Corner Pompei Oven following Forno Bravo instructions-Loei Thailand

[Garouda]

The sand/clay levelling mix is better left dry because if a floor brick needs to be replaced at a later date, the wet mix sets very hard like mortar, but the dry mix will not. It allows for expansion and contraction of individual bricks.

Thanks, David, I was about to fall into the trap...
What should be the sand/clay mix ratio?
Does it make sense to cut the bricks on the fly?
I initially placed my bricks on my parking floor and marked the shape using the template I made for the vermiculite insulation mix, but I fear the bricks will not fit the same way once in place if I cut them in advance.

[Mr.Pizza3]

More on vermiculite ratios here

https://community.fornobravo.com/for...e-cement-ratio

[Mr.Pizza3]

My plan for the spaces was to either back fill with a dry clay sand mixture or just let the ash slowly fill in the floor

[david s]

The sand/clay levelling mix is better left dry because if a floor brick needs to be replaced at a later date, the wet mix sets very hard like mortar, but the dry mix will not. It allows for expansion and contraction of individual bricks.
Most builder recommend a 5:1 vermicrete for the under floor insulation mix because of the weight it has to support. A 10:1 mix over the dome is more suitable though because it only needs to be firm enough to stucco against.
. The accompanying table shows relative strength and insulation values which explains the appropriate ratio for under or over the oven.

[Garouda]

Not sure if you poured your v-Crete yet, but I went with an 8-9 : 1 ratio for my v-Crete gave it is a light compaction, and it turned out great for me better insulation properties then 5:1 too I know a few builders here have gone as high as 10 : 1

dry mix first then slowly add your water as well, keep it dry!

Many thanks, I unfortunately already poured two bags, but it appeared to be not sufficient. The vermiculite I found did have lots of broken kernels and dust, also I suspect the seller to fill the bags by weight and not by volume. The volume I calculated was 150 litres, and two 100-litre bags did not fill it...
I guess it's 8:1:2 eight volumes of vermiculite, one of Portland and two of water to have enough water for the chemical reaction.
In the meantime, I prepared the bricks for the oven floor. If there are spaces, can I pour refractory cast concrete, or refractory clay?
For the formwork, 'KISS', four F clamps, four planks and the scraps from the template cutout to hold the circle in place. A cast aluminium water level that has followed me faithfully for more than 45 years...

[Mr.Pizza3]

Not sure if you poured your v-Crete yet but I went with a 8-9 : 1 ratio for my v-Crete gave it it a light compaction and it turned out great for me better insulation properties then 5:1 too I know a few builders here have gone as high as 10 : 1

dry mix first then slowly add your water as well keep it dry!

[Garouda]

This doc may be of some use to you.

[ATTACH]n453547[/ATTACH]

Very informative, indeed. Thank you very much.

[david s]

This doc may be of some use to you.

Vermicrete insulating slab PDF copy.pdf

[Garouda]

The vermiculite has been delivered, the formwork is done, I took the cuts from the floor template to hold the circle in place and four wooden planks locked with four F-clamps made a frame to hold everything in place. I bought a tent for both sun and rain. I got short of vermiculite... I calculated a volume of 150 litres, but the two 100-litre bags were not enough, they seem to have a different definition of the litre down here...
Total volume: 71 cm x 43 cm x 10 cm = 30530 cm3 and 123 cm / 2 at the power of 2 x 3.14159 x 10 cm = 118823 cm3 : total 150 212.8 cm3 or 150 litres... A piece of advice, take some empty beer bottles you must have somewhere in a corner, break them in small parts to have about a 1/2" layer, and you won't risk being facing the same issue with your vermiculite. I did not consider that problem and of course, I'm not going to put glass as first layer under the refractory bricks...
Breaking News... I checked the website of that company, they also sell 60-litre bags, in other words the seller on the online shopping channel cheated me and sent me 60-litre bags for the price of 100-litre bags!

[Garouda]

Next step, the formwork template it's frankly speaking too hot to work outside now, even in the shade. Normally in this period of the year we have rain, but the seasons have hanged.

[Garouda]

I used Hebel Power Panel for the supporting slab for my mobile oven in the belief that it would be both strong enough and acting as sufficient underfloor insulation. It turned out not to be, but I think it's probably OK in a stationary situation.
See here
https://community.fornobravo.com/for...ion#post398266

Thank you for the link, anyhow, I thought about it too late, I have already poured my concrete slab. In my case, there are anyway prefabricated slabs which I used as formwork and which would have supported the blocks of autoclaved aerated concrete, which we call Ytong in Europe because that brand is the name of the Swedish village where the process was invented in 1938 if I well remember.
I found a project that is more or less in line to what I would have done, but with two layers of 7 cm blocks, he uses 5 cm blocks which IMHO is too thin. I would have used 15 cm blocks, but we can hardly find them in my remote province of Loei, in the NE of Thailand, 40 km from the Mekong River…
https://community.fornobravo.com/for...-build?t=14444.

[david s]

I used Hebel Power Panel for the supporting slab for my mobile oven in the belief that it would be both strong enough as well as acting as sufficient underfloor insulation. It turned out not to be, but I think it's probably ok in a stationary situation.
See here
https://community.fornobravo.com/for...ion#post398266

[Garouda]

Anyone has an oven floor template for a 40" oven? I'd need drawing plans to build the vermiculite formwork for the floor.
I've seen some differences on the templates, and not sure why some have straight openings and some have a bit of a diagonal opening.
Any thoughts?

[Garouda]

..Hebel which is an aerated concrete has been used a bit by our Aussie builders as a base layer. I am not sure how much heat Hebel or aerated concrete can handle, though.

Autoclaved aerated concrete provides the highest security against fire and meets the most stringent fire safety requirements. Due to its purely mineral composition, AAC(aka Hebel here, Ytong in Europe after the name of the Swedish village where that process was invented in 1938?) is classified as a non-combustible building material. It is both resistant to fire up to 1200 °C and, unlike other construction materials, heat-resistant.
Source: https://eaaca.org/fire-resistance/
And, as I wrote earlier, AAC offers almost the same heat resistance as Vermiculite...
But for me, it's too late, I'm going to build that insulation part of the hearth in vermiculite like here: https://youtu.be/v-neyYcCmU4
My concern about that video is that the first template he shows at the beginning of the video is longer that the one he actually uses in the end.
I this a correct drawing (see picture)?

[UtahBeehiver]

Square or rectangular shape, just dimensional wood form, circular, landscape bender board. Be sure to install weep holes in the concrete hearth, especially since you are in a tropical area.