Concrete is probably used more widely than any other substance except water, yet it remain

s largely unappreciated. “Some people view the 20th century as the atomic age, the space age, the computer age — but an argument can be made that it was the concrete age,” says cement specialist Hendrik Van Oss. “It’s a miracle material.” Indeed, more than a ton of concrete is produced each year for every man, woman and child on Earth. Yet concrete is generally ignored outside the engineering world, a victim of its own ubiquity and the industry’s conservative pace of development. Now, thanks to environmental pressures and entrepreneurial innovation, a new generation of concretes is emerging. This high-tech assortment of concrete confections promises to be stronger, lighter, and more environmentally friendly than ever before.

Concrete is also a climate-change villain. It is made by mixing water with an aggregate, such as sand or gravel, and cement. Cement is usually made by heating limestone and clay to over 2,500 degrees F. The resulting chemical reaction, along with fuel burned to heat the kiln, produces between 7% and 10% of global carbon-dioxide emissions. “When we have to repeatedly regenerate these materials because they’re not durable, we release more emissions,” says Victor Li who has created a concrete suffused by synthetic fibers that make it stronger, more durable, and able to bend like a metal. Li’s creation does not require reinforcement, a property shared by other concretes that use chemical additives. Using less water makes concrete stronger, but until the development of plasticizers, it also made concrete sticky, dry, and hard to handle, says Christian Meyer, a civil engineering professor at Columbia University.

Making stronger concretes, says Li, allows less to be used, reducing waste and giving architects more freedom. “You can have such futuristic designs if you don’t have to put rebar in there, or structural beams,” says Van Oss. A more directly “green” c6nerete has been developed by the Australian company TecEeo. They add magnesium to their cement, forming a porous concrete that actually scrubs carbon dioxide from the air.

While experts agree that these new concrete will someday be widely used, the timetable is uncertain. Concrete companies are responsive to environmental concerns and are always looking to stretch the utility of their product, but the construction industry is slow to change. “When you start monkeying around with materials, the governing bodies, the building departments, are very cautious before they let you use an unproven material,” Meyer says. In the next few decades, says Van Oss, building codes will change, opening the way for innovative materials. But while new concretes may be stronger and more durable, they are also more expensive — and whether the tendency of developers and the public to focus on short-term rather than long-term costs will also change is another matter.

By saying “it was the concrete age”(Line 3, Para. 1), Van Oss means that

A．the traditional building material concrete is the only man-made miracle.

B．concrete is indispensable in the development of modern construction industry.

C．compared with other inventions, concrete is more practical and useful.

D．concrete, as a building material, can be mixed with any other materials.