Use fly ash in concrete

Fly ashFine particulates consisting primarily of silica, alumina, and iron that are collected from flue gases during coal combustion. Flyash is employed as a substitute for some of the portland cement used in the making of concrete, producing a denser, stronger, and slower-setting material while eliminating a portion of the energy-intensive cement required. More info can replace some of the Portland cement in a concrete mix
Manufacturing Portland cement uses a lot of energy and produces about 6% of the world’s carbon dioxide emissions. Replacing the 12% Portland cement mix in concrete with 15% to 25% Type C or Type F fly ash are fairly common, and mixes up to 60% are sometimes used. Contact your local Department of Transportation for advice about mixtures they've tested; this will help when talking to your building inspector and concrete contractor.

Green points:

LEEDLeadership in Energy and Environmental Design. LEED for Homes is the residential green building program from the United States Green Building Council (USGBC). While this program is primarily designed for and applicable to new home projects, major gut rehabs can qualify. -H 1/2 point available under MR2.2 (Materials & Resources) for fly ash or slag as replacement for 30% or more of Portland cement in foundation

NGBSNational Green Building Standard Based on the NAHB Model Green Home Building Guidelines and passed through ANSI. This standard can be applied to both new homes, remodeling projects, and additions. /ICC-700 Up to 4 pts. for recycled-content—fly ash or slag substitution for Portland cement in concrete (604.1).

Learn more in the Green Building Encyclopedia:

FOUNDATION CHOICES—Scroll to 'Deeper Shades of Green'

FURTHER RESOURCES

Making Better Concrete, Bruce King, Chelsea Green Publishing, 2006

Toolbase.org: Fly Ash Concrete