Citi-Con’s concrete knowledge was successfully deployed to remove efflorescence from the Amazon head office’s landmark development in Cape Town.
Working closely with Paragon Architects, the architects, WBHO, the principal contractor, and StonCor Africa, a leading supplier of asset repair and maintenance systems, Citi-Con designed a system that would remove the efflorescence effectively.
Project details
The concrete repair specialist successfully employed its extensive experience to solve the abnormal discolouring of exposed concrete on the new 38 000m² Amazon head office in Precinct 2 of the R4-billion River Club mixed-used development.
Repair operations coincided with the various specialist trades, which were completing the final aspects of the build. Therefore, the work had to be done in an extremely short timeframe to avoid delaying the opening of the building to its tenant.
Citi-Con finalised the project, which should have taken three months, in only two months.
Concrete staining
About 8 000m² of exposed concrete was significantly stained. This included the full length of the entire concrete beam around the perimeter of the building. The repair method was tested on various sample areas and proven to be effective, practical and feasible.
This involved first thoroughly cleaning the substrate to remove all dirt and loose particles. Efflorescence on the concrete beam around the perimeter was so severe that it had to be removed by grinding off a thin layer of concrete. Other areas were washed by hand with a weak-acid solution cleaner.
A total of 8 500m² of glass windows had to be masked before repair work commenced, to avoid permanently staining them.
Cleaning
As per StonCor’s instructions, the surface areas were flooded with the solution, ensuring a rundown on the masonry of between 150mm and 200mm.
To avoid a high spread rate that would greatly reduce Pro-Struct 670’s effectiveness as a water repellent, a litre was used for every 2m² to 4m². This was dependent on the irregularities of the substrate surface.
Sealing
Before the concrete could be sealed, all the windows had to be masked to avoid permanently staining them. This was an extensive undertaking that entailed covering 8 500m² of glass within the vicinity of the various working areas.
The concrete was then sealed with StonCor’s Pro-Struct 670 – a modified siloxane solubilised in aliphatic hydrocarbon for deep penetration in concrete substrates. This system is very effective in resisting water and salts that are normally encountered in natural-weathering conditions.
Two coats of the product were applied to a dry surface with a low-pressure spray. The second was placed after about six hours and then allowed to cure over seven days.
Impeccable health and safety practices were implemented on this project.
Site challenges
Environmental
Various areas of the building had to be prepared simultaneously so that the programme could continue when the Citi-Con team was unable to work between the two towers due to very high wind speeds.
Considering Cape Town’s “micro-climate” that presented new and unforeseen safety risks, Citi-Con had to adapt its programme regularly. This was done while working closely with WBHO to ensure a minimal impact on the final aspects of the build.
Access
Accessing the various work faces was a significant challenge. Initially, Citi-Con intended undertaking the entire project with rope access. This was considered a quicker, more cost-effective and safer method of working at height, doing away with the need to erect scaffolding.
However, the building’s many overhangs obstructed the rope technicians. They were, therefore, equipped with window-suction cups to pull themselves closer to the working areas. While effective, it was a slow and tedious process.
Citi-Con therefore also deployed suspended cable systems and mobile scaffolding towers that could be easily moved around the perimeter of the building to the worksite. Adjusting them to the site elevations, the mobile scaffold towers provided safe and quick access to the fourth-floor level.
Health and safety
Accessing the various work faces was a significant challenge for Citi-Con’s team of certified rope-access technicians.
In total, 13 Citi-Con team members worked on this project, including the company’s certified rope-access technicians. By bolstering the team and incorporating various innovative work-at-height methods into the programme, the company was able to finalise the scope of work a few days before the “builders’ holiday”, saving the client both construction time and costs.
Impeccable health and safety practices were implemented on this project. Integrated health and safety specialist, KBC Health and Safety, was employed to assess and manage occupational health and safety risks on behalf of Citi-Con.
Throughout the project, Citi-Con’s own robust occupational health and safety practices were in line with these of WBHO. The principal contractors’ own “zero-harm” policy extends beyond its own operations to all its project stakeholders.
Preferred provider
As an approved StonCor applicator, Citi-Con has extensive experience working with Pro-Struct 670. Thus, the company can guarantee its workmanship for the maximum available term.
Citi-Con is considered a preferred provider of building revamp services. Together with a guarantee of high-quality workmanship performed by professionals, it provides an efficient, practical, cost-effective and safe method of repairing new and existing concrete.
Issue: Removal and repair of significant concrete staining in a short time period.
Solution: Citi-Con performed a comprehensive concrete repair, in collaboration with other stakeholders, to deliver a fast-tracked, successful project.
For more information, contact Citi-Con:
Tel: 087 148 2023
Email: info@citicon.co.za
Website: https://www.citicon.co.za/