Your Advice Re: HomeBrew Castable Mix Greatly Appreciated

[david s]

Re: Your Advice Re: HomeBrew Castable Mix Greatly Appreciated

Thanks for the info David!

Too bad about the CSA isn't it? I wonder why CA cement is so much more expensive?

What do you think about the inclusion of potassium silicate as an admixture in a refractory mix? This is sold as a surface densifier, but it is also used to seal radiator leaks and reportedly is an ingredient in refractory materials, at least according to Wikipedia. "Water glass" is another old term for it.

I've also wondered how well lime mortar (straight lime) holds up to heat. My guess is that it is a poor refractory, but I'm sure someone here has a more official answer to this question. I understand that before the invention of Portland cement, lime putty mortar was the only game in town, so it must have been used to build fireboxes and ovens at some point.

Yes it is a pity about CSA. I think it is a major ingredient used in rapid set concrete. I don't know about the use of potassium silicate in refractory. I use a bit of sodium silicate as a deflocculant in making clay slip, it has many other uses too. The "home-brew you may see mentioned frequently on this site which is 3:1:1:1 sand, Portland cement, clay, lime makes an excellent refractory mortar which works extremely well for a WFO temperature range and can also be used as a castable mix, although probably not as good as a proprietary CA cement based castable.

[Killian]

Re: Your Advice Re: HomeBrew Castable Mix Greatly Appreciated

Thanks for the info David!

Too bad about the CSA isn't it? I wonder why CA cement is so much more expensive?

What do you think about the inclusion of potassium silicate as an admixture in a refractory mix? This is sold as a surface densifier, but it is also used to seal radiator leaks and reportedly is an ingredient in refractory materials, at least according to Wikipedia. "Water glass" is another old term for it.

I've also wondered how well lime mortar (straight lime) holds up to heat. My guess is that it is a poor refractory, but I'm sure someone here has a more official answer to this question. I understand that before the invention of Portland cement, lime putty mortar was the only game in town, so it must have been used to build fireboxes and ovens at some point.

[david s]

Re: Your Advice Re: HomeBrew Castable Mix Greatly Appreciated

Calcium sulfoaluminate (CSA) cement is not the same as calcium aluminate cement (CA). The CSA loses around half it's strength when heated to around 300 C, so I don't think it would be suitable. Stick with CA cement, but by all means give it a shot and report back. It may be better than the portland and lime homebrew.
Here's a good reference.

http://www.cementchina.net/web/uploa...2794825313.PDF

[Killian]

Re: Your Advice Re: HomeBrew Castable Mix Greatly Appreciated

Hey all!

Has anyone tested CSA (calcium sulfoaluminate) cements in a high-heat situation? This type of cement is available at the Home Depot under the name "Cement-All"- the bagged mix contain about 50-50 cement/aggregate, plus "air" (unless you are in California) and a low-range superplasticizing agent. Possible other things.
Pure CSA can be ordered from most concrete countertop suppliers.
Also, why not add pozzolans to the homebrew mix- fly ash, silica fume, metakaolin, etc? Probably could add some strength.
I also happen to have on hand hydrous potassium silicate, also known as "water glass". This is used in refractory applications, such as sealing radiators and hot water pipes- the silicate precipitates and is slightly expansive at high temperatures. From what I heard, anyway. 5 gallons costs less than $50.
I haven't tested this mix yet, but the following might yield a slightly more durable homebrew castable refractory- not suitable for rocket stoves, kilns, or the like, but possibly good enough for a pizza oven:
3 sand
1 pea gravel (larger aggregate size gives higher compressive strength)
1 fireclay
1/2 cementitious

The cementitious consists of 80% OPC, 10% silica fume, and 10% CSA. Too much CSA and the mix will set too fast for most people's comfort level.

I would mix the wet ingredients at 20% potassium silicate to 80% water...

Maybe I'll test it sometime...

I made my oven in the usual way from firebricks, using fireclay/portland mortar, and it's holding up great! I am curious about castable ovens because I think it would be fun to make a little one that could heat up faster and possibly be portable. Also, pretty darn easy and cheap. Why not?

[david s]

Re: Your Advice Re: HomeBrew Castable Mix Greatly Appreciated

For an oven you want a strong dense mix, not an insulating one, so don't add perlite. The rocket stove application is different.

