Construction World November 2015

ADMIXTURES

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.

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.

>

When the City of Cape Town decided that 9 Dorp Street, one of the most renowned modernist buildings in the area needed a

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

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

42

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-

CONSTRUCTION WORLD NOVEMBER 2015