How Solid is Concrete's Carbon Footprint?

National Science Foundation (May 18, 2009) Concrete may absorb more carbon dioxide than earlier estimates suggested

Concrete absorbs carbon dioxide over time, so its carbon footprint may be smaller than once thought.

Many scientists currently think at least 5 percent of humanity's carbon footprint comes from the concrete industry, both from energy use and the carbon dioxide (CO2) byproduct from the production of cement, one of concrete's principal components.

Yet several studies have shown that small quantities of CO2 later reabsorb into concrete, even decades after it is emplaced, when elements of the material combine with CO2 to form calcite.

A study appearing in the June 2009 Journal of Environmental Engineering suggests that the re-absorption may extend to products beyond calcite, increasing the total CO2 removed from the atmosphere and lowering concrete's overall carbon footprint.

While preliminary, the research by civil and environmental engineering professor Liv Haselbach of Washington State University re-emphasizes findings first observed nearly half a century ago--that carbon-based chemical compounds may form in concrete in addition to the mineral calcite-now in the light of current efforts to stem global warming.

"Even though these chemical species may equate to only five percent of the CO2 byproduct from cement production, when summed globally they become significant," said Haselbach. "Concrete is the most-used building material in the world."

Full article at: http://www.nsf.gov/news/news_summ.jsp?cntn_id=109892