Easily taken for granted as the stuff for sidewalks, roads, power plants and parking garages, concrete is also, however, a favored material of many talented architects and engineers as shown in a new exhibition in Washington. As the title of the exhibition implies, concrete is a paradoxal material. It is synonymous with hardness, yet fluid when first mixed. It is by definition a hybrid, made from cement, water, sand and mineral aggregates such as gravel or crushed stone, but is commonly regarded as a distinct, homogenous substance. The exhibition shows about 30 selected projects by innovative architects divided by several categories revealing the different aspects of the material: Structure, Surface and Sculptural Form. The "Structure" section includes projects such as the Torre Agbar in Barcelona, designed by French architect Jean Nouvel - a skyscraper whose skin is conceived as a built version of a pixilated digital image, with an irregular grid of concrete panels forming unexpected geometrical shapes and framing views in surprising ways. The "Surface" section will feature a complex in Japan by Tadao Ando, in which the signature design gesture is a large, shallow pool lined with an impeccably ordered array of seashells embedded in concrete. Yet another project, a Technical School Library in Eberswalde, Germany, by the Swiss firm of Herzog & de Meuron, takes advantage of an astonishing new technique in which photographic images are engraved directly onto concrete panels, creating a surface that is simultaneously building skin and artist's canvas. The skin becomes a kind of surreal three-dimensional photographic album, repeating each image 66 times around the full circumfence of the building. The final curatorial category, "Sculptural Form," expresses most dramatically the great potential of concrete in cutting-edge design. The new Auditorio de Tenerife, in the Canary Islands, by architect/engineer/sculptor Santiago Calatrava has been designed to become the very symbol of the Canary islands, just as the Sidney opera house did in Australia. The astonishing new concert hall in Tenerife is as much a work of sculpture as of architecture. The giant soaring wave of reinforced concrete serves no functional purpose, but establishes the monumental scale. Portions of the concrete forms are covered with white ceramic tiles that recall the work of Antoni Gaudi. The exhibition concludes with a section called "The Future of Concrete," which examines concrete technologies and hybrids that are just now on the horizon. For example, self-reinforcing concrete, which so far has been used in only a small number of structures of significant size, will facilitate the creation of long-span concrete shells of incredible thinness. Perhaps most amazing of all is the prospect of translucent concrete, now under development by several researchers in the United States and Europe. Imagine walls that offer the security, strength, and fire protection of concrete block, but that also transmit light. The prospects for innovative new works of architecture using such a material stretch the mind. New architecture in concrete, June 19, 2004 – January 23, 2005 at the National Building Museum, Washington Source: National Building Museum, Washington