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Success in Sustainable Development

12/1/2007

Global warming is an all too apparent fact of life-one that is no longer up for scientific debate. Largely the result of the rising world population, the generation of increasing quantities of greenhouse gases (CO₂ being the most prominent) leaves the world facing the bleak possibility of continually rising temperatures and other major climate changes that will affect every human on this planet. Slowing population growth will slow the rate of increase in CO2 production, but there is far more that can be done to mitigate the negative effects on the climate.

A key weapon in our arsenal for reducing global warming is sustainable development in construction. The goal is to minimize the impact of the built environment through a reduction in CO₂ production and energy use-including building with renewable, recycled, and waste materials. The idea is to share the planet and its resources, not just with those alive today, but with those who will follow.

In the U.S., the U.S. Green Building Council (USGBC) and the Green Building Initiative (GBI) have been leading the way to develop guidelines for construction that minimize our CO₂ "footprint." In addition to emissions, energy use, and materials, the guidelines also address land use, water use, and indoor air quality. Based on the criteria in the guidelines, buildings can be certified under the USGBC Leadership in Energy and Environmental Design (LEED) and GBI Green Globes programs. For example, using fly ash or blast furnace slag as partial cement replacements can contribute to earning credits for a project because they are waste materials, as can the use of renewable resources, such as timber, and recycled materials, including reused structural steel and concrete.

Today, sustainable development is often driven by local politics (requiring green practices or certification) and economic incentives, such as tax credits and construction subsidies. The political and economic facts were brought home to members of the concrete industry last March at the Concrete Summit on Sustainable Development, held in Washington, DC, and sponsored by ACI's Strategic Development Council (SDC). The summit has been followed by two other SDC workshops, one in September and one in November, in San Diego and then St. Louis, with the specific goal of developing a roadmap for the concrete industry to actively pursue sustainable development. I am pleased to report that the roadmap is coming together quite nicely.

Some other industries are far ahead of the concrete industry in developing criteria for sustainable development, but the results of some of their efforts provide an excellent example of errors that the concrete industry should work hard to avoid. For example, a building (not concrete) that had achieved platinum (top rank) LEED certification is undergoing significant deterioration less than 2 years after it was constructed. The problem: selecting and using materials in a manner not appropriate for the building's environment.

The key lesson is that sustainability means more than using renewable, recycled, or waste materials-it also means choosing materials and construction procedures to produce structures that will remain serviceable for the full design life with minimum requirements for maintenance. And because of the political and economic considerations, it means that the criteria used by groups such as USGBC and GBI need to recognize practices that are known to achieve this goal.

Fly ash provides a good example. When fly ash is used as a cement replacement, concrete must be cured longer than concrete made with 100% portland cement to achieve the same strength and freeze-thaw resistance. Thus, fly ash may not be a good choice in construction requiring a short curing period, or even the same curing period as used for concrete made without fly ash. Taking the example a step further, increasing the curing period for structures made with any combination of cementitious materials by even a week has the potential to add years to service life through decreased permeability and reduced cracking. Under current rating system criteria, the use of fly ash is recognized, but adequate or increased curing is not. Clearly, we have work to do.

As the world population, expected to grow by 75 million this year alone, approaches 6-3/4 billion people, it would be wise for all of us to minimize our individual impact, as well as the impact of our industry on global climate change. To succeed, we must pursue sustainable development using all of the knowledge available and by recognizing and making wise choices in both the selection and application of concrete materials.

David Darwin
American Concrete Institute
daved@ku.edu

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