MINE EXCURSION
Despite adverse economic conditions, African Spirit Trading (AST) Sand
Mines’ operation close to Cullinan, in Gauteng, South Africa, has gone from
strength to strength, writes Leon Louw.
A
ST Sand Mines’ Van Dykspruit quarry is on the doorstep
of Petra Diamonds’ Cullinan mine in Gauteng. Cullinan
is currently expanding their underground operations,
which requires a signifciant amount of high-quality sand
and aggregates for their structural concrete. According to Oliver
Blackmore, the mine general-manager, the mine delivers more than 3
000 tonnes of high grade silica sand to Cullinan’s batching plant per
month. In the batching plant, the sand is mixed with quartzite stone
and cement to produce an extremely strong 72MPa concrete that is
pumped to the workings more than 2km undergound, where it is used
mostly in spraycrete to strengthen the integrity of newly developed
underground tunnels. The concrete is also used for causeways and
other infrastructure both underground and on surface.
Blackmore says that the resource at Van Dykspruit is low in clay content
and therefore ideal for the type of product Cullinan demands. “If the sand
contains a high percentage of clay, the concrete requires more water
and cement, increasing the client’s costs substantially. After
processing the run-of-mine sand, the silica sand at
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VanDykspruit contains only 2.4% of materials passing 75µ making the
processed sand a higher quality in comparison to other sand deposits in
the area,” Blackmore explains.
Suppying Cullinan with sand is not the only market for AST’s silica and
quartzite. The mine was initially developed because of its strategic
location close to the rapid urban sprawl of Pretoria East and the
township of KwaMhlanga. Furthermore, the construction of the Moloto
corridor road, which will run from Pretoria to KwaMhlanga, is expected
to generate increased demand for road construction materials, and AST
is gearing up to supply all the industry requirements in the area.
Quartzite the next target
Surface lying sandstone currently
being mined and processed
at Van Dykspruit, overlies a
bedrock of quartzite that will
be crushed down to a product size
that can be used as roadstone. The mine had
their inaugural blast in June with the aim to access
the bedrock quicker, enabling the company to diversify its
product range. Having mined the weathered loose top layers of silica
sand, AST decided to drill and blast making it easier to mine the more
competent sandstone mechanically, allowing the resource to be mined
more efficiently and in greater quantities.
African Mining
African Mining September 2019
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