When did you last specify cement? I expect the answer is never. There are certain products in architecture that are just seen as commodities. It is not that concrete is not interesting - many of the architects designing with exposed concrete care passionately about the quality and nature of the finish, and hence about the nature of the aggregate, the formwork and the way it is made - but cement? Well, that's just cement, isn't it?
Talk, however, to Lafarge Cement and it bridles at this concept. Not surprisingly, selling commodities is a thankless task since all the consumer cares about is the price and the effectiveness of delivery. For contractors, the company has developed methods of bagging and delivery that make their lives more convenient, establishing difference in that way. But for the world of architecture it has to take a different approach, developing specialist materials in which getting the cement right is as crucial as the other materials, and hence turning the cement into a specification product.
One of these materials is Agilia, a suite of self-placing concretes that offer high-quality fi nishes as well as certain on-site advantages.
Far more radical is Ductal, described as 'the fi rst ultra-high-strength concrete'. Containing reinforcing fi bres and without the need for reinforcing steel, this material can be used to form fantastically slim, smooth and strong elements. First pioneered in the Far East on a footbridge, its use has now spread to the US, Canada and France - and with the right project could come here soon.
In Canada it has been used to form very slim shells on the roof of Calgary Railway Station. In the US the highways authorities are considering its use for road bridges - as well as the light weight, there is the elimination of reinforcement that brings with it potential problems of corrosion. Ductal nearly achieved a much higher profile in the US, since it was to play a key role in Daniel Libeskind's design for the Freedom Tower at Ground Zero before the attrition to which his initial scheme was subject in the name of commercial viability. Structural engineer Guy Nordenson explained at a seminar at Princeton University that the enclosure for the radio antennae was originally to be formed from Ductal elements - before that part of the design was chopped off.
In France, Bandol-based architect Rudy Ricciotti is to use Ductal to form the filigree screen to his Museum of the Marine for Marseille, a project won in competition against a host of big international names.
Ductal creates a beautifully smooth surface, but is a specialist product, not a cure-all.
It is, weight for weight, extremely expensive.
It needs to be produced off-site, in controlled precasting conditions, and there are still questions over the effi cacy of jointing elements. And its slenderness, of course, negates the advantages of thermal mass that are so often touted as one of the reasons for designing in concrete.
But as an addition to the ways in which the material can be used, it is both fascinating and challenging. An exhibition at the National Museum of Building, sponsored by Lafarge and called 'Liquid Stone', shows both the best of imaginative concrete architecture and technological inventions such as 'transparent concrete' that has caught the public's imagination. At the Princeton symposium, speakers explored the myriad possibilities of the material. From the more technical view, engineer Franz Ulm, an associate professor at MIT (Massachusetts Insititute of Technology), spoke of the benefi ts that he foresees nanotechnology bringing in the future, while practitioners described methods of achieving the effects they want today.
Ulm reminded his audience of the unique nature of concrete - that there is no other solid material in use today formed from mixing a powder and some bits with water to form a solid. It is rather like making a cake without needing to cook it. But for the bestquality cakes, you would not pick most of your ingredients and the recipe with care, and then use any old fl our. So why any old cement? If we are to embrace the most sophisticated of concrete technology it will be true that, in those instances at least, we will have to stop treating cement as just a commodity.