recipies for refractory cement?

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  #1  
Old 05-17-06, 12:49 AM
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recipies for refractory cement?

anybody know a recipie for refractory cement?
 
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Old 05-17-06, 03:28 AM
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There is no recipe for refractory cement that can be mixed by hand. You can use fire clay with a small amount of portland cement mixed in, but that is a poor substitute for refractory cement.
 
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Old 05-17-06, 11:50 PM
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i found the following recipie on this site:

http://www.traditionaloven.com/tutorials/concrete.html

River gravel or crushed fire bricks
Sand
Calcium Aluminate cement. (if available in different grades choose the better one)
Lime (lime is usually cheaper, about 80% of the cement price)
Water
You can add into this mix a little standard Fireclay if you like.

Mixture: (parts ratio is 3 x 2 x 2 x 0.5, plus water)
3 shovels of the gravel or crushed firebricks
2 shovels of sand
2 shovels of the cement
half shovel of lime
This amount will require approximately 6-7 liters of water to mix the concrete.


i also found out that there is alumina cement and portland cement. the alumina cement is sometimes called fondue, which was the first company to produce and sell it. there was a big craze about it at the beging of the century because it achieves much higher strength than portland sement in a short time. it has the same strength as portland cement in 24 hours as portland has in 28 days. but, the catch is that its strength degrades quickly. but it has very nice refractory properties. the more alumina the better for heat resistance.
 
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Old 05-18-06, 04:35 PM
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The idea behind refractory cement is not the same as it is for mortar between bricks. Refractory cement is used only to chink the gaps between firebrick. There should be no mortar joint, and as little refractory cement as is possible should be used. In regular masonry, the mortar is the matrix that binds the masonry units together, but using a refractory cement is only to ensure a solid face to the flame.

A pre-mixed refractory cement will have bonding adhesion, however, and that alone makes it's cost worthwhile. Fire clay (the formula above) has no strength, no adhesion properties, and is a PIA to work with.

However, if you are determined to use it, this is how to do so:

Put your fireclay in a 5 gallon bucket. Gently fill the bucket with water, but DO NOT stir it. Let the material sit for at least 24 hours, and pour off the excess water. Gently stir the material for consistency. To use, dip each fire brick into the bucket and scrape off the excess on each face that it is not required before you lay the brick. Keep the joints as thin as is possible, as in non-existent.
 
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Old 05-19-06, 01:10 PM
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tscarborough,
would you use the same fire clay technique you describe with the lime/alumina cement mixture?

i wanted to find a cheaper alternative to building a wood burning oven than buying a bunch of fire bricks. would it be insane to use that cement mixture and pour the primary insulation layer of the oven with it?
 
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Old 05-19-06, 02:35 PM
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No. Fireclay has no strength and can not be used as refractory coating alone. You can parge smoke chambers with it, but that is about it. The only other option than firebrick is castable refractory, but I think you will find that to be more expensive than buying the fire brick.
 
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Old 05-19-06, 02:50 PM
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so the recipie above with alumina cement , lime , rocks and a little fire clay WOULD NOT work as castable refractory? why not?
 
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Old 05-19-06, 03:05 PM
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No structural strength.
 
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Old 05-19-06, 03:19 PM
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since it'd just be the cooking hearth and the dome, it doesn't need to support much weight - would the lack of structural strenght matter in that case?

by the way, thank you very much for your correspondance on this, i've been looking for answers on this for quite a while.
much appreciated.

max
 
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Old 05-19-06, 05:07 PM
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If you use it as a coating (parging), it could work, but since it costs as much or more than fire brick and has such poor performance, why would you bother?

Regular firebrick should cost about a buck each, giving a sqft cost of 4.50$ or less, and will last for hundreds of years under most conditions. Why not do it right?
 
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Old 05-20-06, 07:40 AM
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Refractory cement

An HVAC or plumbing supply house, particularly one which deals in commercial boilers, should have refractory cement. It comes in containers, pre-mixed, ranging in size from a couple of pounds to 100#.
 
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Old 05-20-06, 12:33 PM
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recipies for refractory cement?

If you are going to use refractory cement as a thick coating or a cast product that will be outdoors, pay particular attention to the aggregate used. This is if you are going to the very high temperatures that justify the trouble and expense of re-inventing the traditional ovens.

The refractory is not an insulating layer.

I used refractory cement in the 1960's to protect rock from the errosion caused by rocket engines and cooling water.

This was natural rock covered by gunite applied fondue type or lumnite-based concrete mix. This was a high desert climate (hot days, cold nights). Because of the non-continuous use there were some problems.

It performed quite well, but there was constant maintenance because of differential absoption and othe properties of the cement paste and the rock or aggregate.

Your fondue oven ideas could work, but why try to do it different than what works and is proven? There are brick kilns (beehive and rectangular, continuous) all around the world that perform quite well without the fine fire brick we have access to at a low cost. They use fire brick in rotary kilns more many processes.

You must be anticipating some very unusual temperatures and conditions.

Dick
 
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Old 05-20-06, 09:50 PM
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thanks guys,
my only objective in this was to save money. i figured mixing the refractory concrete my self would be cheaper than the fire brick, which i can't really find for cheap. maybe 2$ each.

dick, what are these ovens from arround the world you describe made out of if not fire brick or refractory cement? i thought regular brick would break in the hot temperatures of an oven.
 
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