When Chevron South Africa, a leading refiner and marketer of petroleum products, looked for a landmark sustainable design for its new headquarters in Century City, Cape Town in 2011, it invited architects to compete for the design contract. Winners, Louis Karol Architects & Interiors, proposed a ‘naked' white concrete building but the client was initially sceptical that the local construction industry could successfully build a major structure in white concrete. As the concrete solution, Lafarge South Africa proposed its innovative Artevia™ decorative concrete.
"Lafarge was totally confident of being able to provide solutions for building in white concrete, no matter what challenges might arise. This was a key factor in Chevron accepting our design concept," says architect Robert Silke, design director at Louis Karol. "The white concept was not purely an aesthetic one; it was also an elegant solution to the client's sustainable development requirement. Most buildings are built twice: the main structure goes up and then a decision is made on the expensive cladding to be used, be it aluminium, stone, glass or plaster and paint. Raw grey shutter concrete can be considered too ‘brutal' and is often painted over within six months."
Lafarge South Africa is the local presence of the international Lafarge Group, a world leader in building materials. The Group is committed to creating innovative materials and solutions that contribute to Building better cities that are more durable and beautiful environments for all. With the world's leading building materials research facility, innovation is at the forefront of the Group's major investment in research and development. It aims to meet the challenges of the fast-moving construction industry and to better serve architectural creativity.
ArteviaTM decorative concrete is a high quality structural concrete combining durability and low maintenance with a high standard of aesthetic finish. The product is produced with an integral UV stable colour pigment. The homogeneous mix minimises the effect on appearance if the concrete surface is chipped or damaged in any way. The innovative ArteviaTM range is available in an extensive range of colours and textures, providing almost unlimited scope for architectural expression.
Main contractor, Stefanutti Stocks Building Western Cape, started construction of the
9 500 m² Chevron head office in 2012, and completed the project in March 2014 at a cost of over R200 million. The building has met the client's requirement to achieve a 5 Star Green Star SA Office Design v1 rating and is on track to have a 5 Star As Built rating confirmed. The striking building is a high-end, world-class structure in off-shutter concrete with infill glass panels between the white concrete columns. It is divided into four quadrants by two major expansion joints and consists of three floors of offices with basement parking, as well as recreation areas, a canteen and laboratories on the ground floor, surrounding an open-air courtyard.
"We believe the Chevron project involved the largest volume of white concrete ever used in the Western Cape," commented Johann van der Merwe, Contracts Manager for Stefanutti Stocks. "The extent of the challenges that had to be addressed was hard to envisage but Lafarge Cape Town Readymix worked closely with us as a team to ensure a successful outcome. Lafarge is very solutions focused and are able to call on the unparalleled technical resources of the international Lafarge Group."
"An area that tested the technical skills of the team at the beginning of the project was maintaining concrete workability for the contractor, which was resolved by our technical team and the admixture supplier," said Lafarge South Africa's Craig Mills, Regional Technical Manager. "We are fortunate in having back up from a team of concrete experts based at the Lafarge Centre of Research in France, should we require assistance with challenging projects such as this one. The problem was due to the reactivity of the white cement. In one instance, a particular cantilever had to be removed due to retardation. Technical Department investigated the problem and, identifying the root cause, put preventative measures in place to mitigate any reoccurrence."
"As a unique high-class white concrete project, cleanliness and quality management throughout the production, supply and placement of our white Lafarge ArteviaTM concrete
had to be carefully planned and meticulously controlled," comments Lafarge South Africa's Sivuyile Ngobozana, National Product Manager - Readymix. At the Lafarge batch plant, special white cement was used and the white colour of the mix enhanced further with white pigments. The plant team had to use a dedicated truck loading hopper for the white ArteviaTM mix and carefully wash all conveyor belts before loading the Lafarge truck mixers, which had been washed and inspected thoroughly. Sand colour variation was a continual concern and this, combined with the reactivity of the white cement, required a Lafarge technical representative to monitor the concrete for all the pours.
"We had to purchase new equipment purely for white concrete use," commented Van der Merwe. "There could be no risk of contamination. Ironically, the special shutters that we used were made from an extremely smooth specific resin board called Black Resin Board. Our trucks could not have been used for standard grey concrete previously. All placing equipment had to be set aside purely for white concrete use, including two banana buckets and even the compacting vibrators."
Cleanliness wasn't the only factor in ensuring the white finish was of the required high standard; shutter release oil was a critical area to avoid staining and, after extensive trials,
a water-based product was selected. Similarly, rusting of the rebars was a concern and a sealant was used to close plastic shrinkage cracks to minimise the risk of rusting. This was particularly relevant because shrinkage of the white mix proved to be abnormally high. To minimise cracking, the tops of the columns were covered with wet hessian immediately after casting and, as soon as the formwork was stripped, the columns were wrapped in plastic wrap and then Perspex. The Perspex worked well to prevent damage that would not have been possible to repair.
"At the end of all these challenges, we managed to deliver a finished product that did not
just meet but exceeded the client's expectations," added Stefanutti Stocks' Van der Merwe. "The finish is outstanding, by far the best white concrete off-shutter result we have seen in our experience. We could not have achieved this without the strong support from Lafarge South Africa's product and technical solutions."
Standing back to appreciate the overall effect, the superb Chevron building gleams like travertine marble. While initially it has been expensive to create, the monolithic external structure will only require cleaning every seven or eight years. "We are overwhelmed by the outcome," enthuses architect, Silke. "The building looks beautiful and demonstrates that in partnership with Lafarge's technical resources, the local building industry has the construction skills to create a world-class result. We were fortunate to have Chevron as a client, who insisted on a high quality, sustainable project as the overriding priority."
In South Africa, the company manufactures and supplies cement, aggregates, readymixed concrete, gypsum plasterboard and interior building fittings. It focuses on providing solutions to help the sustainable development of better cities that benefit the country's people. Through having a strong presence in all of its business lines, it is in a unique position to contribute to urban construction, while also helping to build better cities, rural towns and villages.
Lafarge South Africa also demonstrates active concern for the conservation of the country's wildlife heritage and is a major supporter of the world's first dedicated baby rhino orphanage in Limpopo Province.
note to editor
As a world leader in building materials, Lafarge employs 64,000 people in 62 countries, and posted sales of €15.2 billion in 2013. As a top-ranking player in Cement, Aggregates and Concrete, it contributes to the construction of cities around the world, through its innovative solutions providing them with more housing and making them more compact, more durable, more beautiful, and better connected. With the world's leading building materials research facility, Lafarge places innovation at the heart of its priorities in order to contribute to more sustainable construction and to better serve architectural creativity.
Additional information is available on the website at www.lafarge.co.za
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