BENEFICIATION
Preparing for a days production.
slabs, bridges, grand stands, and reservoirs
because we do it every day. However,
with work being scarce at the moment we
have to take what we can get and build in
contingencies for that learning curve,” he
says.
Each delivery from the on-site batch
mix is put through a slump test or more
recently, it has gone for the flow test
on every mix, where a margin of 750 is
accepted. “We do get rejects even though
we have a sophisticated system, as most
of the glitches are water related. However,
with experience, our workers can
increasingly adapt to variances and still
work with a margin above 750 rather than
reject it. The concrete we mix is a durable
concrete — we use a SCC mix that gives us
90Mpa on a beam that is actually designed
for 35Mpa. It is our choice, and is more
expensive — but we do it for a superior
end product.”
The batch mix produces roughly
2 000t a month of concrete, or 850m3, at
the moment, which is not full capacity.
De Bruin emphasises that the tonnage
produced is a factor of the type of product
being manufactured at a moment in time,
with some containing high volume and
others much less. Of greater relevance is
the rand value being produced.
32_QUARRY SA | MAY/JUNE 2019
“We manufacture bridge beams 15m long,
weighing five tonnes each, but in the past,
we’ve done 15m bridge beams weighing
20t each. That’s what pushes up tonnage
because it takes the same time to shutter,
handle, and cure — the only difference
is the pouring time. The batch plant is
currently running a single nine-hour shift,
down from two shifts, because there is
not enough work. We have in the past run
the batching plant 24 hours a day, but not
now.”
Marketing potential
of precast
De Bruin says that during the past decade,
precast products have grown considerably
in popularity among civil engineering
contractors and consultants. “Ten years
ago it was difficult to persuade engineers:
where five years ago we had to convince
consultants to use precast, today they
make their building designs with precast
in mind, often because the client wants to
speed up delivery — with no convincing
necessary today from our side.
“The major advantage of precast is
decreased construction time and the
high quality of the product, because it is
manufactured under controlled conditions
“There are standard
moulds for certain
products, as stadia and
reservoirs for instance
typically have the same
specced products, and the
moulds can consequently
be repeatedly reused.”
in a factory. It’s already quality controlled
and known to meet specifications, and
they get it when they want it. When they
are ready for the beams, they receive it on
that day,” explains De Bruin.
Where South African construction
is headed is perhaps revealed by trends
overseas, where precast is more commonly
used. De Bruin says South Africa is fast
catching up to that level of usage, “faster
than we would have ever anticipated”.
De Bruin says precast manufacturing is
competitive. CoreSlab competes against
many smaller rib-and-block suppliers in
Limpopo that supply both the residential
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