The Civil Engineering Contractor March 2019 | Page 23

ON SITE
Sarel Holtzhausen, executive director
of Ceenex, says that a decision
was taken right from the outset
to construct the reservoir using
prefabricated concrete technologies
to accelerate construction times.
“Reservoir walls are an extremely
specialised undertaking. It would
have taken a specialist contractor
up to 14 months to complete using
cast-in-place methods without
the risk of having to correct the
construction of the walls or reseal
the structure. This is opposed to the
five to eight weeks using this new
system,” Holtzhausen says.
Rudi Bezuidenhout, Mbako
Projects & Trading, the main
contractor on this component of the
project, concurs: “The wall panels
were dispatched to site on a just-
in-time basis and then lifted and
placed by Corestruc’s team onto the
ring beam. This negated many of the
challenges associated with building
these walls using conventional in situ
techniques. These include the need
to establish tonnes of formwork and
coordinating the various teams, and
counting the steel fixers, shutter
hands, and concrete gangs.”
that were designed and manufactured
especially for this project.
Many hours were also invested in
the design of the four buttresses,
which contain numerous cast-in
components that were manufactured
in-house
using
computer-
numerically controlled machines.
They each weigh 11.4t and were
also lifted into place by Corehire, a
subsidiary of Corestruc.
Holtzhausen says that this modular
approach to constructing the walls
and roof of the structure is ideally
suited to rural areas that are not
adequately serviced by ready-mix
producers. “This is a real challenge
in rural areas. Ready-mix operations
tend to be located in the main urban
hubs where there is a higher demand
for the construction material. It
is simply not feasible to transport
ready-mix concrete over long
distances. The only other alternative,
therefore, would have been for the
contractor to batch its own concrete
on site — an option that would
have possibly prolonged construction
times and required further extensive
quality controls.”
Holtzhausen says that the
technology also provides a more
cost-effective means of constructing
larger structures than in situ
techniques. This is where the real
value of the system will be realised,
considering the growing backlog in
water infrastructure and the pressure
municipalities are under to better
manage their dwindling budgets.
Works started on the foundations
and bases for the columns of the roof
which, once completed, was followed
by the ring beam and the walls, and
Specialist activity
While Mbako did the surrounding
water infrastructure of the project,
as well as the floor and ring-beam of
the reservoir, Corestruc designed and
manufactured the wall system that
is being used in combination with
its tried-and-tested roof technology.
The latter has been used to assist
in quickly delivering structures as
large as 50Mℓ in rapidly expanding
metropolitan municipalities.
As a specialist subcontractor to
Mbako Projects & Trading, it was also
tasked with installing the modular
roof and wall system on site. The wall
system comprises 60 precast concrete
panels, each weighing eight tonnes,
9.8m in length and 16.4m in width.
This is in addition to four buttress
panels, each weighing 11.4t. They were
produced by Corestruc using forms
www.civilsonline.co.za
The process of pre- and post-tensioning is what keeps the structure monolithic.
CEC March 2019 | 21