#1  
Old 04-23-2009, 01:09 AM
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Default vermiculate vs cement

Hi all, my son and i just dug about a inch of vermiculate out of the top slab. It had been a week and still soft. I guess i want a form base to work on. I am now thinking of just using concrete blend and mixxing some vermiculate in with it.

I am going to lay anther layer of chicken wire down then my mix of 50 concrete blend to about 40 of the vermiculate and a good amount of cement.

Will this be ok my oven will only be used now and again just to cook a couple of pizzas or a roast.

Thanks for any feed back

P.S i am worried about the slab cracking if it does can it just be filled in so it does not look to bad

cheers all
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Old 04-23-2009, 03:52 AM
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Default Re: vermiculate vs cement

The mix you are planning seems entirely wrong. It won't have any strength and it won't have much insulating value. Or maybe I'm misunderstanding you, maybe with some more explanation and a picture or two we could help more.

I've gone back and read your two previous posts, and I still don't understand. Please explain to us:

Did you start with a support slab? Is it reinforced? How thick is it? What concrete mix did you use for it?

Your vermiculite concrete layer: How thick is it? What proportions did you use to make it? How did you mix it? Did you use vermiculite from the garden supply, or silicone treated stuff made for domestic insulation?

Again, when we know more, we can help more.
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Old 04-23-2009, 03:57 AM
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Arrow Re: vermiculate vs cement

Hi

I have looked back through your posts and not much detail on what or how you did it.
The type of vermiculite, your mixing ratio and method of mixing is critical to the insulation layer success.
I followed Nissanneill's build and it worked out very well. He has his oven build at
http://www.fornobravo.com/forum/f8/n...-1-a-2005.html (Neill's Pompeii #1)
and see the second posting which he explains well the vermiculite material, mixing and included pictures.
He has since given the forum away but his advice and help still remains.

Rastys
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Old 04-23-2009, 04:43 AM
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Default Re: vermiculate vs cement

Quote:
Originally Posted by dmun View Post
silicone treated stuff made for domestic insulation?
BTW, I used the silicone treated stuff and was able to get a very nice product for use under the hearth and over the dome. Low ratio of cement to vermiculite and the finished product floated. I still need to stucco the outside but the material seems to be holding up well after a year.

Jim

Yeah, it was tough to mix but I used the water cement slurry method with good success
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Old 04-23-2009, 06:33 AM
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Default Re: vermiculate vs cement

Quote:
BTW, I used the silicone treated stuff and was able to get a very nice product
This is good to know, I'm only repeating what I heard about the silicone treated stuff. One of the reasons this forum is so valuable is that people share their experience with different products and processes.
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Old 04-23-2009, 02:49 PM
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Default Re: vermiculate vs cement

Well thanks for that guys, i will hold off and not do it after work today i will re read your replies and the attachments. At least I don't have to rush home and start up the mixxer.

the vermiculate i got was from a garden supply shop hope this is the right stuff cheers

P.s hope you all had good nights sleep I am off to work now cheers all
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Old 04-23-2009, 03:45 PM
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Default Re: vermiculate vs cement

Yep, you got the right vermiculite.
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Old 04-23-2009, 10:17 PM
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Default Re: vermiculate vs cement

The mix you are planning seems entirely wrong. It won't have any strength and it won't have much insulating value. Or maybe I'm misunderstanding you, maybe with some more explanation and a picture or two we could help more.

I've gone back and read your two previous posts, and I still don't understand. Please explain to us:

Did you start with a support slab? Is it reinforced? How thick is it? What concrete mix did you use for it?

Your vermiculite concrete layer: How thick is it? What proportions did you use to make it? How did you mix it? Did you use vermiculite from the garden supply, or silicone treated stuff made for domestic insulation?

Again, when we know more, we can help more.

Thanks dmun and all others

Yes 3.5 inch support slab with steel in it

vermiculate 4 inch

cement with 1-3 mix

mixxer and in a barrow

yes garden supply vermiculate
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Old 04-24-2009, 09:42 AM
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Default Re: vermiculate vs cement

From the plans:

Quote:
Prepare the insulating concrete using a ratio of 5 parts vermiculite to 1 part Portland cement (5:1). Mix the vermiculite and Portland cement, then add water and mix until you reach an oatmeal consistency.
Five to one is the largest ratio I've heard used, other makers have gone to 7:1 by pre-mixing the portland and water with a power paint mixer. Your three to one ratio may simply not have enough aggregate to do the job.

And make sure you are using portland cement, not one of the mortar or concrete mixes.
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Old 04-24-2009, 05:46 PM
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Default Re: vermiculate vs cement

You don't need the chicken wire.
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