The wonders of modern concrete
Margareta Pagano learns about the hi-tech potential of the world’s oldest man-made building material Look! Concrete!’ Bruno Lafont crashes his fist on the table. ‘You could put 30 tonnes on top of this table and it wouldn’t break. Tougher than steel!’ The table doesn’t look like concrete at all. The top is only a centimetre thick. The surface is painted a Tuscan tone, giving it the feel and look of polished stone. Lafont turns to his desk and bookshelves: ‘They’re also concrete. Aren’t they wonderful?’ These are a more utilitarian beige, but equally handsome. Scattered around the room are more clues to his passions: lumps of gypsum, vital for making cement; more rocks; and an enormous elephant painting, a present from the Prime Minister of Zambia.
Lafont is chief executive of Lafarge, the world’s biggest cement maker. On the corner of a Paris side-street, his suitably concrete 1970s-style headquarters sits oddly in the 16th district, with its chi-chi cafés and markets. It’s early in the day but Lafont is in high spirits: he’s just flown back overnight from opening a new cement works in Morocco; before that he spent a week in India for the opening of the world’s longest conveyor belt, taking limestone into Bangladesh to make cement.
No wonder he’s happy: construction is booming everywhere and concrete is suddenly sexy. Scientists are turning this drab, grey material into bendy, light, hi-tech structures. Even investors get the message: Lafarge’s share price soared 49 per cent over the last year, even before last week’s announcement of record profits for 2006.
Back to Lafont’s table, the clue to concrete’s future. It’s made of Lafarge’s revolutionary new hi-tech material called Ductal. Not only is Ductal lighter and tougher than conventional concrete but it moves too making it perfect for earthquake zones. Five times tougher than normal concrete, it’s also many times stronger than steel. Mixing fibres made from steel or polymers into the concrete makes it stronger, eliminates the need for reinforcing steel bars, and allows it to bend without breaking as ordinary concrete does — a property called ductility.
Architects and engineers are crazy about this material. They can design structures such as roof canopies and bridges to be more delicate yet longer-lasting. A pedestrian bridge has just been built in Korea in concrete that is only a few centimetres thick. A light rail transit station in Calgary, Alberta, has been made entirely of Ductal to cope with huge weights of snow and fierce winds.
There are environmental advantages, too. Less cement, and therefore less energy, is needed for any given structure. ‘After water, concrete is the product most consumed by humans on earth,’ Lafont expounds. The US alone uses 500 million tonnes of the stuff every year — and the cement industry is responsible for some 7 per cent of the world’s carbon dioxide emissions. Enormous amounts of fossil fuels are needed to heat limestone and clay to the high temperatures needed to create cement — the paste which binds concrete.
Making concrete itself is simple — the recipe is about 70 per cent sand, gravel or crushed stone, 15 to 20 per cent water, plus the cement. But to make a tonne of Portland cement, the most common sort, about a tonne of carbon dioxide is released into the atmosphere.
Lafarge is not alone in pushing concrete to new frontiers. Rivals in Germany are working on translucent cements in which tiny transparent optical fibres the thickness of hair create a material which literally allows sunlight to pass through a structure. Colourful concrete floor tiles made with recycled glass are another product of this technology. The Italian cement giant Italcementi has developed concretes which absorb pollutants from the air by using the white pigment titanium dioxide. Originally used to keep concrete white and bright, it was found by accident to have properties which clean the air by breaking down noxious pollutants such as sulphur dioxide.
Lafarge’s own eco-credentials are as green as can be. One of its project is Hypergreen, a joint venture with one of France’s top architects, Jacques Ferrier, to build tall, sustainable buildings which aim to be environmentally friendly in every aspect. Hypergreen’s buildings use solar power and wind turbines built into the fabric of the structure, which also captures rainfall for recycling into the building’s sanitation system.
Lafarge has set up a research chair for the ‘Science of Materials for Sustainable Construction’ with two of France’s leading engineering schools. A state-of-the-art research centre opens near Lyons later this year, so that Lafarge’s 500 technical and engineering staff can experiment with structures such as bridges to scale.
New concretes have also been developed to meet predicted shortages in the labour market. Laying a 60 cubic metre concreteslab floor in an office building usually takes eight people about eight hours to do. But a Lafarge product called Agilia now allows the concrete to consolidate under its own weight and doesn’t need masons with vibrating machines, so the same floor can be made by two people in a couple of hours.
What Lafont can’t avoid is the inevitable devastation to the landscape caused by his company’s quarries. But to make amends, Lafarge works closely with the World Wildlife Fund and governments to reduce environmental impact. In Kenya a crocodile zoo has been made out of a former quarry.
Lafont has only been in the hot seat for a year, but he’s been preparing for the job for a lifetime. Now 50, he has been with Lafarge since 1983 when he joined from the Haute Études Commerciale, France’s leading business school. ‘You could say I’ve had a long time to think about what I’d like to do,’ he laughs. It’s just as well that making cement is a long-term game in which it is expensive for rivals to catch up — although Holcim of Switzerland and Cemex of Mexico are not far behind.
Lafont refers to his cement plants affectionately as ‘cathedrals’: once commissioned, they last for at least 50 years. Lafarge churned out 123 million tonnes of the grey glue in 2005 and is planning to add another 40 million tonnes of capacity to meet soaring demand over the next five years. It was one of the pioneers when cement was first manufactured in France in the 1820s and its concrete helped make much of Wall Street and the Suez Canal. Lafont plans to keep it at the cutting edge of construction technology.
‘We’ve been using concrete since the Romans started mixing lime with pozzolana, the volcanic ash of Vesuvius. No one yet has come up with a substitute. Instead we’re pushing the boundaries, developing new materials and products.’ The fist comes down again. ‘Just like my table.’
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