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aeu99217 06-21-2010 11:43 AM

aerated concrete blocks
 
Hi,

I was wondering if anyone could shed some light on the suitability of using aerated concrete blocks instead of fb or vermiculite concrete for the insulation hearth.

Any guidance would be great.

Cheers Ross:)

aeu99217 06-22-2010 01:48 PM

Re: aerated concrete blocks
 
In wiki it says it is used for insulation and that it is fire resistant.

Aerated autoclaved concrete - Wikipedia, the free encyclopedia

Has anyone used these before?

Any help would be greatly appreciated.

Cheers Ross:)

aeu99217 06-22-2010 01:56 PM

Re: aerated concrete blocks
 
I also found this website

Aerated Concrete, Lightweight Concrete, Cellular Concrete and Foamed Concrete

Which seems to suggest to me that they could even be used instead of firebricks.

'In tests undertaken in Australia, a LITEBUILT® aerated lightweight concrete wall panel, 150 mm (6") in thickness was exposed to temperatures in the vicinity of 1200°C (2192°F), with the unexposed surface only increasing by 46°C (115°F) after 5 hours. '

Is this the panacea of pizza oven builders in the uk? :)

Cheers Ross

GianniFocaccia 06-22-2010 02:09 PM

Re: aerated concrete blocks
 
Haven't heard of anyone using it. Although it's structure looks ideal for oven insulation (http://web.dcp.ufl.edu/stroh/AAConcrete.pdf), it's tolerance of thermal cycling isn't apparent, nor is it's compressive strength. It might be acceptable to use under 2" of insulation board, but why not just go the vermicrete route?

The desired properties of firebricks is to load them with heat so they can return the energy via radiation into your food. How long did the wall stay hot?

aeu99217 06-22-2010 02:43 PM

Re: aerated concrete blocks
 
Hi Gianni,

This is what it says about compressive strength

Density Kg/m3 300 400 500 600 700 800 900 1000 1100 1200 1400 1600
Sand - Cement
Ratio 0:1 0:1 0:1 0:1 1:1 1:1 1:1 1:1 2:1 2:1 2:1 3:1 3:1 3:1 3:1
7 Days
Mpa 0.3 0.8 2.0 3.5 0.8 1.4 2.5 3.0 1.4 2.2 3.8 3.0 4.0 8.0 10.0
28 days
Mpa 0.7 2.0 3.5 4.0 2.0 3.5 4.5 5.0 3.2 5.2 8.5 7.0 10.0 12.0 18.0

Unfortunately it means nothing to me :)

I also found this

Having high thermal mass means that blocks have a capacity to absorb and release energy slowly over time. It is a very important element for providing high indoor living comfort because it prevents rapid temperature swings caused by extreme daily outdoor temperatures and eliminates constant cycling of the heating or cooling system to maintain the preset temperature.

AAC modules feature an R-value of approximately 1.25 per inch but exact R values vary by thickness and geographical location of construction. From my research I found out that there are tables that illustrate what Equivalent R-Values would be for different thicknesses of the AAC block and the geographic location where they are being installed. This data is compiled by AACPA (Autoclaved Aerated Concrete Products Association). Refer to their site for more information. For example, a 10" AAC installed in Denver provides an Equivalent R Value of 20.16.

Again doesn't mean much to me.

They're only a quid for a brick, so cheap in comparison to buying and having to mix etc the vermicrete. However, im more interested in their suitability for the dome. It didnt say in that test how long it stayed hot for. I'll need to do a bit more research. :)

fxpose 06-22-2010 03:03 PM

Re: aerated concrete blocks
 
AAC was used in this build:
http://www.fornobravo.com/forum/f43/...dah-12821.html

dmun 06-22-2010 05:33 PM

Re: aerated concrete blocks
 
There have been many discussions on this topic.
It's kind of moot to us because they are not available at retail in the US.

The bottom line: they are not quite as good an insulator as vermiculite concrete, but in europe they are a cost effective solution if you have the space for six inches of insulation. They are brittle, and easily damaged. And no, they won't do inside of the oven, as they can't have thermal mass and insulation qualities both.

BackyardPermaculture 06-22-2010 05:42 PM

Re: aerated concrete blocks
 
Hi Ross,

As mentioned above, I used AAC here in Australia. They were cheap and quick, and they seem to insulate really well. I can't feel any warmth under my oven for several hours when it's firing, so I don't think you can fault the insulating performance. After 5 hours I can feel warmth, but it's not hot.

They were definitely really brittle - transport with care, because the edges and corners chip easily. You couldn't use them anywhere that they could get knocked; mine are hidden away under tiles.

I also don't know what happens to them long-term from the heat. But perhaps not much different to vermicrete; both of them are depending on portland cement.

Cheers, Mick.

aeu99217 06-23-2010 02:49 PM

Re: aerated concrete blocks
 
Nice one. Cheers guys. Think I'll definitely go down the aac route for the insulation hearth and cover them with tiles.

Thanks again :)


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