In 2010 Group 5 was awarded a contract by the City of Cape Town to renovate 4 Dorp Street, a prominent building situated in the heart of the city. BBI Consulting Engineers was contracted to manage all civil engineering aspects of the project.
Jakupa Architects and CS Studio Architects unequivocally specified no less than eighteen of Sika’s advanced technology products for the renovations, which included concrete repairs, joint sealing and protective coating. Commencing in October 2010, it was estimated that the project, which involved a surface area of 28000m² and a total of 3037 windows, would take approximately one year for completion. Sika’s first encounter with 4 Dorp Street had been four years previously in 2007, when the project was originally initiated and Sika was the preferred supplier.
To date, window renovations have called for the supply of 3,812 x 600ml sausages of Sikaflex -11FC, a one part, polyurethane-based, moisture-curing, elastic joint sealer and multipurpose adhesive. Providing very good ageing and weather resistance, this versatile product is suitable for indoor and outdoor applications. Another high performance product used on the windows was Sikaflex AT-Façade (3,529 x 600ml sausages). Based on silane-terminated polymers, it is especially suitable for joint sealing on movement and connection joints and offers the highest UV resistance resulting in excellent weatherability.
Preparation of the windows necessitated the use of Sika Cleaner-205 (19 litres), an alcohol solution containing a bond-activating substance for non-porous substrates and Sika Primer-3N (4 units), a one component, epoxy-polyurethane solvent-based primer for use on porous substrates.
For protection of the glass as well as worker safety, all windows were insulated with reusable timber boards. Due to noise created by the city centre, acoustic tests were conducted to determine noise pollution levels penetrating the building. As a result all windows were insulated and bonded.
Concrete renovations to the building have been achieved using Sika’s world-renowned repair mortars; Sika MonoTop-610 (513 kits), a bonding slurry and primer containing active corrosion inhibitors; Sika MonoTop-615 HB (2452 kits), a high build, repair and reprofiling mortar containing silica fume, designed for repairing thick layer concrete, especially in overhead and vertical applications; Sika MonoTop-612 (180 kits), a fibre-reinforced mortar which can be wet sprayed or applied by hand. The above-mentioned mortars are all cementitious, one- component, polymer-modified products.
Further easy-to-use, high performance Sika products supplied to date, are Sika Rep LW (392 units), a one component, non-sag, cement based multi-purpose patching and repair mortar suitable for vertical or overhead applications on exterior or interior surfaces, and Sikadur-31 CF Normal (one kit), a moisture tolerant, thixotropic, two-part adhesive and repair mortar. Based on a combination of epoxy resins and special fillers, this product is ideally suited for corners, edges, holes and void filling, and joint and crack sealing. Another excellent void and crack sealer supplied is Sikadur-52 ZA (3 kits), a two-part, solvent-free, low viscosity injection liquid, based on high strength epoxy resins. It not only forms an effective barrier against water infiltration, but also structurally bonds concrete sections together.
After repairs on the first floor of the building were completed the contractor realised there was a discrepancy in concrete repair volumes and that, compared to the original quote, 80% supplementary materials were needed. Emergency funds were requested and the estimated completion time for this project was extended to June 2012, a further eight months.
To date, various waterproofing and bonding agents have been supplied; Sika’s Cemflex (12 x 5 litres), an acrylic based emulsion; SikaLatex (5 x 5 litres), a high quality, synthetic polymer emulsion; SikaTop-Armatec 110 EpoCem (605 x 1.75 litre packs) a cement-based, epoxy-modified, three-component, anti-corrosion agent providing excellent adhesion and a high degree of mechanical strength, and SikaTop Seal-107 ZA (1291 kits), a two-part, polymer-modified, waterproofing and damp-proofing cementitious slurry.
A problem was encountered during surface preparations when water jet pressure, which was originally quoted, was found to be insufficient to create adequate open-pore surfaces for maximum adhesion. The contractors resorted to using grinding machines that were fitted with vacuums to extract excess dust created during the process. Once suitably prepared, the surfaces were coated with two applications (1mm thick) of SikaTop Seal-107 ZA.
Grouting was finished using SikaGrout-212 (665 bags), a high performance, easy to use, cementitious, fluid expanding grout, providing rapid strength development and high final strengths. Sikacrete-214 (110 bags), a one-component, free flowing, high strength micro-concrete with a maximum aggregate size of 9mm, has been used for casting sections where volumes required are too large for conventional grouts and too small and inaccessible for normal concreting procedures.
For high performance adhesions, the product of choice was Sika AnchorFix-2 (48 units), an epoxy acrylate-based anchoring adhesive that is solvent- and styrene-free and can be used for all grades of concrete, reinforcing steel, threaded rods, bolts, solid masonry and steel. It is fast-curing, provides a high load capacity, is non-sag even on overhead surfaces, and application is possible using the standard gun method.
The main challenge encountered during this project was delamination of the external plaster, which not only posed public safety problems, but also caused significant noise pollution. This resulted in labour working night shifts to complete the delamination process, while repairs were carried out during the day.
Upon completion of the facelift/renovations to 4 Dorp Street, the City of Cape Town will feel justly proud of one of its city centre buildings and will be secure in the knowledge that Sika’s internationally approved products have featured in every facet of the renovations.