Professor Christian Meyer, chairman of Columbia University's Department of Civil Engineering and Engineering Mechanics, is currently conducting research and analysis on the benefits of using recycled waste materials in producing concrete.

Meyer, who chaired ACI Committee 555, Concrete with Recycled Materials, for six years, points out that the concrete industry already uses waste materials such as slag, fly ash, silica fume, and ground granulated blast furnace slag. Other materials are also being researched, such as recycled carpet fibers and scrap metal. From Meyer's point of view, new sources for recycled material can be found anywhere there are “mountains of stuff nobody wants.”

Professor Meyer spoke about “Concrete and Sustainable Development” during the meeting “Solid States: Changing Time for Concrete,” sponsored by Columbia University in New York City. The Graduate School of Architecture, Planning, and Preservation, and the Department of Civil Engineering and Engineering Mechanics, convened the three-day meeting at which architects, engineers, and professors gathered to discuss “new understandings” of concrete.

Meyer sees potential concrete ingredients in post-consumer waste (glass, tires, plastic, garbage), industrial byproducts (wood, rice husks), and construction waste (recycled concrete, excavated rock). The table notes benefits and challenges of various waste materials that must be explored before being used in concrete.

Developing more sustainable concrete could make a big impact. With more than 10 billion tons of concrete produced each year worldwide, the only other commodity of which we use more is water. “The concrete industry has become a victim of its own success,” Meyer explains. “To produce 10 billion tons of concrete, you need 10 billion tons of materials; therefore, the industry leaves a large environmental footprint, which is a tough challenge to overcome.”

Meyer is doing his part through personal research and by mentoring students who are studying concrete ingredients of the future. Olarn Pornpitaksuk, Bronx High School of Science, is studying phosphogypsum in concrete, which is a byproduct of creating phosphoric acid used in fertilizer, which poses a storage problem in Florida. Theo Pang, a Columbia graduate student, has studied replacing a portion of sand in concrete with mushroom substrate.

Meyer acknowledges economic feasibility may be a barrier to using recycled materials, but he believes it will get easier as virgin materials become scarcer and waste disposal costs increase. “It is not a question of ‘whether,' but ‘when' using recycled materials in construction becomes routine,” he concludes.

For more on Professor Christian Meyer's research, visit or contact him at For a slideshow about the Solid States conference, see