fly ash

Hi - hope you are doing well

Your program on PBS twice mentioned the use of fly ash in your concrete.
I think I understand the purpose of fly ash in concrete but can you please
tell me the concrete mix formula you prefer? I usually think of these things
in parts per cubic yard. One formula provided to me elsewhere is - 6 bag,
6 slump, and 6 fly ash, remainder in sand and preferred aggregate. My
preferred aggregate is 1/2 to 1 inch flint rock.
But i became interested in your formula after one of your guests mentioned
fly ash for a second time.

Thank you
Wayne

Fly ash is the fine residue powder byproduct from coal-fired electric generating plants. Since the burning of coal provides up to 85% of our electricity (depending on where you live), a great deal of this powder is produced. Some 63 million tons of fly ash were produced in 2002, resulting in 63 tons of mercury byproduct.

Currently, the fly ash is released into the air, buried in a landfill or illegally dumped into our oceans. fly ash contains approximately 1 part per million of mercury (NOTE: The maximum level of mercury in drinking water permitted by the EPA is 2 parts per billion.) The mercury seeps into our groundwater and contaminates our fish. Humans eat the fish, and the mercury accumulates in our bodies.

Mercury has been linked to numerous health problems, including autism in newborns, endocrine disruption and cardiovascular disease. Since 1990, there has been a 10-fold increase in the incidence of autism. One can quickly see a need for an alternate use of this fly ash.

(NOTE: It only takes 1/70th of a teaspoon of mercury to contaminate a 20 acre body of water and make all fish within it toxic to humans. This is about the amount of mercury in a typical medical thermometer.)

Concrete is a mixture of sand, water, stone, and Portland Cement. The cement is the key ingredient in concrete, comprising about 12% of the mix weight, acting as the binding agent that holds sand and other aggregates together in a hard, stone-like mass.

Energy consumption is the biggest environmental concern with Portland Cement, requiring a great deal of energy to mine out of the Earth, grind up, heat in a kiln and process into the final product. Cement production is one of the most energy intensive of all industrial manufacturing processes. One can also see a need to find an alternative for cement.

Kevin,

I very much like your show, and last night saw the episode in which you poured a foundation using "fly ash" to substitute for cement. While this may have certain environmental advantages, some fly ash is slightly radioactive, depending on the original coal. This may result in a foundation with issues similar to the radon accumulation issue in homes with basements. Especially in an energy efficient home, where the air circulation level may be low, I would at least look into what the radon emitting characteristics of the fly ash will be.

Best regards,
Cas Milner

Yikes! I learn something new every day. Someone else alerted me to the radioactive possibility in fly ash. I actually had a Geiger counter brought in to test our concrete. There was no evidence of radioactivity. Radon is different from Radioactivity. It emanates naturally from the ground, particularly in certain regions, especially (but not only) regions with granitic soils. However, not all granitic regions are prone to high emissions of radon. Depending on how houses are built and ventilated, radon may accumulate in basements and dwellings. Many methods can reduce radon in homes. I would like any scientific information you or others have about radioactivity in fly ash.

Sincerely,

Kevin

Kevin,

Is that pot or fly ash that you used in the concrete? Years ago I heard that about a 30 percent mixture waterproofed the concrete. What are the advantages of using ash? Why is it a green choice?

Thanks,

Gary

Gary,

This document will tell you everything you need to know about fly ash concrete.

Kevin