greening concrete

[amor de cosmos]

Experts Propose Research Priorities for Making Concrete ‘Greener’

The challenge of making concrete greener—reducing its sizable carbon footprint without compromising performance—is just like the world's most ubiquitous manufactured material—hard!

But, according to a new report* from the National Institute of Standards and Technology (NIST), the potential engineering performance, energy-efficiency and environmental benefits make it a challenge worth tackling.

Many factors determine the overall energy and environmental impact of concrete. However, reducing the amount of portland cement, which reacts with water to bind all the sand, stone and the other constituents of concrete as it hardens, provides the biggest opportunity. Depending on the particular concrete formulation that is used, portland cement accounts for approximately one-quarter of the total mass, and it is the product of a very energy-intensive process.

Nearly a kilogram of carbon dioxide, the main greenhouse gas, is produced for each kilogram of concrete that is constructed. Portland cement manufacturing accounts for more than 5 percent of U.S. industrial carbon-dioxide emissions, according to the report. In addition, the U.S. cement industry consumes 400 gigajoules of energy annually. That's equivalent to the energy required to power more than 3 million homes each year.



Consensus high-priority research topics identified by the experts include:

• Developing tools and metrics for quantifying the advantages and disadvantages of using different materials in concrete.
• Developing and validating computer models that can predict the performance of green concrete mixtures, both during construction and over the long term.
• Improving test methods for characterizing materials such as fly ash, glasses, and minerals and other portland cement substitutes to determine whether they will perform as required.
• Developing a more complete understanding of the water-driven chemical interactions that occur as industrial byproduct materials and other components are incorporated into concrete.

http://www.nist.gov/public_affairs/t...x.cfm#concrete