brickless dome on a shoestring oven

[v12spirit]

Re: brickless dome on a shoestring oven

While rebar reinforcing may seem like a great idea to increase strength, remember that heat will accelerate any corrosive reaction. I think rust will eventually prove to be the undoing of this idea in the long term. When rebar rusts substantially it increases in volume producing stress cracks in the refractory material. The standard reinforcing for refractory is stainless steel needles presumably for the previously mentioned reason.

Hi david s
Do you mean that the needles are just spread randomly in the concrete mix without shaping them into a lattice? I have plenty of 2" stainless steel nails can I just add them to the mix?
How about a chicken wire made of aluminated zinc?

[david s]

Re: brickless dome on a shoestring oven

yes the needles are spread randomly. They are around 0.5mm thick. Not sure how anything thicker would go, but my guess is that thicker material will attract heat to itself and therefore be hotter meaning more thermal expansion than the material that is surrounding it. This would lead to stressing the refractory. Not sure what thickness you could get away with for this application. The nails could work, but will make the mix hard to handle. I think the zinged chicken wire may corrode. Zinc has a melting point around 400 C

[cannyfradock]

Re: brickless dome on a shoestring oven

...many of the European modular oven manufacturers are turning to heat resistant carbon fibre rods to strengthen their refractory concrete segments. As manufacturers try to reduce the weight of their ovens, the 6mm rods suit the purpose as they can be easily bent into any form. They are available to "Joe public" and cost about ?10 (UK) for a 5 meter length.

....wouldn't suit a " brickless dome on a shoestring oven" as it would defeat the object, but it's an alternative to s/s needles.

Terry

[di11on]

Re: brickless dome on a shoestring oven

The oven has no cracks and performs beautifully.
I recommend this build for anyone looking to build a low cost simple oven. Many fires and pizza have been built in it with no signs of failure.

Not sure why so many people are doubting its construction.

Feel free to build what you like. I was just trying to share a design that worked for me.

The goal was shoestring budget. I met the goal.

Hi Mich,

Just wondering - do I understand correctly that your homebrew castable mix had no coarse aggregate in it? As in, simply the portland, lime, clay and sand and nothing else?

I'm considering making one myself and was thinking of doing something similar... most of the receipes I've seen using ciment fondu use grog/crushed brick which is difficult for me to get.

Also, I don't have access to welding equipment - I was thinking of doing it in segments like here for example: Four ? pain en quartiers d'orange - the thinking being the expansion joints would prevent cracking.

Any thoughts, particularly about the absence of a coarse aggregate (eg grog).

Cheers

[cobblerdave]

Re: brickless dome on a shoestring oven

G'day
There a product called "crusher dust" basically the washings from gravel production. The size varies from 2 to 3 mm down to dust. Its usually used as a stable base as it packs down well and I've used it as the base under bricks in my driveway.
I know it gets used in Aust as the "grog" component with cement fondue for home caste domes. Its cheap and available. So you might want to check out a few gravel yards.
Regards dave

[wotavidone]

Re: brickless dome on a shoestring oven

Crusher dust is brilliant stuff. It rolls/packs very hard, and it truly is as cheap as chips. It's about 20 dollars ffor a bobcat bucket here - and that would be enough for a quite large oven.
The toughest thing with crusher dust is deciding the ratio of crusher dust to ciment fondue. I've never figured it out.
It has small rocks and fines in it. Do you seive it and decide the proportions of fines and rocks, and decide how much cement based on the fines portion, or do you just say what the hell and mix it say 3 to 1 with the ciment fondue?

[david s]

Re: brickless dome on a shoestring oven

My refractory supplier tells me that many chimneys are lined internally with a mix of fondu and cracker dust. I have no idea about its suitability as a castable for a WFO. Someone try it out, use it for 10 years and report back.

[cobblerdave]

Re: brickless dome on a shoestring oven

G'day Mick
Spoke to Rossco about his caste oven and the ratio of ciment to crusher dust. Its been three years now and he can't remember exactly. He followed on the proportions of the home brew mix so he thinks its 1 to 3 because he disregarded the clay and lime component.
G'day Davids
Well there's 2 of these caste ovens in Brisbane. Both 3 years old and still working well. Rossco says his dome is holding up well and his only concern is the firebrick hearth that has developed some cracks and lots of chipped corners.
I hope to see Rossco and his oven sometime soon and I try to get him to post some recent pics
Regards dave

[michelevit]

Re: brickless dome on a shoestring oven

Hi Mich,

Just wondering - do I understand correctly that your homebrew castable mix had no coarse aggregate in it? As in, simply the portland, lime, clay and sand and nothing else?


Cheers

Yes/ That is correct. portland, lime, clay and sand. Oven still perfect. Works great.

[cobblerdave]

Re: brickless dome on a shoestring oven

Yes/ That is correct. portland, lime, clay and sand. Oven still perfect. Works great.

G'day
Just wondering have you got some recent pics?
I'd really love to see some
Regards dave

[almondsurf]

Re: brickless dome on a shoestring oven

Just wondering if I could seccond that of Dave... Have any recent pictures?

I'm tossing the idea of castable (like yours) or using brick. I will probubly be using the 'stainless steel needles' rather than rebar.

[vertigopilot]

Re: brickless dome on a shoestring oven

Greetings, fellow oven builders.

On the debate whether a homebrew-refractory dome can withstand the stresses of long-terms use, I would like to add to the discussion that I built a brickless-dome oven in 2007 for a friend that is still in use today without any cracks or failure.

My mix was 10 parts silica sand, 10 parts pea gravel, 3 parts fireclay, 3 parts hydrated lime, and 2 parts regular Portland cement. No rebar was used.

My most recent oven project is a barrel-vaulted design using firebricks and a mortar of roughly the same recipe (minus the pea gravel of course). It was a 21-day build and has been continuously hot from the day it was first fired about two weeks ago.

-Jim

[di11on]

Re: brickless dome on a shoestring oven

Greetings, fellow oven builders.

On the debate whether a homebrew-refractory dome can withstand the stresses of long-terms use, I would like to add to the discussion that I built a brickless-dome oven in 2007 for a friend that is still in use today without any cracks or failure.

My mix was 10 parts silica sand, 10 parts pea gravel, 3 parts fireclay, 3 parts hydrated lime, and 2 parts regular Portland cement. No rebar was used.

My most recent oven project is a barrel-vaulted design using firebricks and a mortar of roughly the same recipe (minus the pea gravel of course). It was a 21-day build and has been continuously hot from the day it was first fired about two weeks ago.

-Jim

Thanks for this Jim. I may very well give this a go for my next build... that is, if moving my previous build proves disastrous!

[vertigopilot]

Re: brickless dome on a shoestring oven

Thanks for this Jim. I may very well give this a go for my next build... that is, if moving my previous build proves disastrous!

That looks like a very nicely-built oven. I'd hate to think of trying to move mine - it weighs at least 5 tons!

[juanbe]

Hi michelevit,
I´m new in this community, and your post impressed me.
Only one question....since 2009 when you constructed this oven, its still performing great and showing no signs of failure?
Thanks very much.
Regards.