August 2013
CONSTRUCTION WORLD
38
The 50 storey high Carlton Centre, was officially opened in 1973 at a total
cost of over R88-million. Forty years later, it still stands proud as the
tallest building on the African continent. In 2012, an event of spalling
occurred which resulted in owners, Transnet Properties urgently
engaging SMEC Vela VKE Consulting Engineers for advice.
projects & contracts
ALTHOUGH JUST A SINGLE
piece of debris
had apparently fallen onto the roof of a steel
framed structure to the west of the Carlton
Centre, Vela VKE recommended that an
emergency restoration project be initiated.
Several products from Sika’s Concrete Repair
and Protection System were specified, given
their durability and cost effectiveness.
Due to the sheer height of the Carlton
Centre, which stands at 223metres, as well as
unpredictablewinds and atmospheric condi-
tions surrounding it, the highly experienced
SA Rope Access Company was awarded the
hazardous task of applying Sika’s high per-
formance products. The team chosen met
the challenge with great enthusiasm and
photographs of the workers seen suspended
from the roof bear testimony to their bravery.
Once preparations, which included chip-
ping away the contaminated and spalling
concrete as well as splicing the old rusted
rebar, were completed, repair work com-
menced. SikaTop-Armatec 110 EpoCem
(35 kits), a cement-based, epoxy-modified,
three-component, anti-corrosion coating and
bonding agent was used in conjunctionwith
Sika Rep LW (200 bags), a one-component,
non-sag, cement-based, multi-purpose
patching and repair mortar.
SikaTop-Armatec 110 EpoCem provides
excellent adhesion to concrete and steel
and acts as an effective barrier against
penetration of water and chlorides. It is an
outstanding bonding agent for subsequent
applications of Sika repair mortars, whether
cement or epoxy-cement based, andprovides
a high degree of mechanical strength. Con-
taining corrosion inhibitors, it is ideally suited
for repairs to concrete in which corrosion of
the reinforcing steel has occurred.
Sika Rep LW, used for cosmetic or structur-
al repair of deteriorated concrete or mortar,
can be applied onto interior, exterior, vertical
or overhead surfaces. It is easy to mix, apply
and finish, and while providing excellent ad-
hesion, is also shrinkage compensated. Sika
Rep LW is permeable to water vapour and of-
fers a high resistance to freeze/thaw cycling.
Cracks in the concrete were repairedwith
Sikadur-31 CF Normal (20 kits), a moisture-
tolerant, thixotropic, structural two-part
adhesive and repair mortar based on a com-
bination of epoxy resins and special fillers.
It is easy to mix and apply onto either dry or
damp concrete surfaces and hardens without
shrinkage. No primer is required when using
Sikadur-31 CF Normal and it is impermeable
to liquids and water vapour. Although used
for crack sealing on the Carlton Centre, this
versatile product is also suitable as a high
strength adhesive on awide range of surfaces
including concrete, ceramics, masonry, steel,
iron, aluminium, wood and glass. Further
advantages include high initial and ultimate
mechanical strength, aswell as good abrasion
and chemical resistance.
Sika FerroGard-903+ (1 000 litres), the
fourth product in the repair and protection
To the rescue of the Carlton Centre
system, was applied to treat the entire top
ream of the Carlton Centre. This treated area,
located on the fiftieth floor, covers the 360o
ObservationDeck, known as theTop of Africa.
Sika FerroGard-903+, a surface-applied,
mixed corrosion inhibitor, is based on organic
compounds designed to penetrate concrete
to forma protectivemonomolecular layer on
the surface of reinforcing steel. Penetration
depth can be tested on-site, using the Sika
“Qualitative Analysis Test”. Protection with
this innovative product delays the onset
and decreases the rate of corrosion, thereby
increasing service andmaintenance life cycles
by up to fifteen years. It is especially suitable
for extending the life of aesthetically valu-
able fair-faced concrete such as on historical
structures, as in this case, the Carlton Centre.
Complyingwith principle 11 of EN 1504-9
method 11.3, Sika FerroGard-903+ protects
both cathodic and anodic zones of reinforced
steel. It does not change the appearance of
the concrete structure and does not alter
the water vapour diffusion properties of the
concrete. Providing long termprotection and
durability, this product, which is easy and
economical to apply, can be used where no
other repair/prevention options are viable.
Due to the excellent workability char-
acteristics of the Sika products used in this
concrete repair and protection program, and
despite adverseweather conditions, contrac-
tors were able to complete the project within
the specified time schedule. Sika is justifiably
proud to have been chosen to supply its
state-of-the-art products to restore and pro-
tect an important South African landmark.
●
The 50 storey high Carlton Centre, was officially
opened in 1973 at a total cost of over R88-million.
Due to the sheer height of the Carlton Centre, which stands at 223 metres, as well as unpredictable
winds and atmospheric conditions surrounding it, the experienced SA Rope Access Company was
awarded the task of applying Sika’s high performance products.