[RocketStoveBuilder]

Re: Your Advice Re: HomeBrew Castable Mix Greatly Appreciated

RocketStoveBuilder, What is your mix?

1:1:1 Fireclay, perlite, fine sand (30/40).

Dry mix.

Add.

3/4 Rutland 211 Refractory mortar. (any similar refractory cement/mortar should work.)

Dry mix.

Start with 3/4 water and check for consistency. After several castings we tend to think more water is better, but the drying time and the slower burn in process takes longer.

This has been working for us. Hope it helps.

[david s]

Re: Your Advice Re: HomeBrew Castable Mix Greatly Appreciated

michelevit made a brickless oven on a shoestring (see the thread with that title) using the homebrew mix of 3:1:1:1 of sand, clay, lime and Portland cement.
Look further back in this thread, and you will see he is adamant that it works and is robust.
If you make sure it has fully dried and heat it very gently at first, giving any water a chance to migrate out slowly, it should not explode.

Add polypropylene fibres to assist in safer water removal. They melt and burn away leaving a network of tiny pipes that steam can escape through.

[kira]

Re: Your Advice Re: HomeBrew Castable Mix Greatly Appreciated

thank you michelevit, does anyone know anything about Reno Bond 3000? Ive been told it can be used to cast an oven... Thanks!

[wotavidone]

Re: Your Advice Re: HomeBrew Castable Mix Greatly Appreciated

RocketStoveBuilder, What is your mix? I am wanting to cast a dome out of a homebrew, have heard a few times it works, but am concerned with an explosion...lol... I'd really appreciate your help on gettingthis mix right as I too am a starting a small business (not rocket stoves) and can not afford to invest in a ton of commerical grade refractory cement. All I want to do is build one oven!! Please and thank you.

Ps Love your persistance and bravery!

michelevit made a brickless oven on a shoestring (see the thread with that title) using the homebrew mix of 3:1:1:1 of sand, clay, lime and Portland cement.
Look further back in this thread, and you will see he is adamant that it works and is robust.
If you make sure it has fully dried and heat it very gently at first, giving any water a chance to migrate out slowly, it should not explode.

[kira]

Re: Your Advice Re: HomeBrew Castable Mix Greatly Appreciated

"So you are going to use 3:1:1:1 for commercial production based off a test fire and a one off recommendation, in spite of what is understood about Portland ratios industry wide???? I hope you have a good warranty policy....I'm done with this."


We are not using Portland cement in our mix.

RocketStoveBuilder, What is your mix? I am wanting to cast a dome out of a homebrew, have heard a few times it works, but am concerned with an explosion...lol... I'd really appreciate your help on gettingthis mix right as I too am a starting a small business (not rocket stoves) and can not afford to invest in a ton of commerical grade refractory cement. All I want to do is build one oven!! Please and thank you.

Ps Love your persistance and bravery!

[stonecutter]

Re: Your Advice Re: HomeBrew Castable Mix Greatly Appreciated

We are not using Portland cement in our mix.

That is a wise move. I wish you well on your mix design, and your venture.

[RocketStoveBuilder]

Re: Your Advice Re: HomeBrew Castable Mix Greatly Appreciated

$8.48 per SqFt here: Ceramic Fiber Board

And much cheaper in bulk, I am sure.

Thanks! Checking now.

[RocketStoveBuilder]

Re: Your Advice Re: HomeBrew Castable Mix Greatly Appreciated

"So you are going to use 3:1:1:1 for commercial production based off a test fire and a one off recommendation, in spite of what is understood about Portland ratios industry wide???? I hope you have a good warranty policy....I'm done with this."


We are not using Portland cement in our mix.

[Tscarborough]

Re: Your Advice Re: HomeBrew Castable Mix Greatly Appreciated

$8.48 per SqFt here: Ceramic Fiber Board

And much cheaper in bulk, I am sure.

[stonecutter]

Re: Your Advice Re: HomeBrew Castable Mix Greatly Appreciated

We used a mix that was recommended by someone who said it was working fine for them for quite awhile. Another day in the fire yesterday, no cracks detected. With even the commercial bricks with fine cracks developing, how bad can our mix be?

So you are going to use 3:1:1:1 for commercial production based off a test fire and a one off recommendation, in spite of what is understood about Portland ratios industry wide???? I hope you have a good warranty policy....I'm done with this.