Homebrew Concrete for Homemade Kamado Cooker

[Pluffmud]

Is it feasable to create a Kamado Cooker (similar to a big green egg) out of the Homebrew concrete mix?
The mix is plan to use is
1 part lime
1 part fireclay
1 part calcium allumninate cement
3 parts sand
fiberglass strands mixed in for support

I am planning on having the cooker be 1" thick throughout. Is this too thin? Here is a video of what I am shooting towards

[Gulf]

Welcome to the forum, Pluffmud

Cool video! especially the carving of the forms. I can't really answer all of your questions, but I bet someone will come along that can. I am pretty sure that stainless steel concrete reinforcement needles are used instead of fiberglass. Until then you might could try a search of the site for "refractory cement".

[UtahBeehiver]

I think David S from Aussie land is a good source for a homemade cast Kamado oven. He does a lot with SS needles and cast refractory. Maybe he will see this post, if not send him a private message.

[david s]

The recommended reinforcing fibres for refractory castables are Melt extract fibres (stainless steel needles). If you want to use fibreglass fibres, not as strong as the stainless fibres, make sure you get the AR (alkaline resistant) ones containing a decent amount of zirconium (min 19%).

The use of lime in conjunction with calcium aluminate cement results in accelerated reaction which reduces the already limited working time. It begins to stiffen up as soon as t's been mixed properly. When using castable (without the lime) I always use chilled water in the summer for this reason, it extends working time. I wouldn't recommend using the two together in a castable brew for this reason. Anyone recommending this mix has obviously not tried it or the amount of mix made up has been extremely small.

[Pluffmud]

The recommended reinforcing fibres for refractory castables are Melt extract fibres (stainless steel needles). If you want to use fibreglass fibres, not as strong as the stainless fibres, make sure you get the AR (alkaline resistant) ones containing a decent amount of zirconium (min 19%).

The use of lime in conjunction with calcium aluminate cement results in accelerated reaction which reduces the already limited working time. It begins to stiffen up as soon as t's been mixed properly. When using castable (without the lime) I always use chilled water in the summer for this reason, it extends working time. I wouldn't recommend using the two together in a castable brew for this reason. Anyone recommending this mix has obviously not tried it or the amount of mix made up has been extremely small.

So I should remove the lime from the batch, because it decreases the work time. That makes sense.

Is the calcium aluminate cement used because standard cement degrades at high temps?

How smooth does this mix get after the castable has cured?

[david s]

So I should remove the lime from the batch, because it decreases the work time. That makes sense.

Is the calcium aluminate cement used because standard cement degrades at high temps?

How smooth does this mix get after the castable has cured?

Yes, normal portland cement begins to degrade at around 300 C. lime somewhat better, beginning to fail at around 400 C from memory, calcium aluminate better again.
Regarding smoothness of the mix, that depends on how fine your aggregate is, the castable I use has max aggregate of around 4mm, if using sand it should be good, but the surface against which you are casting determines how smooth the resulting casting will be. Make sure you use a release agent.

With a thin 1" casting random fibre reinforcement is mandatory IMO and mould vibration as well if you can arrange that.

[jamescornwall]

Is it feasable to create a Kamado Cooker (similar to a big green egg) out of the Homebrew concrete mix?
The mix is plan to use is
1 part lime
1 part fireclay
1 part calcium allumninate cement
3 parts sand
fiberglass strands mixed in for support

I am planning on having the cooker be 1" thick throughout. Is this too thin? Here is a video of what I am shooting towards

Wow you made that! I am well impressed, clever clogs! Well done mate

[Lburou]

There have been many castable ovens recorded here, something may crossover from those threads that would help you. You might find This, or This helpful. :-)

During a visit to my local refractory, I spoke with the owner and his engineer about a home made castable for my best friend working overseas where materials are not readily available. This is the home brew recipe they gave me -use at your own risk, your results maya vary

30% Ciment Fondu (calcium aluminate cement I'm sure you can get some)
60% Aggregate (#6 mesh -sizing 3mm down to powder)
5-10% Fine Sand
5-10% kyanite (crushed, Metamorphosed peri-aluminous sedimentary rock, optional, if not available locally-add more fine sand)

HTH

[African]

I know this is old but I'm interested in making my own kamado here soon and was wondering if anyone here has another recipe they would recommend and why? I was also wondering how you would remove all air gaps within the mold since the mix consistency is too thick to simply pour?