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  #11  
Old 08-05-2011, 06:09 AM
Serf
 
Join Date: Aug 2011
Location: Australia
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Default Re: Vermiculite+portland cement to make fire bricks? What is fire clay?

Yeah that is pretty much what I found in the net. YOu can use 0.8mm but it is not as effective as the 0.5mm. They call 0.5mm premium and 0.8mm economy. More fibres wiht the smaller diameter.

Anyway I will definantly now be using some of my 0.9mm stainless wire. Hey, it's gotta do something, better than not having it.

Have you ever used from claypave Rylbond mortar (1450). Would be nice to use this for say 20mm wall thickness. It says it air drys but is only a cement for small thin applications.

Surely there is a product that I can just use to make a 20mm thick or what ever thick wall with out it cracking, or needing to be fired properly in an oven?

And if I used fire bricks are they easy to cut?
Can you tie them together?
I have a price list from claypave but I don't know if they are for insulation type fire bricks or for themal heat holding type bricks.
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  #12  
Old 08-05-2011, 12:37 PM
Journeyman
 
Join Date: Aug 2010
Location: Glendale, Arizona
Posts: 394
Default Re: Vermiculite+portland cement to make fire bricks? What is fire clay?

Hi All,

I have one of the Aprovechio rocket stoves that I bought at a store that sells preparedness supplies. They have canned, dehydrated foods and solar ovens too.

You Tube has lots of information on rocket stoves and you can Google for information too. Mine is made of refractory clay but you can make a rocket stove of nothing more than stacked fire bricks or red bricks. Sometimes a temporary stove made of stacked bricks is efficient and economical depending on the needs of the moment.

If you plan on using a small rocket stove then maybe making the hot face from Raku clay would work ok. It is strong and easily available from a ceramics shop. Also consider "paper clay" it has cellulose fibers in it and it also can be fired at low temperatures compared to other types of clay. You can insulate around the "chimney" with a variety of things including wood ash, ceramic blanket, vermiculite and perlite. Mix up some vermicrete or perlcrete for a top layer, install bolts or pieces of rebar for the pot to stand on and you're in business.

Cheers,
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  #13  
Old 08-05-2011, 01:21 PM
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Location: Townsville, Nth Queensland,Australia
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Default Re: Vermiculite+portland cement to make fire bricks? What is fire clay?

"Surely there is a product that I can just use to make a 20mm thick or what ever thick wall with out it cracking, or needing to be fired properly in an oven?"

I was planning on using a dense castable (Caldreys Castflo 1450) and mixing about 25% perlite into it, then outside that using 2" perlcrete 10:1 then outside that a 10mm ferrocement outer shell.
But there are many ways it could be done, just depends what you have access to.If you know anyone with a kiln you could design it in pieces and have them fired.

Last edited by david s; 08-05-2011 at 01:23 PM.
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Old 08-05-2011, 03:09 PM
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Default Re: Vermiculite+portland cement to make fire bricks? What is fire clay?

Hi David s,

Calderys website lists no less than sixteen "dense" castables and five insulating castables. Is there a reason you would mix insulating perlite with a dense castable? It seems the castable would be much more resilient and long lasting without an admix of insulation.

Apples,

Cracking is not an issue with the rocket stove. If it can be made with stacked bricks with their inherent spaces between then a crack in the chamber is nothing to worry about. Also, I am not sure that a clay chimney needs to be fired "properly" in a kiln since the example I saw was simply dried completely then heated using a wood fire. In this example the level of firing from the wood was adequate to harden the clay for its intended use as a fire chamber for a stove. Ideally though, if you have access to a kiln then you can be assured it was done professionally. However, for the cost of raw materials involved I'd go with doing it yourself. You can even fire clay the old fashioned way by putting the piece in a fire pit. Look here:

Pit fired pottery - Wikipedia, the free encyclopedia

Claystation Technical

Cheers,
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  #15  
Old 08-05-2011, 03:39 PM
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Default Re: Vermiculite+portland cement to make fire bricks? What is fire clay?

[QUOTE=azpizzanut;118550]Hi David s,

"Calderys website lists no less than sixteen "dense" castables and five insulating castables. Is there a reason you would mix insulating perlite with a dense castable? It seems the castable would be much more resilient and long lasting without an admix for a stove."

I agree, but you don't really need that thermal mass for a rocket stove, that's why I was intending only adding a relatively small proportion of perlite so the mass is reduced while the strength not too compromised. Another reason I was planning on using the dense castable and "adjusting" it is because I have it on hand and use it all the time.

Last edited by david s; 08-05-2011 at 04:15 PM.
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  #16  
Old 08-05-2011, 03:50 PM
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Default Re: Vermiculite+portland cement to make fire bricks? What is fire clay?

"Cracking is not an issue with the rocket stove. If it can be made with stacked bricks with their inherent spaces between then a crack in the chamber is nothing to worry about. Also, I am not sure that a clay chimney needs to be fired "properly" in a kiln since the example I saw was simply dried completely then heated using a wood fire. In this example the level of firing from the wood was adequate to harden the clay for its intended use as a fire chamber for a stove. Ideally though, if you have access to a kiln then you can be assured it was done professionally. However, for the cost of raw materials involved I'd go with doing it yourself. You can even fire clay the old fashioned way by putting the piece in a fire pit."

Bob,
Clay which is unfired can turn back into mud if it gets wet. it needs to be fired to 573 C before it becomes permanent and you'll never get it that hot in the chimney alone. You can try doing it yourself in a campfire or sawdust kiln, but it is tricky and prone to blowing and cracks as well as being not fired particularly high enough (typically a sawdust firing will be in the region of 600C) to make it sufficiently hard and durable. Should be taken to over 1000C IMO This would require a kiln. Using a castable means you don't have to fire it, although ideally even a castable is better if it is fired first.

Dave

Last edited by david s; 08-05-2011 at 04:16 PM.
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  #17  
Old 08-05-2011, 04:50 PM
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Default Re: Vermiculite+portland cement to make fire bricks? What is fire clay?

Hi David s,

Thanks for the clarification. Yeah, that sounds reasonable. Whatever works by experience is often successful enough. I agree, castable is the way to go. The other options will work too if you are mindful of their individual requirements.

I like the part about turning back into mud if it gets wet. Lesson learned the hard way.

Cheers,
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  #18  
Old 01-13-2013, 01:14 AM
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Join Date: Jan 2013
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Default Re: Vermiculite+portland cement to make fire bricks? What is fire clay?

Hi guys, am new here. Am sort of an expert when it comes to what you guys call rocket stoves.
A simple explanation on how to make a rocket stove is to use a steel cylinder of light gauge with a fire door at the very bottom and a chimney near the top on the opposite side of the door, on the side. The cooking pot should fit loosely inside the cylinder (leaving enough space for hot gases and smoke to flow) but completely cover the top (so that smoke will travel out through the chimney on the side).
Now to come to your dilemma - insulation. The inner part of the cylinder is lined with a wall of clay bricks to give it strength to hold the weight of the pot. For insulation we use vermiculite mixed with terrazzo chips, a little clay and refractory cement.
We call these types of stoves "energy saving stoves". No wires or nails are necessary. Contact me for a simple drawing of such a stove and pictures.
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