ASPIRE is a quarterly magazine published by PCI in cooperation with the associations of the National Concrete Bridge Council. The editorial content focuses on the latest technology and key issues in the Concrete Bridge Industry.
Issue link: http://www.aspiremagazinebyengineers.com/i/306888
16 | ASPIRE , Fall 2008 P E R S P E C T I V E ENVIRONMENTAL Benefts of Concrete Bridges Every day, sustainability becomes an all-encompassing concept that applies to every aspect of the design and construction of all structures; concrete bridges are no exception. Sustainability addresses the "triple bottom line"—environment, community, and economy. By balancing the three, the needs of present and future generations can be met. This article focuses on the effects concrete bridges may have on the environment—are they good to and good for the environment? Concrete is a Sustainable Material The primary raw material used to create cement is limestone, which is abundant. Concrete is made even more sustainable by the use of fly ash, which is recycled waste material from coal-fired power plants. Fly ash has been used this way for many years, and most projects in the United States today include fly ash in the concrete. Other recycled cementitious materials include blast furnace slag and silica fume. Reinforcing steel and prestressing strands are also recyclable materials. The portland cement industry is a leader in protecting the environment and promoting sustainability. The industry has reduced emissions by 33% since 1975 and plans to voluntarily reduce CO 2 emissions to 10% below the 1990 baseline. Concrete uses recycled materials, abundant materials, and environmentally conscious manufacturing processes while providing the bridges that our communities need and depend on for transportation, commerce, and quality of life. Concrete is Recyclable Producing only as much concrete as is needed for a project reduces waste. And when a concrete bridge has reached the end of its useful life, the concrete can be recycled by crushing it and using it as fill for roads. In addition to reducing waste in landfills, this approach reduces the need to mine and process new materials and limits pollution involved in transporting material to sites. An example of this type of materials management can be found in the article on page 20 about Oregon's bridge program. As another example, after the Arthur Ravenel Jr. Bridge was constructed in Charleston, S.C., more than 248,000 tons of concrete were salvaged from demolition of the two structures it replaced. The material was used to create 82 acres of reef habitat. ASPIRE_fall08.indb 16 9/15/08 4:01:03 PM