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While not sustainable concrete made from fly-ash locks up ongoing and historic waste from coal fired power stations.

We're phasing out our 60 year old coal station given the sheer amount of solar power we now generate in W.Australia - but we still have 60 years of fly ash to deal with.

[1] https://www.abc.net.au/news/2021-09-18/geopolymer-concrete-c...

[2] https://www.mediastatements.wa.gov.au/Pages/McGowan/2022/08/...

[3] https://colliecrete.com.au/

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Yes, fly ash concrete seems more sustainable than concrete without it (provided that the fly ash already exists) in certain applications where its particular properties are beneficial. I seem to recall it having greater durability under compressive loads, so roads can be built that require less frequent repair. In the US, we have enough roads falling apart I think we could use all the fly ash concrete we could possibly make, and we wouldn't have any extra to build substandard, energy-inefficient housing.

Fly ash may be a valuable resource in future. Iirc it's a significant constituent of sulfur-resistant cement, used extensively in concrete sewer pipes.

Isn't fly ash quite high in radioactive material and a source of indoor radon when used in house construction?

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