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CONSTRUCTION WORLD
APRIL
2015
Having
successfully
designed
the bridges for the Gillooly’s
Interchange in Gauteng, one of
the busiest interchanges in the
southern hemisphere, consulting engi-
neers, Hatch Goba were commissioned by
SANRAL in 2009 to design an upgrade for
the old split-diamond, signalised intersec-
tion between the N2 (National Road) and
the M19. The new design was for a free-flow
directional four-level systems interchange;
involving the construction of five new
bridges and two pedestrian bridges, with
two incremental launch bridges as promi-
nent features. The project was awarded to
main contractors Rumdel Cape and Mascon.
As both highways comprise major traffic
routes, the emphasis on this project was
to keep traffic disruption to an absolute
minimum. Additional challenges were space
constraints caused by the nearby Umngeni
River and the adjacent residential and
commercial developments. The standard
segmental method of bridge building for
two directional ramps at the intersection
was therefore scrapped in favour of the
innovative method known as incremental
launch. This method entails building the
entire bridge deck from one end of the s
tructure and eliminating the need for
formwork, thereby allowing traffic flow to
continue uninterrupted.
The incremental launch technology
involves sliding sections of bridge deck over
special bearings, which are
concrete blocks covered with
stainless steel and reinforced
elastomeric pads. The first
such bridge constructed was
232 m long, from Umgeni Road
onto the N2 Northbound while
the second one measured
205 m long from the N2 North-
bound onto Umgeni Road.
Metier Mixed Concrete
supplied shotcrete for rock
stabilisation of the Umgeni
on-ramp to the N2 South-
bound. Two Sika products
were added to the shotcrete:
SikaPlast V210, an aqueous polymer solu-
tion that is a multi-purpose water reducer
and superplasticiser, and SikaTard-930, a
retarding concrete admixture developed for
the control of cement hydration. It can be
used in wet or dry spray shotcrete where
cement hydration of the concrete mix is
prevented (for up to three days, if required).
Other Sika products supplied were:
Sikadur-31 CF Normal was used on the base
plates of the columns supporting the incre-
mental launch to be used for the launch
bridges. As a concrete curing compound,
Sika Antisol-E was sprayed onto all bridge
decks and columns to prevent premature
water loss. Rugasol-2-Liquid was applied on
all concrete pours to prevent cold joints and
to allow a keyed surface for new concrete.
Exposed rebars were protected by SikaT-
op-Armatec 110 EpoCem, an anti-corrosion
coating and bonding agent that provides
excellent adhesion to steel and concrete.
Sika AnchorFix-3+ was used for bonding the
rebars. SikaGrout-212 and Sika Rep LW were
used for concrete repairs.
When construction on the R352-million
project commenced in March 2011, three
of the neighboring communities benefitted
greatly as local labour was used to fill 150
newly created jobs. The Umgeni Interchange
upgrade, which is nearing completion, will
significantly alleviate traffic congestion
by allowing the free flow of approximately
14 000 vehicles during morning peak hour
and approximately 16 000 vehicles during
afternoon peak hour.
By supplying numerous dependable,
innovative products, Sika has played a vital
role in this project. As one of the largest
undertakings of its kind in South Africa,
Hatch Goba believes it will set an interna-
tional benchmark for any similar projects in
the future.
>
in Durban interchange upgrade
VITAL ROLE
The massive R352-million Umgeni interchange upgrade
currently in progress along one of Durban’s arterial routes
will be a feat of engineering skill when completed. Sika was
proud to supply a varied selection of their internationally
renowned products for this multi-bridge construction project.
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