Project description

The fifty story high Carlton Centre, was officially opened in 1973 at a total cost of over ZAR 88 million (approximately CHF 8 million). Forty years later, it still stands proud as the tallest building on the African continent. 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, an emergency restoration project was initiated. Several products from Sika’s Concrete Repair and Protection System were specified, given their durability and cost effectiveness.

Project requirements

Due to the sheer height of the Carlton Centre, which stands at 223 meters, as well as unpredictable winds and atmospheric conditions surrounding it, the highly experienced SA Rope Access Company was awarded the hazardous task of applying Sika’s high performance products.

Sika Solution

Once preparations, which included chipping away the contaminated and spalling concrete as well as splicing the old rusted rebar, were completed, repair work commenced. SikaTop Armatec 110 EpoCem (35 kits), a cement-based, epoxy-modified, three-component, anti-corrosion coating and bonding agent was used in conjunction with SikaRep LW (200 bags), a one-component, non-sag, cement-based, multi-purpose patching and repair mortar.

 

Waterproof corrosion inhibitor
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, and provides a high degree of mechanical strength. Containing corrosion inhibitors, it is ideally suited for repairs to concrete in which corrosion of the reinforcing steel has occurred.

 

Structural concrete repair
SikaRep LW, used for cosmetic or structural 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 adhesion, is also shrinkage compensated. SikaRep LW is permeable to water vapor and offers a high resistance to freeze/thaw cycling.

 

Adhesive and repair mortar
Cracks in the concrete were repaired with Sikadur-31 CF Normal (20 kits), a moisture-tolerant, thixotropic, structural two-part adhesive and repair mortar based on a combination 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 vapor.

 

Steel protection
Sika FerroGard-903+ (1000 liters), the fourth product in the repair and protection system, was applied to treat the entire top ream of the Carlton Centre. This treated area, located on the fiftieth floor, covers the 360° Observation Deck, known as the Top of Africa.

Sika FerroGard-903+, a surface-applied, mixed corrosion inhibitor, is based on organic compounds designed to penetrate concrete to form a protective monomolecular 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 of corrosion while also decreasing the rate of corrosion, which thereby increases service and maintenance life cycles by up to fifteen years. It is especially suitable for extending the life of aesthetically valuable fair-faced concrete such as on historical structures, as in this case, the Carlton Centre.

Complying with 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 vapor diffusion properties of the concrete. Providing long-term protection and durability, this product can be used where no other repair/prevention options are viable. Contractors were able to complete the project within the specified time schedule.

project participants

  • Owner/ Client: Transnet Properties
  • Architect: SMEC Vela VKE
  • Engineers: Willem van Ede
  • Contractor: SA Rope Access- Fabian Gentz