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Concrete + 30% Fly Ash

October 14, 2009

We are using 30% Fly Ash in our concrete for foundation.  Fly Ash is a fine, glass-like powder recovered from coal-fired electric power generation plants.  Millions of tons of fly ash are created annually in the US from power plants and are usually dumped in landfills.  Using fly ash in concrete mix is considered green because it takes the waste what would typically end up in landfill and put them back in use.  Reducing the amount of cement in the concrete is also considered green as the production of cement is a energy-intensive process.  Use of a ton of fly-ash to subtitue for a ton of cement can save enough energy to power an average american house for 24 days and reduce CO2 emission equal to 2 month’s use of automobile.  Fly ash concrete also requires less water in the mix.

See the following link for more information for the use of fly ash in concrete.

Use of fly ash content improves strength, workability and pumping of the concrete.  The curing time will take longer, but the concrete will have a higher ultimate strength. 

Use of 30% fly ash is not a common practice.  Many concrete suppliers do not supply this on a regular basis and may not have the strength test for such mix.  We got our concrete from Glacier Northwest (now a part of CalPortland).

Our concrete mix for the foundation is as followed:

• Sand                            1230 lb
• aggregate                  1850 lb
• Type I-II cement     470 lbs
• Fly ash                          200 lbs
• Water                             265 lbs

Load total: 35Water/cement ratio: 0.396

Filed under: green features