Concrete Igloo or Vault

For years I have been thinking of how to build a mold or a couple of different molds   that I could poor concrete into  where I could make one or two pieces a day  for a few months  to get enough parts to be able to stack together like an IGLOO for a dome or as a VAULT .    I have seen Igloos made from Styrofoam parts   but a concrete igloo would be much more durable.   Sometimes I think of a Soccer Ball for parts of a sphere but there must be more ways to build a dome.... Such as Orange slices  of an orange fruit that has been cut in half.
Anyone else ever think of this ?   I would like a way for the pieces to if not  lock together , at least a ledge that helps reinforce the next  row.   You would never want to be in  a concrete igloo when it collapses!   How to make it strong ?    We know how the Romans used stones to build arches and bridges etc.

Neat idea, I love building methods that can be done incrementally.
To minimize the number of molds needed and the side of the pieces, maybe try this kind of dome:

https://www.domerama.com/calculators/trapezium/

This is like the orange slices.
To figure the dimensions of a block rather than a flat panel, calculate an inner and an outer dome and the distance between the two.

I think styrofoam blocks skinned in netting and plastered with cement could be a good option.

Concrete made with Styrofoam could also be good:
https://permies.com/t/271989/Good-yt-video-increase-knowledge

Adobe blocks are free, but they do requires attention to detail that I myself don't think I could mister
Cast soilcrete blocks might be the best option in terms of materials required vs skill level.

Scott, where are you located, it helps understand your needs a bit.
Concrete blocks can be cast, you need he skills of a stone mason or strong mathematics.
As William suggested adobe is straight forward, the material id free but the end product is not
it takes a lot to create adobe bricks.
Creating the dome based on a circle is covered in much literature but essentially you start with a foundation, a centre pole and a bit of string.
The bricks are laid around the pole using the string as a guide.
Other techniques are used to create the actual dome shape you want.

I can’t find the video now, but I watched one a long time ago about a farmer that built an under ground dome house just like building a cob bread oven. He built a big mound of dirt, covered it with old tarps, then built a rebar frame and poured stiff concrete. When set, he dig out the dirt and used it to bury the dome.

William Bronson wrote:Neat idea, I love building methods that can be done incrementally.
To minimize the number of molds needed and the size of the pieces, maybe try this kind of dome:

https://www.domerama.com/calculators/trapezium/

This is like the orange slices.
To figure the dimensions of a block rather than a flat panel, calculate an inner and an outer dome and the distance between the two.

I think styrofoam blocks skinned in netting and plastered with cement could be a good option.

I really think the trapezium idea could work..  There are a total of 64 pieces and the use of four different mold shapes.    I am afraid even if the molds were made with two pieces  resulting in each piece shaped like a bowl
to hollow out the pieces and make them lighter,  I still wonder if they would be too heavy if made with pure concrete.  If Styrofoam concrete was used then would they still be strong enough ?   Wonder what it would cost to convince a styrofoam mfgr to build molds and produce pure styrofoam blocks that could be glued together.?
and then the styrofoam  dome could be covered with net and plaster of some type for weather protection.
If the eskimos can do it with ice we ought to be able to do it with something else that wont melt  

Okay, crazy idea to make the concrete a bit lighter: What if you use charcoal as part of the aggregate, instead of sand? I've been playing around a little bit with making cob with char instead of sand, and it seems decently strong. Though I suppose if you're going to cover the dome with soil or similar, "decently strong" might not be quite enough...

Aerated concrete I think will be afer than replacing sand with charcoal.Concrete gets its strength because of the interaction between the sand and the aggregate,
assisted by the coating of cement covering everything.
Since charcoal has a lower shear strength than sand, it may not actually work at all.

Scott Perkins wrote:.
If the eskimos can do it with ice we ought to be able to do it with something else that wont melt  

https://theconversation.com/styrofoam-igloos-a-1950s-cure-for-the-inuit-housing-crisis-160073

Now that I've studied the photo and read all the background,  I am  more amazed than ever at the fact that the styrofoam Igloo was NOT built with standard size blocks but instead each block was carved  for a perfect fit just like the packed snow made igloos.  It took me a few months to notice on the far right side of the foam igloo  that the igloo at the top several layers were actually a continuous  swirl  round and round
to the top Just like the packed snow Igloos.  With a lot of geometry I feel certain that molds could be made to use the blocks right out of the mold and fit together somewhat like LEGOS.   If the styrofoam blocks were going to be glued together,  I wonder what the best adhesive would be because you probably need a 55 gal barrel of it and that would cost tens of thousands of dollars.