Foamcrete domes cast between two airforms, any trials yet?

Design
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Have there been any development work with foamcrete?

My understanding is that foamcrete uses less material than concrete, since the aggregate has been replaced with soap bubbles. Maybe it takes the same or more portland cement.

To make a form for a foamcrete dome, use an ecoshell for the outer wall. It probably would not work to just make an entire smaller airform inside, then fill the area in between from the top. Maybe an airform with 1-2 foot tall donut rings, where you inflate just the bottom ring, then pour that, before inflating the next ring. That way you have access to the full circumference in 1-2 foot lifts. This makes the inner airform and inflation support much more complex, and probably 3x the material, but hopefully it is completely reusable. Possibly the lower ring could be inflated with water instead of air, to help anchor it to the floor.

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We have not. There are a few reasons why we’re not super excited about it.

  1. We tried out a TON of alternative insulation methods, and none of them worked very well. Interestingly enough, the data showed that a good reflective coating was more effective at controlling heat than any other foam concrete could. The lime wash, done the right way, was by far the best with the Texas heat.
  2. We build FEMA rated buildings. We need the high strength concrete to do that. Foamcrete doesn’t offer that (today).
  3. We also have to do what’s economically feasible, as we are out building domes every day. There are some alternatives, but they are time consuming and often complicated to put into real production.

That said, I hope I am not discouraging you or others from experimenting more with this stuff. The tests we did were not fruitful, but they were very fun, and we are using those buildings today! So, it can be done.

Now let’s discuss dual membrane domes. I have actually spent some time on this, and I think I have it figured out finally. I haven’t tested it yet, but its more complex than people think.

  1. There is no way water will hold this airform down. Trust me. I have inflated a few domes before. You are going to need a concrete footing, and it will need to be substantial enough to hold down the airform.
  2. The tests we’ve done are very minimal, but I hope to do more someday. The next one I do will target a full pour in one shot, and it will probably not be a “foam” mix, but it could have some ceramic beads in it to keep it light.
  3. The Airform will be the most technical part. I may keep that piece close to the chest for now, but this conversation is making me want to get out there and try it again…..

Thoughts?

1 Like
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Excuse me if I am incorrect in assuming that foamcrete and aircrete are the same things. But, there’s an article Aerated concrete vs. thin-shell concrete | Monolithic.org

4

No Yes, I am fully aware of that old article from monolithic dome founder Dave.

I just have a number of issues with the assumptions of use, and argument from authority, along with the lack of nuance, or math.

1 Dave invented the MD spray foam shotcrete method, so he is biased that direction.

2 Dave says elsewhere that R-value “doesn’t matter” as much as air-sealing, which removes the R value comparison, and there are EcoShells uninsulated at all for some markets, which might better be served by foamcrete.

3 A main market for MD is for US certified shelters which require some X inches of Y-psi concrete; sure, foamcrete is not for that application, but there are other applications.

4 The “whipped air” argument doesn’t mention that air is a cheap and universally available resource, that replaces more costly and less available aggregate.

5 the compressive strength argument has no math to support it. Domegaia foamcrete domes exist, so it works for some applications. Dome strength is not the rocket equation, where the weight of more fuel needs more fuel to lift it. (My hand wave vs his).

Mike says they have done some tests, and that lime wash external coating is better than any foamcrete could be. I’m glad there is data, but I’d like to see the details.

My hypothesis is that a foamcrete dome might work better, cheaper, easier than an uninsulated Ecoshell, for Peter, at high altitudes in the Indian mountains; or similar places, particularly in remote places with high cost of aggregate transport.

The engineering problem is how to make it less labor intensive than foamcrete blocks like Domegaia method, using reusable air forms that MD has so much experience.

A foamcrete machine is much cheaper and needs less power and chemicals than spray urethane and shotcrete. I’ve been to the some building workshop (and shot someone in the face when I lost control of the shotcrete gun.)

Maybe foamcrete MD are just a cool idea with no commercial applications at the intersection of cost/complexity vs useful function in specific cases; or maybe there is.

I’m probably blind to the idea the concrete needs to be coated for permanent use in the weather.

1 Like
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I see, and thank you for explaining. I’m just an old retired technician. I responded to multiple large scale disasters, so my primary concern is with monolithic domes abilities to withstand Nature’s wrath. I see their energy efficiency as an added bonus. The dome shape should be adequate for wind speed resistance. But, for wind blown debris resistance I would want high strength galvanized steel reinforced concrete. I would also add Helix steel micro rebar to supplement and not reduce the traditional rebar reinforcement. :innocent:

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The real problem as I see it is that if a dome is being built, then there must be some serious use for it. If that, then there will be serious money being allocated for the construction and therefore serious financing involved.

Financing. It always involves the financing and all the justifications for the financing.

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I agree that financing is a major hurdle. In developed countries, it is often tied to insurance requirements and for-profit business models that can sustain the development costs, anticipating a market in developed countries with building codes. (AI polished)

What is left? Some combinations of:
A- 3rd world or/and communists countries
B- rural no code, maybe in tropical climates
C- YouTubers, and “influencers”
D- NGO non-profit 501c.3
E- engineering school projects, thesis
F- “big foamcrete” equipment & suppliers
G- Eagle Scouts, etc
H- philanthropic, “true believers”

Maybe G makes a camp shelter;
Then H&F make grants for G to do E then D, for use in AB; free advertising from C

I’m not suited for C, so I should give up this idea until I decide to be H for grandchild G, who will show that E is untenable, and stops.

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Well, you’ve got your ABCs down pat. :smiley: I’ve been down some similar life events and could never make a decision on a dome build where one of the possible consequences was losing my investment in the future home site. Most other real estate ventures are easier to get financed, etc.

The future marketing and investment strategies for a dome home have to be considered seriously.