A New York Times article from the March 30, 2009, issue describes current efforts to modify the composition of concrete keeping environmental concerns in mind. The article focuses on the new St. Anthony Falls Bridge in Minneapolis (see below).
The author of the article also has a related blog posting on the Green Inc. blog.
Concrete has been the focus of past MRS symposia as well as the MRS Bulletin including the May 2004 issue on Construction Materials: From Innovation to Conservation.
Credit: Bill Alkofer for The New York Times
Soaring above the Mississippi River just east of downtown Minneapolis is one remarkable concrete job. There on Interstate 35W, the St. Anthony Falls Bridge carries 10 lanes of traffic on box girders borne by massive arching piers, which are supported, in turn, by footings and deep pilings. The bridge, built to replace one that collapsed in 2007, killing 13 people, is constructed almost entirely of concrete embedded with steel reinforcing bars, or rebar. But it is hardly a monolithic structure: the components are made from different concrete mixes, the recipes tweaked, as a chef would, for specific strength and durability requirements and to reduce the impact on the environment. One mix, incorporated in wavy sculptures at both ends of the bridge, is designed to stay gleaming white by scrubbing stain-causing pollutants from the air. It is a prime example of major changes in concrete production and use — changes that make use of basic research and are grounded, in part, in the need to reduce concrete’s carbon footprint.
All that concrete may seem the same. And the basic product did remain relatively unchanged since the invention of Portland cement in the early 1800s. (The ancient Romans made concrete, too, but from volcanic ash.) Producers have always tinkered with the mix to find the right proportions of concrete’s basic ingredients, but the recipe never varied much. Now the experimentation is more elaborate, designed to tailor the concrete to the need. Increasingly, that need includes the environment.
Dr. Gopal Rao
Web Science Editor
Editor, Meeting Scene
Materials Research Society (MRS)