# refractory cement



## yonderfishin (May 15, 2012)

A guy at the brick store I called said all I would need to make basic refractory cement is fire clay and refractory mortar , and it should work for use in a simple small charcoal foundary/furnace. Can anybody on here who has built one before verify that this will work right ? Ive seen where people put some other other additives in it but Im hoping its not necessary due to cost.


I have a small galvanized trash can with lid to line the inside with the cement and am planning to put a steel pipe through near the bottom at the charcoal and use a hair dryer for a blower. From what Ive read that "should" ( hopefully) get hot enough for smelting black sand and pyrite. The other question is do you think this will work for what I want to do with it ?


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## martyn111 (May 15, 2012)

I haven't actually built a furnace/foundry but there is plenty of information and tips available on a site regularly mentioned on this forum, for building such equipment on a budget, see the link below

http://www.backyardmetalcasting.com/index.html


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## Geo (May 15, 2012)

fire clay, refractory cement and pure silica sand. make sure the sand is the right kind. im sure silica sand can be obtained cheaply.


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## gold4mike (May 18, 2012)

I'm not at home right now so I don't have the bag in front of me but I use "Play Sand" from Lowe's to distribute the heat under my beakers and I believe it's Silica Sand.

As Geo said, it is very cheap.


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## Harold_V (May 19, 2012)

Because of the hazards of silica, I expect that the sand in question (play sand) isn't silica, but I could be wrong. 
Silica sand is readily available from concrete supply houses. It's sold in 100 pound bags, for under $10/bag. It comes classified, with numbers like 70, 30 and coarser (don't recall the numbers). Do handle it with care, as the dust is quite hazardous. No fear of melting, as silica melts at over 3,000°F. 

Harold


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## yonderfishin (May 20, 2012)

The next one I build I will get better sand but this time around I just used some quikrete all purpose sand I already had and it worked good , held up well to the initial firing which I let get good and hot. There was a warning on the bag that it contained silica so I should be atleast partially covered. As to how well it conducts heat and how long it will last I dont know. I will no doubt make another one anyway since I learned a lot in the construction of this one. The other components of the cement are a bag of fire clay and a bag of type N masonry mortar. It didnt harden as well as I thought it would but it got considerably harder after firing it good and hot. As always , thanks for the help.


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## goldpete (Jul 6, 2012)

yonderfishin said:


> A guy at the brick store I called said all I would need to make basic refractory cement is fire clay and refractory mortar , and it should work for use in a simple small charcoal foundary/furnace. Can anybody on here who has built one before verify that this will work right ? Ive seen where people put some other other additives in it but Im hoping its not necessary due to cost.
> 
> 
> I have a small galvanized trash can with lid to line the inside with the cement and am planning to put a steel pipe through near the bottom at the charcoal and use a hair dryer for a blower. From what Ive read that "should" ( hopefully) get hot enough for smelting black sand and pyrite. The other question is do you think this will work for what I want to do with it ?



thats exactly howi built mine but cement alone wont take the heat . you will need to mix perlite with the sand and cement. that will serve two functions . one , it will give insulation to the mix when your using it and two , it will make it much lighter to move around.


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## donnybrook (Jul 13, 2012)

Castables for furnace building are ready made and are not that expensive. I use 1600 c (not sure of the conversion to farenheit over there). I have used just fire clay as a mortar for brick bonding. Its sold in farming produce stores here and is used for such things as sealing dams on farms. Its in a dry powder form. You can also use fire clay with an amount of aggregate to ram a furnace. Getting the so called whinge and wine mix right is the key to success as is the proper curing. There are sites on the web that give other recipies. As you know you cannot use ordinary cement.

donnybrook


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## publius (Jul 14, 2012)

No need to use cement. 20% fire clay, 80% sand, enough water to pack it tight. http://www.lindsaybks.com/dgjp/djgbk/char/index.html Dave Gingerly has a great book on the charcoal foundry... :lol:


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## Harold_V (Jul 14, 2012)

donnybrook said:


> (not sure of the conversion to farenheit over there).


9/5C+32=F (1600°C=2912°F)

Harold


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## pugle1 (Oct 17, 2012)

For my aluminum furnace I used a mix of dried cement sand (standard brick mortar sand), portland cement, fire clay and a large quantity of pearlite from a garden center. Mix with water as with regular brick mortar, but to a slightly drier consistency. When you pack it into what will be your furnace, pack it well ( make sure there are no air pockets). Let it cure for 2 weeks, then set a "cool" fire in it to cure it. On your first firing, start slow, and let the temp build-up gradually. Do not have a melt loaded for the first firing. After an hour or so at a low heat, slowly increase the temp up to its max operating temp. Leave it there for 10 minutes or so, then reduce the heat slowly until you finally just let it cool on its own.

**edit: If it's going to fail, it will fail here.**

My first crucible was a medium gauge stainless steel container, and the furnace was fired with BBQ briquettes (partially crushed) and forced air. On the third firing with a load of aluminum in the crucible, the crucible melted. I now use a very heavy gauge stainless steel crucible which is holding up so far ( 40 to 50 melts) and the refractory is still going strong. There's a little bit of pitting and erosion, and a little bit of glazing.. but so far, there seems to be no need to replace the lining. I also made plinths out of the same material. They're good for several uses, but eventually melt into a black glass-like substance and become deformed needing to be replaced.


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