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GIANLUCA 02-14-2013 12:16 PM

oven weight over vermiculite mix
 
I am planning all my thoughts out for a build this spring i have a question on the insulated hearth i get the 3.5" thick slab what i am wondering is about the insulating vermiculite/portland mix how hard does it dry and will it hold the weight of the oven base and dome i'm having thoughts that it is a fluffy kind of mix i was thinking that all the bricks will weigh it down causing it to shift. Will this be a problem or not?

vermiculite is readily available from and online store called "ULINE" it is a paper/shipping store it is sold by them for packaging hazzmat materials if a if a hazzardous material was to leak in transit the vermiculite would soak it up..interesting..

Tscarborough 02-14-2013 06:43 PM

Re: oven weight over vermiculite mix
 
You can build your oven on up to a 12 to one perlite if you put the walls on the floor and 8 to one if the floor is inside the walls, and still have a safety margin of hundreds of percent. The following chart shows up to 8-1 (which is the most I recommend for workability reasons, not compressive strength).

http://brokebrick.com/perlite.jpg

GIANLUCA 02-15-2013 02:49 PM

Re: oven weight over vermiculite mix
 
Thanks for the replies. I'm lost with the chart, I would like to hear of people who had there ovens sitting for a while through a couple winters.

stonecutter 02-15-2013 06:16 PM

Re: oven weight over vermiculite mix
 
Quote:

Originally Posted by GIANLUCA (Post 145651)
Thanks for the replies. I'm lost with the chart....

Just look at the first two boxes on the left...those are your cement/perlite(or vermiculite) ratios. Then go six boxes to the right ( compressive strength header).

Remember that standard concrete is right around 3000 psi ( normally) Tscar outlined a couple ratio parameters. I get that you want to hear first hand if someone did this, but there won't be a problem if you do it. In fact, in my current build, the whole oven...floors and walls, will rest on the insulating 'crete.

Tscarborough 02-15-2013 07:11 PM

Re: oven weight over vermiculite mix
 
To break it down. For a normal oven designed around the FB plans, you can mix 8 parts perlite/vermiculite* and get a floor that will easily hold the weight of the oven, is cheap and is also a very good insulator.

In the U.S., one bag of portland cement of 94+/- pounds equals one cubic foot of cement. Commercial perlite is usually packaged in 4 CuFt bags. 2 bags of perlite, plus 1 bag of portland and 16 gallons of water will net you 8 cubic feet of 90-125 PSI concrete upon which to build the oven. Don't try and mix it all at once.



*I have never worked with vermiculite so that is a guess and should be checked.

david s 02-15-2013 07:53 PM

Re: oven weight over vermiculite mix
 
Quote:

Originally Posted by Tscarborough (Post 145667)
To break it down. For a normal oven designed around the FB plans, you can mix 8 parts perlite/vermiculite* and get a floor that will easily hold the weight of the oven, is cheap and is also a very good insulator.

In the U.S., one bag of portland cement of 94+/- pounds equals one cubic foot of cement. Commercial perlite is usually packaged in 4 CuFt bags. 2 bags of perlite, plus 1 bag of portland and 16 gallons of water will net you 8 cubic feet of 90-125 PSI concrete upon which to build the oven. Don't try and mix it all at once.



*I have never worked with vermiculite so that is a guess and should be checked.

Expect around 20% reduction in volume once you've mixed it.


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