New 36inch castable build in Brisbane

[brissie]

Re: New 36inch castable build in Brisbane

Decided to add extra thickness to the insulation. I used a box of 6.2M * 600* 25mm ceramic fibre, that worked out as 50mm over most of the dome, and 100mm of 10:1 Vermiculite over the fibre. I added concrete supports on the two sides. Galvanised screws into the hebel and concrete help support the extra dome width.

A screed pivot rod fits into a dimple in the castable. It was slightly out of centre, so needed to bend the rod to centre it.

Photos below.

[chubbybones]

Re: New 36inch castable build in Brisbane

This is a very interesting build brissie,keep up the great work.

[brickie in oz]

Re: New 36inch castable build in Brisbane

Fibre glass rope is available,

I melted some on my oven entry....

[oasiscdm]

Re: New 36inch castable build in Brisbane

There's a few places in Melbourne that do Google ceramic and refractory Victoria.

[brissie]

Re: New 36inch castable build in Brisbane

I'm not sure if you are leaving the backer rod in place, but if you do, it will melt. Ceramic rope works well as expansion gasket,and you can slurry paint it to encapsulate the fibers. Looking good..this has got me interested in casting a dome.

No the rubber is out, The ceramic rope sounds good if you can protect the fibres. Can't seam to find ceramic rope in Aus, haven't looked to hard though. Fibre glass rope is available, the temperature rating is 500 C, 1000 F. Not sure if 500 C temp would be good enough, with heat going up the flue.

[stonecutter]

Re: New 36inch castable build in Brisbane

I'm not sure if you are leaving the backer rod in place, but if you do, it will melt. Ceramic rope works well as expansion gasket,and you can slurry paint it to encapsulate the fibers. Looking good..this has got me interested in casting a dome.

[brissie]

Re: New 36inch castable build in Brisbane

Filled the hole it the dome wit castable, and first heat break with 5:1 vermiculite sieved castable. I also covered this with a layer of standard 5:1 vermiculite and Portland cement. You can see the expansion joint in the photos.

I also completed the arch.

[brissie]

Re: New 36inch castable build in Brisbane

This area gets pretty hot. It will be hot enough to destroy Portland cement, use the sifted castable.For the mix between the entry and the outer decorative arch, Portland and vermiculite is ok.

Thanks for the reminder David s,

I was planning on implementing your good advice. I didn't bother with the lower part of first heat break on the floor. If the cement burns away it will still have the vermiculite in place as an insulator.

[david s]

Re: New 36inch castable build in Brisbane

Brissie,
Just had a second thought since you were asking about temp in the entry.
My heartbreak is actually between the flue gallery and the outer decorative arch. In that position vermicrete holds up ok , however if you put it between the dome and the flue gallery it is considerably hotter there. If it were me doing a vermicrete mix there I'd use some castable with the aggregate sieved out of it to mix with the vermiculite rather than using a Portland cement mix.
Dave

This area gets pretty hot. It will be hot enough to destroy Portland cement, use the sifted castable.For the mix between the entry and the outer decorative arch, Portland and vermiculite is ok.

[brissie]

Re: New 36inch castable build in Brisbane

More photos,

[brissie]

Re: New 36inch castable build in Brisbane

Weekend #4,

I went shopping for arch bricks today, we picked some that are dark in colour, they are seconds at $1 each. The plan is make the decorative arch tomorrow.

I have the dome in place with heat break number 1 and additional support for the dome 5:1 vermiculite concrete. The CalSill board is only 1 meter wide, so added extra support for 80mm walls.

You can see the 10:1 vermiculite insulating in the heat break. The gap at the top is 2 or 3 mm, and should not be an operational problem. the gap will fill with ash. ( thanks David s for the idea ).

The brick slabs had horrible edges. So needed to take off the edge with the grinder. If I did this again I would look at standard fire bricks, I think they give a better finish. The dome was easy to put together with the help of my son, we stuck the dome together with corfix 900 degree mastic, and did not seal the dome to the base to allow for expansion.

The hole in the top will be filled with castable tomorrow. I will use the remainder of the castable to patch over the joins in the dome. I started with 12 * 20 kg bags. This quantity is about the correct amount for 80mm thick 900mm/36 inch oven.

[mikku]

Re: New 36inch castable build in Brisbane

Thanks for the comments mikku,

I think because the paper was wet and only a couple of layers thick, I should have gone a lot slower. Note that the imperfections are not deep. More care is needed to keep the paper stable. I think functionally it would work as is, but I will try and clean it up a bit. You can also see the texture change after around the first 100 mm, so the amount of water added does make a difference.

Perhaps I should have added more water. but this also reduces strength.

The ratios for the mixture are pretty specific with the stuff that I was using. Think more important is getting the stuff packed tightly when you are hand working it. But this is a guess only. Davids comments on sifting out aggregate from regular mix to make a peanut butter consistency patch material sounds good. The stuff does set overnight so I am thinking it is very important to get the patching done before too long.

As others have said and I agree, nothing to worry about structurally! But just because someone else does not see any imperfections does not make them disappear...you have to satisfy yourself first! If it to your expectation, then nothing else matters!

Keep up the good work.

[stonecutter]

Re: New 36inch castable build in Brisbane

I think a brick oven interior is a lot rougher than that. Ever see the inside of professionally built Neapolitan ovens? Most of the ones I have seen have rough brickwork...your surface is more smooth.

[david s]

Re: New 36inch castable build in Brisbane

Hi Brissie,
I've never had the problem of the newspaper slipping, but then I've only used newspaper and water. As you also used oil this may have caused the problem. Any embedded newspaper will just burn away. You can leave it, the surface looks pretty good to me. If you have any voids to fill you can sieve out the course aggregate from some dry castable and mix a little water to the sifted castable that is left, to a peanut butter consistency. This mix can then be squished and smoothed into any voids. You need to do this operation before the casting gets completely dry. The day after removing from the mould is usually about right.

[cobblerdave]

Re: New 36inch castable build in Brisbane

Thanks for the comments mikku,

I think because the paper was wet and only a couple of layers thick, I should have gone a lot slower. Note that the imperfections are not deep. More care is needed to keep the paper stable. I think functionally it would work as is, but I will try and clean it up a bit. You can also see the texture change after around the first 100 mm, so the amount of water added does make a difference.

Perhaps I should have added more water. but this also reduces strength.

G'day Brissie
When I first read you post that the paper had slipped I feared the worst.
Now the pics have eased my mind. That's not that bad at all. Definitly not a bad structural fault at all . As for the look of it, its nice and smooth so doesn't look bad at all. The dome is perhaps the most important part along with insulation.
But the least seen. No one will ever see that " imperfection"
Hang in there
Regards dave