#11  
Old 02-10-2013, 10:28 AM
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Default Re: Recycled Insulation, any thoughts or warnings?

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Originally Posted by Thailandnotes View Post
OK. I cut the insulation brick in half. A half of one is about 3.5 inches thick. I laid out a firebrick frame and laid the insulating bricks inside. The bricks are 1/2 an inch higher than the insulation. Can you pour a 1/2 inch layer of concrete without it cracking (wire mesh?)?
When you say "concrete" I hope you are referring to the refractory homebrew (a 3:1:1:1 mix of sand, fire clay, lime and Portland cement frequently recommended on this site) or one of the commercially available refractory mortar or cement mixes. Standard concrete will not hold up to the heat (it will breakdown when temperatures exceed 600F).

The homebrew and mortar mixes are intended for use between bricks and are not generally used at thicknesses greater than 1/2" where tensile loading will take place. However the tensile limitations of this material will not be a factor in your application because your "concrete"/mortar layer will be under compression (trapped between your insulation and Firebrick hearth).

If I were you, I would make your "concrete"/mortar layer approximately 3/8" thick leaving room for some sand and fireclay underneath your firebrick to help in leveling the hearth (reference David's post above).

What size are your firebricks? Reading your post above it sounds like you have some very large bricks (1/2" thicker than your 3.5" insulation) or are you laying your FB on their sides? Also are you planning to build your dome on top of the hearth floor or will the hearth bricks be cut to fit inside your dome? Maybe some pictures would help.

Regards,
AT
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  #12  
Old 02-13-2013, 07:14 PM
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Default Re: Recycled Insulation, any thoughts or warnings?

These firebricks are slightly larger than what you would find in the states. I surrounded the insulation blocks with the bricks, then covered the insulation blocks with a thin layer of sand to fill in nicks and slots. Then I used a 6/1 perlite/refractory cement mix to cover that.

I have a hard time believing this is sealing anything, but I'm a rookie.
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Recycled Insulation, any thoughts or warnings?-sand-covering-insulation-blocks.jpg   Recycled Insulation, any thoughts or warnings?-perlite-refractory.jpg  
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  #13  
Old 02-13-2013, 08:56 PM
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Default Re: Recycled Insulation, any thoughts or warnings?

Hey, we were all rookies once and even "experts" make mistakes (know anybody on Wall Street?). With what you've done so far I think you're golden.

Given the relatively uneven surface of the perlcrete insulation, I would recommend a 3-5 mm layer of sand to make life a little easier when laying your hearth bricks (many here would even recommend a 50/50 mix of sand and clay - I think the clay is supposed to make it easier to level).

Do you plan to build your dome on top of the hearth or are you going to cut your hearth bricks to fit inside the dome?

Looking forward to watching the rest of your build and I'm curious about the Thai recipes you have in store for us.

Good Luck,
AT
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  #14  
Old 03-13-2013, 03:09 AM
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Default Re: Recycled Insulation, any thoughts or warnings?

Ok, after laying the hearth, I'm on to beginning an arched opening and the dome. When I mixed the refractory cement with water and used it to test with four or five bricks, after it dried, I could pull the bricks apart and crush the dried cement back into a powder. Not good.

I mixed about 25 % Portland and 75 % refractory and that produced what I was hoping for, but before I go forward, I would like to read up on how refractory cement should behave, what adding to it might do down the line. I've looked on the internet and googled this site, but I'm hoping someone can provide a link so I can cut quick to the chase.

Comments and suggestions also appreciated.
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Old 03-13-2013, 04:12 AM
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Default Re: Recycled Insulation, any thoughts or warnings?

Quote:
Originally Posted by Thailandnotes View Post
OK. I cut the insulation brick in half. A half of one is about 3.5 inches thick. I laid out a firebrick frame and laid the insulating bricks inside. The bricks are 1/2 an inch higher than the insulation. Can you pour a 1/2 inch layer of concrete without it cracking (wire mesh?)?
I'd be pouring a 1/2" vermicrete slab over the insulating bricks, then if it is uneven lay a thin bed of 50/50 fireclay/sand over it before placing the firebrick floor.

Oops, sorry. I see you've already done it.

Last edited by david s; 03-13-2013 at 04:15 AM.
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