Additives for refractory cement?

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warno

Minister of Fire
Jan 3, 2015
1,237
illinois
Since refractory castable cement is so expensive I was wondering if there is any additives I could use along with the refractory for my fire box lining. I read about people using fire clay or other cements mixed into it but I don't know how that would hold up. Basically I'm trying to get 10 pounds of stuff out of a 5 pound bag. Just trying to strech 50 pounds of refractory as far as possible with cheaper add-ins. Could anyone help me out here?
 
If you are taking your old lining out to replace it you might try pulverizing the old lining bits as finely as possible and mixing that into the new mix.
This is commonly done with stoneware clay for pottery work. Helps keep the clay from shrinking so much when it is fired. Less likely to crack.
Might be worth experimenting with on a small scale first if you have the time.
 
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This will all be new lining. It's for my boiler I'm building. So I'm looking for things I could add to new refractory.

I wad wondering about high temp mortar or would that not be good? Or is there a difference between the 2 at all?
 
You could get some fire brick new or used and crush it up. It can be bought fairly cheap and if someone is tearing down an old house or building, some might be salvaged. Put a ad on Craigslist for old or used fire bricks. Someone should have something and if they are in good enough shape maybe just use the fire brick in some places.
 
. Basically I'm trying to get 10 pounds of stuff out of a 5 pound bag. Just trying to strech 50 pounds of refractory as far as possible with cheaper add-ins. Could anyone help me out here?

I would not consider adding any foreign material to your castable refractory mix. The instructions on the bucket or bag usually tell you not to mix just a portion but to mix the entire bag at once, as mixing just a portion the ratios may not be correct due to settling of the different additives in shipment.

To be sure you are going to have enough volume, calculate the cubic inches needed against the suggested volume of the bag.

Sometimes stainless steel needles are added at a ratio of 2.5% of the volume of the mix to give the refractory added strength.

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I did get some of those needles to add in. I think my 100 pounds I ordered should be enough for everything.
 
If you don't mind me asking,where did you buy the refractory cement from?
I'd like to find a source in Canada
Thomas
 
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