Construction World November 2015

CONSTRUCTION WORLD

NOVEMBER

2015

ADMIXTURES

When the City of Cape Town

decided that 9 Dorp Street, one

of the most renowned modernist

buildings in the area needed a

facelift, BVI Consulting Engineers specified

over ten Sika products for the project and

awarded the contract to The Construction Co.

Products used

Repair of concrete spalling was achieved

using products from Sika’s Concrete Repair

and Protection range; SikaTop Armatec-110

EpoCem, two ready-to-use mortar prod-

ucts and SikaGrout-212. SikaTop Armatec-

110 EpoCem, a cementitious, epoxy resin

compensated three-component coating

material containing a corrosion inhibitor, was

used as a bonding primer and reinforcement

corrosion protection.

It provides excellent adhesion to

concrete and steel and is suitable for control

of anodic areas. With good resistance to

water and chloride penetration, SikaTop

Armatec-110 EpoCem provides extended

open times for repair mortars and may be

applied by brush or spray gun.

Sika MonoTop-610, a cementitious,

polymer modified one-component bonding

slurry with active corrosion inhibitors, was

used as primer prior to the application of

Sika MonoTop-615 HB, a high-build, polymer

modified repair and reprofiling mortar,

containing silica fume. Designed for thick

layer concrete repairs, its excellent worka-

bility characteristics and thixotropic behav-

iour were ideal factors for this project. Both

MonoTop products provide good resistance

to water and chloride penetration and are

sprayable by the wet spray method.

Since 9 Dorp Street carries considerable

architectural significance, heritage archi-

tects who have earmarked the building for

heritage status, required numerous samples

of the Sika repair mortars in order to obtain

the closest possible colour match to the

existing concrete.

High performance, cement-based

SikaGrout-212 completed the spalling repairs.

A fluid grout that expands by gas genera-

tion whilst in the plastic state of curing, it

provides rapid strength development and

high final strengths. It is non-corrosive and

shrinkage compensated.

Passivation

For passivation of the reinforcing steel, Sika

FerroGard-903+, a Migratory Corrosion

Inhibitor (MCI) was applied to all repaired

concrete surfaces. Based on organic

compounds, it penetrates the concrete to

form a monomolecular layer on the surface

of the reinforcing steel, protecting both

cathodic and anodic zones.

Sika FerroGard-903+ does not alter the

appearance of the concrete or the water

vapour diffusion properties of concrete.

This simple to use, economical

product can be applied where other

repair or prevention options are not

viable, and is especially suitable for

extending the service life (by up to

15 years) of aesthetically valuable

fair-faced concrete surfaces such as

this particular building.

Structural strengthening

For structural strengthening,

world-renowned Sika CarboDur

Plates were bonded onto the

building as external reinforcement.

Consisting of carbon fibre reinforced

polymer (CFRP) laminates, Sika

CarboDur Plates are exceptionally

strong and durable, non-corrosive

and provide outstanding fatigue

resistance. Nevertheless, they are

lightweight, easily transported and

supplied in numerous combina-

tions of high strength and

modulus of elasticity.

Installation is simple

with minimal prepara-

tion of the plate. Sika

CarboDur Plates are highly

versatile being suitable to

strengthen structures for

load increase, for service

improvements, for changes

in structural systems or

specifications and are

used worldwide for struc-

tural damage caused

by earthquakes.

Sikadur-52 ZA was

used as a high strength

injection resin to fill and seal voids and

cracks in the concrete of 9 Dorp Street. This

two-part, solvent-free, low viscosity injection

liquid not only forms an effective barrier

against water infiltration and corrosion

promoting media, but also structurally bonds

concrete sections together.

Sikadur-31 DW, based on a combination

of epoxy resins and special fillers, was used

as a thixotropic, structural two-part adhesive

and repair mortar.

With easy mixing and application, this

high strength product provides excellent

adhesion to dry or damp concrete sur-

faces. Both Sikadur products harden

without shrinkage.

Sikaflex AT-Facade, used for sealing all

movement and connection joints of this

building, is a one-part, moisture curing

elastic sealant based on silane terminated

polymers and offers excellent workability

and adhesion to both porous and non-

porous substrates.

With movement capability of 25%

and low stress to the substrate, Sikaflex

AT-Facade can be applied between the same

or different substrates. It is solvent-free, sili-

cone-free and provides the highest UV resist-

ance, colour stability and ageing resistance.

After a successful application on 4 Dorp

Street, it was decided to use SikaTop Seal-107

as a waterproofing slurry for protection of

the structural concrete of No 9. This two-part,

polymer modified mortar slurry consists of

a liquid polymer and a cement-based mix

incorporating special admixtures.

With fast and simple mixing, requiring

no water, it is easily applied by brush, thin

trowel or spray method. Ideal for interior

or exterior waterproofing and damp-

proofing, SikaTop Seal-107 protects concrete

against the ingress of contaminants, and is

suitable for moisture control and increasing

the resistivity.

Once again, the City of Cape Town is

assured that Sika’s world-renowned products

have effectively renovated one of its most

distinctive buildings, which will possibly

attain heritage status in the future.

Dorp Street

FACELIFT

Four years after multiple Sika products were used to

successfully renovate 4 Dorp Street, a prominent building

in Cape Town’s CBD, consultants once again relied on the

efficacy of Sika products to enhance and protect another

distinctive building in the same street.