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Breathtaking architecture made of paper clips

The components - metal pins, rather like large paper clips - may not be much to look at. But what you can do with them is all the more spectacular for that.

It is not even 20 years since Ann Lambrechts developed these pins for the building materials industry, a relatively short time in her sector. Adding them in a certain proportion to wet concrete creates a material with such outstanding properties that it has already come to be used in recent years in unique buildings designed by some of the world's most renowned architects. And inventor Lambrechts has now been nominated for this year's European Inventor Award, to be presented at a ceremony in Budapest on 19 May.

Her innovative work on improving "steel fibre concrete", as the mixture is known, has made buildings and structures possible which, until just a few years ago, could exist only as the product of a creative architect's imagination. These include spectacular multi‑storeys such as the Beijing headquarters of China Central Television (CCTV) and the delicate structures forming the central part of the Oceanogràfic complex in Valencia. Steel fibre concrete is also being used to build the Gotthard Base Tunnel, as it was in the Channel Tunnel linking Great Britain to the Continent.

Breathtaking architecture

CCTV's new headquarters are perhaps one of the most complex buildings ever built: the huge block is reminiscent of a gigantic skyscraper twisted into the shape of an angular loop. Straightened out, this loop would form a tower more than 800 m high. Up to 10 000 people will work in the enormous building, from where they will broadcast 250 TV channels throughout China and the rest of the world. "The project breaks all the boundaries. To begin with, just the sheer dimensions: they go beyond anything any of us, be it our firm or even most other people, have ever done before. After all, it is one of the biggest buildings ever built in the world", says an excited Ole Scheeren, the German architect responsible for its design and construction. "The statics would probably not even have been feasible five or ten years before construction started."

An entirely different impression is made by the undulating biomorphic roofs resembling delicate scallop shells which Spanish-Mexican architect Félix Candela designed for the entrance hall and underwater restaurant of Europe's biggest aquarium, the Oceanogràfic in Valencia. Candela was convinced that strength depended on a material's form and not its mass. Although just 6 cm thick in some places, the sprayed concrete in his roofs is ultra‑strong and stable.

In the Gotthard Base Tunnel, which on completion will be the world's longest railway tunnel, Lambrechts' invention is again being used, this time in the concrete sprayed on to the tunnels to line them quickly, durably and safely after boring. And around 260 000 pre‑fabricated components containing the invention were installed in the Channel tunnels used by the Eurostar trains which run between London and the mainland of Europe.

Improving good material

"Concrete is basically a good material, but it has to be reinforced with steel," explains Lambrechts. "Steel rebars and reinforcing mesh have to be installed before the concrete is poured. Using our method, you simply add the steel fibres to the concrete and then pour the mixture into the desired form." The ends of the fibres are flattened and specially shaped to resemble the letter "Z", which means that they can hook into each other inside the final mixture and so increase the concrete's strength. The tensile strength the fibres provide is about 32% higher than that achieved by previous methods, which enables developers to build faster and more cheaply. "We managed to save more than 10% of the costs involved in traditional methods of building with concrete," sums up Hadyn Davies, the manager who oversaw the Channel Tunnel's construction.

Indeed, since the new technology requires less metal altogether than conventional methods, it has a smaller "ecological footprint". Other properties of the material make it more corrosion-proof and reduce crack formation and so directly guarantee a longer lifespan: no doubt other good reasons why a third of all industrial floors are now manufactured in this way.

Word of the new material's advantages has also reached the EU Commission. As part of its 7th Framework Programme for Research and Technological Development, it is subsidising the TailorCrete project, which aims to initiate a transition from the "rectangular monotony dominating the European landscape today" to "unique concrete structures", without the need for expensive or labour-intensive manual construction processes.

Patent boom

Ann Lambrechts' invention has triggered a mini-boom. Not only is Bekaert, the firm she works for, now the global market leader, but there has also been a sharp increase in other developments, inventions and patent applications in the field of concrete reinforcement, these dealing not only with the materials themselves, but also their processing. From 1970 to 1990, fewer than 10% of patents concerned some kind of metal reinforcement (IPC class E04C 5/01), but by 2007, such patents accounted for 29%, their biggest share so far.

In 2010, Bekaert, which is also the world leader in terms of patents in this area, invested around EUR 79 million (about 2.4% of its sales) in R&D. That represents a 25% increase over 2009, and the firm may well pass the EUR 100 million mark this year. Lambrechts now heads the R&D department and is in no doubt about the value of patents: "By protecting an invention, you also protect your future. If you want to become and stay the market leader, you have to invest continuously in new applications and products."

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