Subject: Re: Geodome construction utilizing balloons?

From: [email-masked] (Rob-L)
Date: 7 Feb 1996 11:00:30 GMT

Mark de Roussier ([email-masked]) wrote:
: >: Has anyone ever heard of constructing a Geodome inflating some kind of
: >: balloon as the skeleton and then covering it with concrete as the
: >: shell.
: >
: >I've heard of it, and seen it demoed, but I'm thinking why not build a 
: >mound of dirt and put rebar/concrete on that?
: >
: 
: Perhaps because the minimum energy shape for a mound of dirt is more
: conical rather than spherical ? i.e. to get the mound of dirt to
: assume the shape you wanted to form, you'd need to shore it up in
: various ways before applying the shell, irrespective of how heavy the
: shell was.

What?  Ever built a sandcastle?  How about a clay pot?  You add water to
the particles, and you have all the shoring you need to make almost any
shape.  It's not a pile of dry granules, or a wet slumpy mixture.  As with
any material, you mustn't over-extend it, but then it only has to hold until
the concrete firms up.  You're shooting the concrete from the base-up,
presumably, so it'll naturally take most of its own loads if you allow it
to cure some before moving up.  Like building an igloo or stone dome, you
don't start at the top - you gradually encircle it upward.

This is ancient technology for buildings.  Positive forms are easy to make.
If you don't want to move as much earth around (it's your berm material too),
use filler.  Put old barrels, or vans, or a bus, or a railroad car under 
the dirt, and roll it out after you dig it free.  Or you can do a 
subsurface structure by -leaving- a positive shape as you dig around it 
>from  above.  Make sure you leave access for digging out the middle.

Air bags are fine, but they are more limited in what they can do easily.
And you generally end up with the insulation -inside- rather than outside 
where it is most effective and desirable.  With concrete inside, you have 
a safer structure from a fire standpoint too.