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  #41  
Old 11-02-2013, 01:25 PM
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Default Re: Your Advice Re: HomeBrew Castable Mix Greatly Appreciated

The calcium aluminate cement only requires 24 hrs curing, it does not continue to increase strength over time like Portland cement. It is advisable to cover it to hold it the moisture while curing though.

I think your cracked brick is almost certainly caused by temperature difference of which there will be plenty in a rocket stove. It wouldn't matter how high the quality of your fire bricks are they will still crack if the temperature difference and hence the expansion is too great. The only remedy here is to heat them slowly to allow the temperature and expansion to even out and this is not really an option. Either live with the cracks or engineer joins where the cracks were.

Last edited by david s; 11-02-2013 at 01:31 PM.
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  #42  
Old 11-02-2013, 05:43 PM
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Default Re: Your Advice Re: HomeBrew Castable Mix Greatly Appreciated

"I hope you continue updating your progress..this is very interesting. As to your test brick, perhaps the mix needed more hydration..after all not enough water in the mix is as bad as too much."

We made two test 1 1/4" bricks - one with more water - but didn't cut that brick. Will check Monday. I've been told too much water is not good either - so don't know what to make of it. Maybe we heated them too soon......

We also made a 4" thick brick. Will check it Monday also.

"Either live with the cracks or engineer joins where the cracks were. "
We can live with the cracks as they are not that significant.

thank you both for your interest.
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  #43  
Old 11-06-2013, 05:40 AM
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Default Re: Your Advice Re: HomeBrew Castable Mix Greatly Appreciated

Put the "home brewed" brick inside the rsmh yesterday right where the fire burned most of the day. This was after we had the bricks set on the stove itself to cure for two days. Checked it last night - didn't seem to be any damage.

We also put another home brewed brick, one with more water added to the mix, deep inside the stove right below the burn riser (chimney). Will remove and check today.

We place our 4" brick on top of the stove on the hottest part of the metal - between the fuel feed and the outer shell for the last two burns. Checked the temperature of the brick - at times the brick was close to 500* F. No signs of damage.

With the cost of commercial refractory castables for each individual stove priced at $550, (including shipping - shipping is expensive isn't it?) we are going to proceed with our stoves using our own mix and continue testing as we go. We cannot justify spending over 25% of the cost of the stove on these components of the rs when we believe we can make these components ourselves in house with our own mix with satisfactory results.

As promised, I will post images as time allows. Thanks for your input and suggestions.
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  #44  
Old 11-06-2013, 06:22 AM
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Default Re: Your Advice Re: HomeBrew Castable Mix Greatly Appreciated

Quote:
Originally Posted by michelevit View Post
...... The refractory manufactures are in the business of manufacturing and selling
refractory. I already know the answer they will give me.

I have proven that the homebrew does work as a refractory casting material. Why is everyone so adamant that it wont work? It does work. Its is what is used to hold a traditional brick oven together.
What are your opinions to using a portion of Portland cement along with alumina cement in our mix? Not much - but enough to aid in the binding.

Are there any advantages, disadvantages?

I understand Pcement needs time to cure, but that really isn't a factor in our case.

Any comments welcomed and appreciated.
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  #45  
Old 11-06-2013, 07:21 AM
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Default Re: Your Advice Re: HomeBrew Castable Mix Greatly Appreciated

Quote:
Originally Posted by RocketStoveBuilder View Post
What are your opinions to using a portion of Portland cement along with alumina cement in our mix? Not much - but enough to aid in the binding.

Are there any advantages, disadvantages?

I understand Pcement needs time to cure, but that really isn't a factor in our case.

Any comments welcomed and appreciated.
The thing is, a lot of refractory cements and castables are made with a small percentage of portland in it. But it is understood that the more portland in the mix design, the weaker it will at sustained high temperatures. What you should consider doing, is developing a mix with different levels of portland, but at very low percentages.

That is the issue with using 3:1:1:1, the portland ratio is very high...and to avoid repetition, that's all I will say about that.

I also believe that one or two test fires are not sufficient to determine a quality product....but that is an opinion and ideology, and everybody is different. Take that with a grain.....
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  #46  
Old 11-06-2013, 01:20 PM
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Default Re: Your Advice Re: HomeBrew Castable Mix Greatly Appreciated

As a aside...I have found out that the cf board is and has been used for risers....with and without the ridgidizer with great sucess..... May help with weight if shipping once you get a casting mix. heat riser | Rocket Stoves.. Experimenters corner.. Answers questioned! Perhaps you should ask the casting mixture question there....
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  #47  
Old 11-07-2013, 07:02 AM
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Default Re: Your Advice Re: HomeBrew Castable Mix Greatly Appreciated

Quote:
Originally Posted by stonecutter View Post
I also believe that one or two test fires are not sufficient to determine a quality product....but that is an opinion and ideology, and everybody is different. Take that with a grain.....
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?

"May help with weight if shipping once you get a casting mix. heat riser | Rocket Stoves.. Experimenters corner.. Answers questioned! Perhaps you should ask the casting mixture question there.... "

I have.

And yes, we like the idea of using the board, again it is a question of cost. 2" ceramic fiber board sells for about $20 a square foot making just the riser in our stove over $200 plus we need the adhesive to hold them together at more cost. For now, we'll cast our own and then use the board aftger we make a few sales. This is virtually a new industry so we'll keep testing.
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  #48  
Old 11-07-2013, 07:50 AM
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Default Re: Your Advice Re: HomeBrew Castable Mix Greatly Appreciated

Quote:
Originally Posted by RocketStoveBuilder View Post
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.
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  #49  
Old 11-07-2013, 08:23 AM
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Default 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.
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  #50  
Old 11-07-2013, 08:49 AM
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Default 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.
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