aircrete vs. ferrocement

  • Little Dragon Tamer

    Here's a conversation about making aircrete in cold temperatures.

  • Little Dragon Tamer

    Aircrete is not waterproof - it does wick water to a certain degree. It has been demonstrated to float for years, which has created some confusion about being waterproof. It is mentioned on the site as being "waterproof, fireproof, termite proof, rot proof" which is to say that water doesn't hurt it, as compared to say drywall and particle board. The statement could be misleading for some, but I think it's not intended to be.

    Perhaps a waterproofing agent could be added to aircrete. Might be worth an experiment.

    I don't think that water absorbed into aircrete would cause freeze cracking. This is suggested by the fact that it floats for years - it continues to contain enough air to remain flexible against freezing. These videos furhter support the notion: Freezing Wet Aircrete Blocks and Aircrete Patio Spring Assessment

  • Little Dragon Tamer

    Randy and Kathy Johnson have had great success with their pure aircrete patio, but overall I think it's best to top an aircrete walking surface with a 1/2 to 1 inch coat of concrete. I did one recently using coarse gravel in the top coat. If I were to do it again I would use fine gravel or sand only so that I could keep the thickness down to 1/2" or so.

  • Another issue... it seems that thermal insulation is poor with brick concrete.

  • Little Dragon Tamer

    @claudettn said:

    there is always the risk that the aircrete blocks are not done the right way and you have no way to test their quality...

    ASTM (pka American Society for Testing and Materials) has fully addressed aircrete, referring to it as Cellular Concrete.

  • Major Contributor

    You are right in what you are saying. You should try to build according to your code if you are building in a code requirement area, which is virtually most of the USA now. Regardless what other people might try to imply, testing is neither difficult or expensive. You can test the strenght of your aircrete or regular concrete and is around maybe 100 dollars for sampling, which includes about 5 cylinder samples. When I did mine, they were around 75 per 5 cylinder sample, and that included the technician going to the site and gathering the sample before the pour, and doing a test ON the concrete that was going to be poured to predict if it would possibly pass the PSI of concrete ordered. You could collect your own samples, as the cylinders are readily available, and then bring them to any engineering testing firm and that would save you money. Aircrete, or what they want to call aircrete in this page is in reality cellular concrete. This have been discussed before in this forum. Real aircrete expansion is by a chemical ( using aluminum powders) mean and then you need an autoclave to hot cure it for hours, which give ultimate tensile strenght. Domegaia concrete is not commercial aircrete but cellular concrete. Its strenght in compression is good, but its tensile strenght not so much, so you would need something to give that strenght. It could be rebar , metal lath or even better basalt rebar, which is expensive but is mineral and have higher tensile strenght than metal. You could also consider a thin layer of magnesium concrete, which is much stronger than any other concrete and can be laid out thin, but it is expensive, and then over that layer put basalt rebar and then aircrete. Many ways to do it, but the cellular concrete by itself is not too strong by itself for a building that needs coding. Minimum compression strengh of a concrete building in most codes is 1500 psi for walls and 2500 for a concrete rebar ceiling. PSI in the hundreds for a building is not much different than mortered foam blocks. The ideal would be a middle point, using the magnesium concrete and basalt rebar to hold the tensile strengh, and the celular concrete to give insulation. There is also basalt fiber that is sold in mats or just the fibers. That could also be added to celular concrete for even more insulation. Even another solution would be to buy a concrete inflatable dome cheap in alibaba from a chinese suppliers. They use them for fairs and displays. Then use that filled with air as a holding structure, and using regular concrete by hand in a thin layer, or maybe shotcrete or gunite and rebar. This will also give you a stronger shell that can be worked over with celular concrete. Then at the end good coating of sealing paint to make it weatherproof. Whichever way you choose good luck.

  • @HandyDan How many bags of cement did you use for the 24' dome?

  • Major Contributor

    @Jaay 250 Bags due to the thickness of the builds.

  • @Zander

    Hi Zander,

    It's been a while since I worked with concrete in a modern fast track environment but I do remember we used to test our concrete with every delivery.

    Most frequently using a slump gauge, see -

    That page also has moulds for casting test blocks. Which can then be tested to destruction in various ways. E.g. crushing to test compressibility, I've also seen people keep them in sealed containers of water for several months, and then cut them to see how far it has penetrated.

    I dare say there are more tests you can do ...

  • @HandyDan In regards to using air Crete for a floor, what reinforcing would you use and how thick would you make it. My current application would be a base for patio pavers but I’m also interested in using it for the floor elsewhere.

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