Lafarge’s ArteviaTM : the beautiful solution for Chevron headquarters
Chevron South Africa wanted a landmark sustainable design for its new 9500 m² headquarters in Century City, Cape Town. The winning architectural design proposed a white concrete building, but Chevron was initially sceptical that the local construction industry could successfully build a major structure in white concrete that would meet its rigorous quality requirements. Lafarge South Africa’s Readymix Cape Town team convinced them that its innovative ArteviaTM decorative concrete was the solution for achieving a beautiful, durable concrete finish. Completed in 2014 at a cost of over R200 million, today the superb landmark building is a testament to the team’s confidence.
Lafarge South Africa is the local presence of the international LafargeHolcim Group, a world leader in building materials. The Group is committed to creating innovative materials and building solutions that contribute to more durable, sustainable and beautiful environments for all. Aiming to meet the challenges of the fast-moving construction industry and to better serve architectural creativity, innovation is at the forefront of the Group’s major investment in research and development.
Lafarge ArteviaTM is one of a range of decorative concretes available in an extensive choice of colours and textures, providing almost unlimited scope for architectural expression. It 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, minimising the effect on appearance if the concrete surface is chipped or damaged in any way.
The project involved what was believed to be the largest volume of white concrete ever used in the Western Cape. For the Readymix team, the operational challenge was to produce a consistent mix with raw materials – white cement and white pigment – that they hadn’t used routinely before. Basing the mix on white cement demanded absolute cleanliness throughout the production, delivery and placement process, in close collaboration with the main contractor to enable them to achieve a high-class consistent finish.
“As the majority of the concrete was placed by crane, an area that tested our technical skills at the beginning of the project was maintaining concrete workability for the contractor. This challenge was resolved by our technical team and the admixture supplier,” says Lafarge South Africa’s Regional Technical Manager, Craig Mills. “We were fortunate in having backup from a team of concrete experts based at the Lafarge Centre of Research in France, on challenging projects. The reactivity of the white cement created a problem and in one instance, a particular cantilever had to be removed due to retardation. However, our Technical Department investigated the problem and put preventative measures in place to mitigate any reoccurrence.”
The unique high-class white concrete project had to be carefully planned and meticulously controlled. 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.
As there could be no risk of contamination, the extent of the challenges that had to be addressed had been hard to envisage: it involved the contractor purchasing new equipment purely for white concrete use; the contractor’s 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.
But extreme cleanliness up to concrete placement 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. Rusting of the rebars was a concern and a sealant was used to close plastic shrinkage cracks to minimise the risk of rusting. 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.
“This project was a good example of how it is possible for various stakeholders to work closely together to achieve an exceptional result,” comments Pieter de Bod, Lafarge’s Key Account Manager for Cape Town. “We were fortunate to have Chevron as an owner/client, who insisted on a high quality, sustainable building as the overriding priority.”
With the strong support from Lafarge South Africa’s product and technical solutions, the contractor tackled all the challenges and delivered the best white concrete off-shutter result they had seen, and an outcome that exceeded the client’s expectations.
“This outstanding building stands as a proud statement that in partnership with LafargeHolcim’s technical resources, the local building industry has the construction skills to create a world-class result,” concludes Mills.
Lafarge Artevia™ was the solution for the marble-like white concrete of the landmark Chevron building. (Pic: courtesy of Louis Karol Architects & Interiors)
The superb Chevron building gleams like travertine marble. (Pic: courtesy of Louis Karol Architects & Interiors)