Lava?

[JeremyM]

Re: Lava?

So has anyone done further R&D with the pumicrete or lava rock in their oven?

[asudavew]

Re: Lava?

The vermiculite layer can be easily trimmed and removed, you don't have to make a form exactly, even just enclosing it in a square form will work. After a couple of days remove the form and trim with a straight edge. Shovel, plaster knife (old one), brick trowel or what ever. If you time it right its just like cutting a rice crispy treat. Someone posted pic of them trimming it back but I cannot remember who or where.

Thanks Uno,

But I already built my oven shaped form and poured the perlite insulating slab.

I was pleased with the results.

[Unofornaio]

Re: Lava?

Now I just have to work out the details.......... like creating an oven shaped form....

The vermiculite layer can be easily trimmed and removed, you don't have to make a form exactly, even just enclosing it in a square form will work. After a couple of days remove the form and trim with a straight edge. Shovel, plaster knife (old one), brick trowel or what ever. If you time it right its just like cutting a rice crispy treat. Someone posted pic of them trimming it back but I cannot remember who or where.

[Unofornaio]

Re: Lava?

I'm anxious to hear how the final product works out. I bet the insulating layer with lava will have more strength vs the vermiculite which would make it a better platform for building on top of. I think I read somewhere that the vermiculite concrete wasnt very strong and wouldnt hold an anchor bolt.

thanks for doing all the research.

>If you need to embed an anchor bolt the place to do it is in the concrete layer and have it long enough to come up through the insulation layer. Then add a plate to distribute the load in the bolt area.

[mastergene]

Re: Lava?

Scoria - Wikipedia, the free encyclopedia

Pumice is widely used to make lightweight concrete or insulative low-density 'breeze-block' type bricks. When used as an additive for cement, a fine-grained version of pumice called pozzolan is mixed with lime to form a light-weight, smooth, plaster-like concrete. This form of concrete was used as far back as Roman times.

It is also used as an abrasive, especially in polishes, cosmetics exfoliants, and for stone-washed jeans. "Pumice stones" are often used in salons during the pedicure process to remove dry and excess skin from the bottom of the foot and also calluses. Finely ground pumice is added to some toothpastes and heavy-duty hand cleaners as a mild abrasive. Perhaps the most famous product advertised to contain pumice is Lava soap. It is a heavy-duty hand soap, sold in both bar and liquid form, for mechanics and others who get very dirty hands.

[asudavew]

Re: Lava?

It does make very strong bricks!

And I like the idea of a strong foundation for the oven.

I want my insulation to sit only under the oven, because I like the appearance of a 3 1/2 inch hearth.

Now I just have to work out the details.......... like creating an oven shaped form....


I'll keep you informed Kemo.

[Kemo]

Re: Lava?

I'm anxious to hear how the final product works out. I bet the insulating layer with lava will have more strength vs the vermiculite which would make it a better platform for building on top of. I think I read somewhere that the vermiculite concrete wasnt very strong and wouldnt hold an anchor bolt.

thanks for doing all the research.

[asudavew]

Re: Lava?

I'm still thinking about using lava rocks..

I took a bunch and made a brick out of lava rocks and cement. Then I let them cure a few days.

The only test I could think of was putting half of the brick in my gas BBQ. So thats what I did.

The bbq was over 600 degrees F and the half brick on the inside was hot enough to turn water to steam, but the half brick sticking out was still cool to the touch.

I think it would work fine! Just don't want to make an insulating error.

[Archena]

Re: Lava?

Green Home Building: Natural Building Techniques: Lightweight Concrete

"Pumicecrete" has an R factor of ~ 1.5 / inch.


Edit: Note to self - read both pages first!

<insert slapping forehead smilie here>

[Bacterium]

Re: Lava?

I like the ingenuity of this forum?..

Thanks Dave,
It sounds like you have a similar situation to me in that the oven is not seen as much of a ?financial priority? so I had to be resourceful with mine as well

[asudavew]

Re: Lava?

To show how hot this piece got I had some shots taken without the flash.

Thanks to my daughter Harley for taking the pictures.

I was still holding it with my hand for several minutes.

It never got hot on the other side.

I figured out the ratios, and it looks like 2 parts water 5 parts lava rock and 3 parts cement gives the best k value.

[asudavew]

Re: Lava?

Here are some pics of me blow torching a piece of lava rock/scoria (Thanks Bacterium!)

These first few are with the flash on.

[asudavew]

Re: Lava?

I found a study that showed the k value of a cement/scoria mixture. Man that took a while.

The study found that k values range from .252 - .174 depending on the ratio of materials.
So I think it looks pretty good.

Here's a link to the study. K values are on page 10 I think.

http://www.academicjournals.org/IJPS/PDF/Pdf2006/Sep/Hossain.pdf

Thanks for the input, I would never would have thought about looking into K values.

[maver]

Re: Lava?

I'm not sure the blow torch test is relevant - the time factor with a pizza oven is a bit different. I tried to find comparison K values for lava, the only one I could find with google showed a K value around 2, compared with 0.5 for superisol and about 0.6-0.7 for perlcrete or vermiculite cement. I was unable to verify (tried searching here for the old discussion of K values but could not find it) whether these are the same units. I'd do a bit more background work before moving to a different insulation material - is perlite or vermiculite really that expensive by comparison?

Marc

[asudavew]

Re: Lava?

Yeah

That is what I am thinking.

And I'm trying to build on the cheap.... 5 kids at home




Plus I wanted a stronger insulating layer under my dome.

I think this may work, I'm gonna try to build some test blocks tonite.