Most concrete produced is from portland cement, and it consumes more energy and pollutes more than any other industry including steel and plastics.  It contributes 5-8% of all greenhouse gases just by itself, and prduction is growing at about 5% annually.

Fly ash is a waste product of a coal combustion plant.  It is the non-combustible portion of coal that used to be released into the air before through the smoke stack before the government put more strict regulations on what can be release into the atmosphere.  The particles themselves are spherical and smooth and more fine than cement particles. read more »