DIY castable refractory

[hamaxx]

I am sure this question has been asked and answered many time, but I have done many searches and forum reviews without any luck. I am interested in a mix design for home made castable refractory concrete. Interested in casting some panel sections for a wood oven project. Any help would be great. Thanks Rod - Wisconsin USA

[michelevit]

Re: DIY castable refractory

I've cast an oven with the following recipe.

1 part lime
1 part fireclay
1 part portand cement
3 parts sand.

Mix well dry.
Add minimum amount of H2O.
Cast away.

[david s]

Re: DIY castable refractory

I've cast an oven with the following recipe.

1 part lime
1 part fireclay
1 part portand cement
3 parts sand.

Mix well dry.
Add minimum amount of H2O.
Cast away.

Add some polypropylene fibres to the mix to assist in removing the water more safely.
Should probably add some stainless steel needles at 2% by weight too. They're called "melt extract fibres" in the trade.

[deejayoh]

Re: DIY castable refractory

I think for a pizza oven you want calcium aluminate cement instead of portland, and firebrick grog instead of clay (as aggregate). I think most instructions call for SS needles for strength as well.

[mikku]

Re: DIY castable refractory

If you are going through the effort of making good forms, don't waste your time with homebrew castable...buy the real stuff. It is not that expensive--my entire dome only took 9-25kg bags of castable for a 80mm thick 750mm inside diameter dome. I'd never screw around with a homebrew under any circumstances...if you value your forming time!

[michelevit]

Re: DIY castable refractory

how much was 9-25kg bags?

[mikku]

Re: DIY castable refractory

Equivalent of 252 US dollars, probably cheaper where you are. Japan is usually two to three times higher than anywhere else.

[david s]

Re: DIY castable refractory

If you are going through the effort of making good forms, don't waste your time with homebrew castable...buy the real stuff. It is not that expensive--my entire dome only took 9-25kg bags of castable for a 80mm thick 750mm inside diameter dome. I'd never screw around with a homebrew under any circumstances...if you value your forming time!

Unless you are planning on making several castings from the one mould, creating "good forms" is a waste of time IMO. It is easier to make a single cast over a sand castle, so quick and easy.

[mikku]

Re: DIY castable refractory

Well we disagree on another topic.

If a job is worth doing, why not try to do it right?

And, how many people know the first time around exactly what they want?

If you make a decent form, you can modify it if you do not like the first results. But with your "so easy- sand method, you have to start from scratch--or more specifically dirt".

So the "so quick" now becomes "so slow"! And there is no consistency.

But that is IMHO!

[david s]

Re: DIY castable refractory

You did a fine job building your moulds, I was in no way being critical of your work.. However, they must have taken you many hours to build and prepare for casting. How many castings have you produced from them since? A sand castle mould is so fast to make that you can complete the sand part of it in around an hour. If the intention is to create a single casting this method is far less labour intensive. Builders can make up their own minds how to do it.

[michelevit]

Re: DIY castable refractory

I've built using sand mold and can attest that it is a good way to cast an oven.
I also used the homebrew recipe and found it perfect for my needs.
We're not building a bridge- we're building an oven.

[mikku]

Re: DIY castable refractory

When you add up the costs of your components, what does your homebrew cost per 25kg?

How much time did it take to scurry around and find the ingredients from the different sources?

How much time does it take to accurately measure the proportions so that you get a consistent blend between batches?

With the premix castable, it is a rush to mix to the times stated and place the material. But the result is a glass smooth casting that is superior in appearance to the ones marketed in Ireland that need multiple scribes and cuts to come into alignment.

If I am doing a "homemade" project, I'd like it to turn out equal or better than the manufactured units, otherwise it isn't worth the effort!

Is 250 dollars too much to pay for a 225kg casting?

I see using homebrew as having too many variables to produce a predictable consistent product. Sourcing the ingredients and making sure each is fresh and clean without other contaminants IMHO isn't worth the effort.

[mikku]

Re: DIY castable refractory

Davids,
The question brought up was about the homebrew. Do you use homebrew in the ovens that you manufacture for sale? Do you use sand molds for the domes and special transition pieces that you manufacture? Or only in the prototype stage when you are trying to figure out what you want something to look like?

I did not see you as being critical of my form building, I probably would use sand at some point if I am trying to create something different. Gee whiz, they use sand all the time to make precision machine parts cast from a variety of materials--but I think we are talking about two different sand castings--aren't we?

[michelevit]

Re: DIY castable refractory

When you add up the costs of your components, what does your homebrew cost per 25kg?

Much much less than the premade...

How much time did it take to scurry around and find the ingredients from the different sources?

i have a material supply store that carries all the ingredianent (sand, portland, lime and fireclay) so no scurrying around. Just ask for what I need at the counter and its loaded into my car. Also free donuts and coffee if I go in the morning.


How much time does it take to accurately measure the proportions so that you get a consistent blend between batches?

not long at all.

One scoop cement,
One scoop sand
one scoop lime,
one scoot sand
one scoop fireclay.
one scoot sand.

mix dry and add minimal water.


Homebrew works just fine.


With the premix castable, it is a rush to mix to the times stated and place the material. But the result is a glass smooth casting that is superior in appearance to the ones marketed in Ireland that need multiple scribes and cuts to come into alignment.

If I am doing a "homemade" project, I'd like it to turn out equal or better than the manufactured units, otherwise it isn't worth the effort!

Is 250 dollars too much to pay for a 225kg casting?

I see using homebrew as having too many variables to produce a predictable consistent product. Sourcing the ingredients and making sure each is fresh and clean without other contaminants IMHO isn't worth the effort.[/QUOTE]

[mikku]

Re: DIY castable refractory

The homebrew you are describing has no aggregate so it must be like soup. The portland cement as described all over this forum is not a refractory material. But if you insist on calling this slurry refractory then so be it! I don't do things like you do--a little bit of this and a little bit of that. So we have some basic differences.

Enjoy your coffee and donuts