Your Advice Re: HomeBrew Castable Mix Greatly Appreciated

[stonecutter]

Re: Your Advice Re: HomeBrew Castable Mix Greatly Appreciated

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We'd much prefer to create our own "home brew" castable mix, but we can't find solid dependable advice. Maybe some of you could help?

So far, we've come up with a mix of fireclay, perlite (for insulation purposes) and a refractory cement. We need a chamber that is 2-3" thick.

The mix ratio I've come up with so far is 1:1 and a bit ? of refractory cement with just enough water to keep the mix together but a mix that breaks apart with a "pop" when squeezed together between your fingers.

If we use this refractory cement (or mortar) any idea of the mix ratio? Some say "as much as we can afford" but that isn't much help.

Is there any reason we can't use Portland cement instead of the refractory cement?

Yes, Portland quickly degrades from thermal cycling and will not last long.

We understand the mix needs to be gradually heated to prevent excessive cracking. None of the mix will be seen - the resulting castings will all be hidden by metal.

The castable will get some abuse from the wood fuel being fed into the stove, but nothing significant. So, some abrasive wear is to be expected.

Bottom line is we need a low cost durable castable mix we can produce with consistency.

I think your best bet is to experiment with your own mix designs using material with refractory properties

My family comes from a long line of masons from Europe dating back several centuries, but none of my ancestors who could provide the answers are alive today.

Ours is a start-up business and we hope to produce these stoves commercially. Any help / advice /suggestions some of you experts would care to give would be most appreciated.

Thanks in advance.

Some people have made ovens using 3:1:1:1 ratio with sand,lime,fireclay, and portland and have been successful. But if this application is for a commercial business, then you should think twice...and, no disrespect to the forum.....what you are asking is beyond causal builder/user knowledge base. Fire mortar and refractory are two different things, and I doubt you should trust any "homebrew" design without engineering and testing before incorporating it into your product.

[RocketStoveBuilder]

I hope you don't mind my asking for advice for non-oven related uses, but many of you most likely have the correct and accurate information needed. This forum seems like the best place to get solid advice about what kind of "home brew" mix to use for a 1500* F burn chamber and heat riser (chimney) for our rocket stove mass heaters:

We've built our stoves with fire bricks and 8" chimney flues - and they work fine. We also wrap our stoves with metal so they basically look like a woodstove as you can see in the above image.

The problem is, using these bricks and flues requires too much metal and too many welds resulting in higher labor and material costs; hence we want to build these two components - the burn chamber and burn riser (chimney) from a mixed (refractory) castable.

Pre-mixed commercially available materials - such as Sparlite 80 - are expensive as is the shipping.

We'd much prefer to create our own "home brew" castable mix, but we can't find solid dependable advice. Maybe some of you could help?

So far, we've come up with a mix of fireclay, perlite (for insulation purposes) and a refractory cement. We need a chamber that is 2-3" thick.

The mix ratio I've come up with so far is 1:1 and a bit ? of refractory cement with just enough water to keep the mix together but a mix that breaks apart with a "pop" when squeezed together between your fingers.

If we use this refractory cement (or mortar) any idea of the mix ratio? Some say "as much as we can afford" but that isn't much help.

Is there any reason we can't use Portland cement instead of the refractory cement?

We understand the mix needs to be gradually heated to prevent excessive cracking. None of the mix will be seen - the resulting castings will all be hidden by metal.

The castable will get some abuse from the wood fuel being fed into the stove, but nothing significant. So, some abrasive wear is to be expected.

Bottom line is we need a low cost durable castable mix we can produce with consistency.

My family comes from a long line of masons from Europe dating back several centuries, but none of my ancestors who could provide the answers are alive today.

Ours is a start-up business and we hope to produce these stoves commercially. Any help / advice /suggestions some of you experts would care to give would be most appreciated.

Thanks in advance.