WINNING
QUARTZITE QUARRY SHINES
ENVIRONMENTALLY
By Eamonn Ryan
NPC Sterkspruit Aggregates is a combination quartzite aggregate quarry and adjacent ready-mix
concrete batch plant, operating as a subsidiary of Natal Portland Cement Company in the Outer
West area in Durban. Its tough quartzite has an especially high silica content.
A
vin Mandass, quarry manager
at NPC Sterkspruit Aggregate,
explains that the quartzite
aggregate mined at the
Sterkspruit Aggregate quarry – with its high
silica content – is an abrasive, hard material
which is only slightly less hard than other
quarry materials such as granite. “It breaks
easier but it’s very high wearing – so the
all the machinery and equipment has to be
exceptionally hardy.”
For dust suppression, Sterkspruit uses a
water tanker at the quarry and has water
sprays at different points in the plant. “The
process uses a lot of water and given the
drought that KwaZulu-Natal has recently
been through we try and minimise our
water consumption as much as possible. In
20_QUARRY SA| NOVEMBER/DECEMBER 2018
the quarry itself we’ve created a sump which
we use to supply the water tanker. For the
crushing plant we draw water from the
river. We are in the process of getting our
water use licenced. In 2010 we upgraded
our wash plant and one of the main criteria
upon which we based our final decision
was that it be able to recycle the water,” says
Mandass. “As a result, the quarry recycles
about 80% of the water it uses in its washing
process. We currently average 4 000m3 a
month. If it wasn’t for the recycling this
would exceed 10 000m3 a month.”
The standard practice at Sterkspruit is
that if there’s an issue with the plant, then
the plant is immediately shut down so that
it never runs empty for more than about
10 minutes. “We save electricity as far
as possible by, for instance, making sure
that the crushers are always running at
capacity. We monitor and benchmark our
electricity usage against our sister quarries
in South Africa and elsewhere in the world,
so that if any of them are controlling their
electricity consumption better than us
then we can learn from and follow their
example,” says Mandass.
Blasting process to extract rock
material
The quarrying process is divided into
different phases: drilling and blasting; load
and haul; crushing and stockpiling.
“We drill and blast by cleaning off the
bench and removing as much of the loose