Molding vermicrete

[fxpose]

Can vermicrete be applied in globs of layers over several days and molded or carved into shape over the dome? This will be applied over 3" of blanket at the top of the dome so I'm not really after its insulating qualities. What would be a good workable vermiculite to portland ratio for this purpose? Stucco will be applied over this to finish.

George

[gdest]

Re: Molding vermicrete

Yes you can, go to this site and it will give you all the informtion you need:
http://www.perlite.org/perlite_info/...e_concrete.pdf

[fxpose]

Re: Molding vermicrete

Thanks!! Exactly the info I needed.

George

[Neil2]

Re: Molding vermicrete

A 12:1 mix will work. If you keep it on the "dry" side it can be moulded quite well.

[fxpose]

Re: Molding vermicrete

I cannot find vermiculite but my local Home Depot sells perlite. Also, a nearby masonry supply house sells perlite as well, and considerably cheaper than Home Depot.
The Home Depot perlite (made by Therm-o-Rock) are pea sized. Is this the right kind to use as I read elsewhere here that I had to use perlite that had already been heat treated and 'popped' to larger sizes? How do you distinguish them or is there any difference? I have not yet seen the perlite from the masonry supplier.

George

[gdest]

Re: Molding vermicrete

Perlite in its raw form looks a lot like sand. The popped perlite will be white. However I have never seen perlite that is pea sized, this sounds to me more like vermiculite.

Gary

[fxpose]

Re: Molding vermicrete

Thanks Gary. These were white and about pea sized. One bag had a small hole in one corner and this is what I saw. Perhaps that was not indicative of what was in the rest of the 2 cu/ft bag. How large or what's the ideal size to look for?

George

[gdest]

Re: Molding vermicrete

George

WOW that's going to be a tough one to answer. But let me try. I had a subcontractor run some tests for the perlite I was going use on one of my jobs and here are the results:
US Sieve Size 16 - 10% retained
US Sieve Size 20 - 5-25% retained
US Sieve Size 30 -50 15 -30% retained

Now as I provide that information, basicly perlite (cracked) is not sold by size. Cracked perlite will be VERY light and should look a lot like sugar and have about the same size of regular sugar.
If the bag says perlite I would trust it. However it brings to mind me trying to buy fire clay and everyone who said they sold fire clay actually sold me mortar.

Gary

[fxpose]

Re: Molding vermicrete

I made a quick stop at Home Depot again this morning and kind of poked further into the bag to find that they are actually smaller than pea sized. They basically all looked like tiny broken pieces of styrofoam, light, white, and fluffy. I'm not sure if this is the right stuff to use. I imagined they would be a lot larger in size.

This is what they have:

[jota112233]

Re: Molding vermicrete

Hi George - I've got a pic of vermiculite. This is what it looks like this side of the pond.

This is V4, which is the biggest.



Regards

Jon
Cardiff

[Neil2]

Re: Molding vermicrete

All perlite sold at nurseries will be "popped" or expanded. What use is it an any other form ?

I tried to see which of the boxes on the bag in your photo were checked off. Perlite often comes in "fine". "medium" and "course". You want the "coarse" grade.

[fxpose]

Re: Molding vermicrete

I checked with the local masonry supplier and they only carried them in fine form so I went ahead and picked up the medium aggregate from Home Depot. I'm not using it for insulation, but just for forming and molding. I think this will work just fine.

Thanks,
George

[fxpose]

Re: Molding vermicrete

Can I add lime to the perlite/cement mix? Would that make molding easier, as far as making the mixture sticky? I just happen to have a lot of lime left from doing the homebrew.

George

[Tscarborough]

Re: Molding vermicrete

Sure you can, but I wouldn't go past 1:1 with portland if you are planning on troweling a finish coat over it.

[fxpose]

Re: Molding vermicrete

Perfect. I'll do that.

Thanks,
George