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-   -   Shaping vermiculite concrete dome (http://www.fornobravo.com/forum/f7/shaping-vermiculite-concrete-dome-18133.html)

clg763 07-27-2012 11:54 AM

Shaping vermiculite concrete dome
 
I would like to hear some ideas for the easiest way to shape a vermiculite concrete dome over my modular oven. I have blanket insulation and want to finish it with a stucco dome, from my reading, the simplest way to do this would be to shape vermiculite concrete over the top. I have seen several different people make rebar armatures for their oven and place the concrete on the that, I have also heard that all you need is the vermiculite concrete to shape the dome. I am worried about maintaining a decent looking dome shape with this approach.

I know many have done concrete vermiculite domes but I am having trouble finding good builds and photos from my searching.

Gulf 07-27-2012 04:09 PM

Re: Shaping vermiculite concrete dome
 
Most just shape the vcrete by eye and do great work. Some have used templates. I can't swear that it is easier to use a template but here are some pics of mine.
http://i438.photobucket.com/albums/q.../Oven/0087.jpg
http://i438.photobucket.com/albums/q...Oven/00911.jpg
http://i438.photobucket.com/albums/q...Oven/00520.jpg

Les 07-27-2012 04:55 PM

Re: Shaping vermiculite concrete dome
 
Gulf,

I wished I would have thought of that. I did mine with rebar and wire and it was a bitch. Yours is incredibly symetrical...

Neil2 07-27-2012 05:11 PM

Re: Shaping vermiculite concrete dome
 
The chicken wire seems to be to hold the blanket in place. If you are using vermacrete alone as insulation for the dome you can skip the chicken wire.

Les 07-27-2012 05:30 PM

Re: Shaping vermiculite concrete dome
 
Quote:

Originally Posted by Neil2 (Post 135674)
The chicken wire seems to be to hold the blanket in place.

Neil,

I used the wire over the rebar to form the dome. I slopped vermiculite / portland in between the wire and the blanket.

Gulf 07-27-2012 05:54 PM

Re: Shaping vermiculite concrete dome
 
Quote:

Originally Posted by Neil2 (Post 135674)
The chicken wire seems to be to hold the blanket in place. If you are using vermacrete as insulation for the dome you can skip the chicken wire.

I probably, could have saved that step (and $) for the render :). I am planning to install a layer of stucco wire in the render over the vcrete. I will be laying 1/2 concrete splits over this to finish.

Gulf 07-27-2012 06:59 PM

Re: Shaping vermiculite concrete dome
 
Quote:

Originally Posted by Les (Post 135672)
Gulf,

I wished I would have thought of that. I did mine with rebar and wire and it was a bitch. Yours is incredibly symetrical...

Thanks Les,
In all of my experince with building (born as an endentured servant into a construction family :)), I have been taught to rely on measurements, levels, strings, speed poles, templates (the list goes on). I did not trust my "young eyes" so I definately don't trust this old pair that I have now :D.

david s 07-28-2012 12:23 AM

Re: Shaping vermiculite concrete dome
 
I place the vermicrete with my hands, one handful at a time, starting from the bottom of the dome work all the way around with one hand on the outside and then one on top to create a ledge for the next row. I press and hold for about two seconds and it stays really well, but you need to get the mix just right. If you have water sitting in the bottom of your mixing bucket then you've added slightly too much water. When you've placed the vermicrete over the whole dome you can tap the surface with the face of a trowel lightly to get a perfect hemisphere.

clg763 07-28-2012 06:10 PM

Re: Shaping vermiculite concrete dome
 
Ok, I have begun putting the vermiculite concrete on the dome using a 10:1 ratio, I am having a very hard time getting the cement to set up though.

I started off with a 3:1 ratio of water to cement for the slurry, then poured this over my vermiculite and mixed this by hand. The mixture did not have the feel of good concrete, it was still very crumbly despite all the moisture and nothing I could do seemed to help the texture. I just sort of set a course of a few inches around the dome but the mixture was a fairly loose pack and I don't feel good about it. Now, almost two hours later, the mixture has not set at all. I have never seen concrete do this, what am I doing wrong?

david s 07-28-2012 08:20 PM

Re: Shaping vermiculite concrete dome
 
I find mixing 10 parts vermiculite to 1 part cement (by volume) dry, then adding 3 parts water and mixing it with my hands in a large (20 litre) bucket works pretty well. Replacing the vermiculite portion with 50% vermiculite and 50% perlite improves the workability of the mix.


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