The Civil Engineering Contractor May 2019 | Page 18

ON SITE: PROJECT 1
Soya processing plant steel erection in the foreground with MySilo soya silos in the background.
adjacent industrial sites were piled,
but those structures are more
substantial), though we eventually
went with dynamic compaction
below all the silos, the boilers, and
the new soya processing plant. This
wasn’t necessary for the roads.”
Maitre explains this process: “We
used large cranes to lift a 12.5t block
of steel and repeatedly dropped it
from a height of 22m. That gives
you good foundation bearing for a
depth in excess of 12m. We were
looking for good bearing for 8m to
12m and they achieved it. This adds
considerably to the costs — it took
two rigs and was time-consuming.
The result was that a lot of the
silos arrived before we were ready
and had to be stored in warehouses
until we had the concrete bases in
readiness. We have avoided this aspect
with the boilers, despite the rains we
have been having recently [February/
March].”
An unexpected plant shutdown
required maintenance of the solvent
plant. This was scheduled at short
notice and was under way at the time
of the Civil Engineering Contractor visit.
Maitre says this presented an ideal
opportunity to commence work on
the solvent plant and surrounds —
but also required ADA to complete
16 | CEC May 2019
all its design work and client briefings
within three weeks to facilitate work
during the plant downtime.
“This made it a project within a
project, as we had to complete all this
work within the four-week shutdown
window,” he says.
Concrete
longevity
roads
for
Of interest is that the developers have
opted for an entirely concrete road.
“Because the site will be extensively
developed, the high traffic load
of trucks will be using hydraulics
and manoeuvring in tight spaces
— putting extra wear on the road
surface. Hence, we preferred heavy-
duty concrete to asphalt or paving.
The loss of any downtime due to
road wear and tear would cost the
production process far in excess of
any additional upfront cost of road
surfacing.”
Coincidentally, says Maitre, concrete
roads are one of his personal particular
interests, having written his university
thesis on the subject and he liaised with
The Concrete Institute’s Bryan Perrie on
it many years ago. “Ever since then, I’ve
had a passion for concrete slabs on the
ground. The failures are extensive and
well documented. I interacted closely
with Bryan on ultra-thin concrete layers
they’ve been investigating of late, and
after thorough discussion, we went for
conventional un-reinforced concrete.
We’re casting right now in the harshest
of climatic and weather conditions: in
the heat of summer and also during high
rainfall, both of which can compromise
concrete road construction. We
concentrate on testing of the factors that
can compromise concrete — making
sure it has as low a water content as
possible, the lowest slump as practically
possible, but at the same time still
practical from a workability point of
view. We dictated that the ready-mix
supplier takes a slump test of every
single ready-mix concrete truck coming
in, and any truck that was in excess of
100mm was sent away.”
Ready-mix suppliers have standard
mixes that have been tested, but
conditions of rain and temperature
can cause variances, causing variable
slump results due to wet sand and
stone in the mix. Too much moisture
can cause shrinking and cracks in the
concrete — “We want to avoid that
upfront. Often people don’t fully
realise that concrete on the ground
has a very high risk of failure.
“Innocuous as pouring concrete on
the ground may seem, there’s a whole
range of factors which influence the
outcome: moisture on the ground,
www.civilsonline.co.za