot-mix paving mixtures;
Once the design is finalised, the plant produces a physical sample of that design to prove it can
actually be manufactured at the plant.
QUARRY SA | JANUARY/FEBRUARY 2019_35