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Mortar
Jul 31, 2018 11:15:35 GMT -8
Post by bryani on Jul 31, 2018 11:15:35 GMT -8
Sorry to create a new thread but I can find many mentions of mortar on the board but stand (again) a little confused. I found a thread which Peterberg says 1:1 clay sand will work for a test stove and I am using that in mine. I have used Donkeys recipe of clay, sand, ash for making up half bricks for use in my test stove. He also says it can be used as mortar. I have seen Matt Walker talk about a recipe using purchased Fireclay. Other threads have said that the clay sand mortar fails and that refractory mortar should be used I'm left scratching my head. Can anyone direct me to a recipe for a proven mortar which I can use on the stove I build inside my house - again I'm sorry for my confusion I'm trying to get it right and am a senior with not a lot of time for experimentation I will say that I have lots of clay around here and am pleased if that is the key ingredient. Again - any help and direction most appreciated.
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Post by pinhead on Jul 31, 2018 11:23:39 GMT -8
In my stoves, the clay-sand-ash mortar has held up wonderfully between the bricks in the firebox and in the body of the bell.
As a monolithic form in the throat of a batch box, OTOH, it hasn't fared nearly as well.
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Post by Vortex on Jul 31, 2018 11:51:00 GMT -8
I think that's were a lot of the confusion comes from. Making a reliable homemade mortar for use in thin joints seems to be quite easy, but making a good reliable homemade castable refractory mix is a lot harder.
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Post by Dan (Upstate NY, USA) on Jul 31, 2018 15:45:58 GMT -8
Mortar in high temperature applications is not there to stick bricks together but to keep bricks apart.
What do I mean? Fire brick deforms when fired. So one side will be thicker than another etc. Imperfections.
Mortar evens these imperfections and ensures even weight loading brick to brick and side loading is even when the fire brick expands and contracts.
So if the "stickiness" of the mortar fails its not a big deal.
Even commercial mortar works the same is cracks and expands and fails to stick to the brick after several firings.
When homemade castable refractory mix fails the whole stove falls in.
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Post by Vortex on Aug 1, 2018 1:20:34 GMT -8
That's the danger with those tubs of 'Furnace Cement' that people seem to like using these days. It boasts of being 'stronger than the firebrick', which means there's no give for the expansion and contraction, so the bricks crack and they're so well stuck in you can't get them out to replace them.
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Mortar
Aug 1, 2018 10:40:00 GMT -8
Post by bryani on Aug 1, 2018 10:40:00 GMT -8
Thanks so much for replies and thoughts - it looks like for the finished stove senior members with a lot of experience go with clay/ash/sand mortar. Is the recipe used the same as Donkeys recipe on the board or some modification of it ? (http://donkey32.proboards.com/thread/850/mud-batch-box?page=2 )
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Mortar
Aug 1, 2018 17:00:09 GMT -8
Post by Dan (Upstate NY, USA) on Aug 1, 2018 17:00:09 GMT -8
I have used the pre-mixed wet furnace cement in the tubs. It is hard as hell, I have seen it stay together when the brick has already cracked from cyclic heat stress. Nice things about it is it dissolves with water after it has dried (At least the Heat Stop brand I find in America). Make a mistake or wanna make a change get it good and wet and it'll release.
I have used Powdered Heat Stop mortar too. That does not break down with water. It is suitable for outdoor stove that may get rained on. That stuff does not dissolve with water. Get it on a brick and try to reuse the brick and the brick can break in some places before the mortar will bust off. Fire it a couple of hundred times it comes right off the brick if you are recycling an old stove or project. But the brick will break in pieces too.
I have not used a clay ash sand mortar yet. But with a sound design I know I could make it work as well as the commercial stuff. Because I know that fire mortar serves and works in a different function/way than traditional brick mortar.
All three will work, a sound design that accounts for expansion and contraction is more important.
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Mortar
Aug 2, 2018 1:40:38 GMT -8
Post by woodrascal on Aug 2, 2018 1:40:38 GMT -8
Over here in the UK I've used various mixes for mortar in J tube and Batch Rockets and also a Brick Oven and Tandoor.
High Alumina cement worked well but is expensive and would often arrive from the builders merchants(when I could get it) already starting to go off in the bag. It sets very hard and doesn't seem to allow the bricks to expand/contract and has caused brick fracture as Wolf mentioned above.
The tubs of Furnace cement were easy to use but, on examination of my J Tube Rocket, have powdered and crumbled in high heat areas.
The most successful mix to date in my experience is a Fireclay/Sand/Portland cement mix. We know that the Portland cement can't cope with high heat conditions but it holds the clay/ together until that vitrifies when exposed to high temperatures.
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Mortar
Aug 26, 2018 17:05:23 GMT -8
Post by stephenson1 on Aug 26, 2018 17:05:23 GMT -8
Can anyone post some recipes?
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Mortar
Aug 30, 2018 21:37:30 GMT -8
Post by n8ivetxn on Aug 30, 2018 21:37:30 GMT -8
I don't have any experience with making mortar, nor the time to experiment with what works. I'm about to rebuild a unit I made last year, and I just bought a 50lb tub of super 32 from hti in portland or.
Last year, I used home depot's versabond stuff and I had some leaks that had to be patched over - several times. Since my unit is in a tropical greenhouse, the leaks didn't hurt much, but it sure was a pain trying to keep it all plugged up!
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Mortar
Nov 4, 2020 11:27:53 GMT -8
Post by Orange on Nov 4, 2020 11:27:53 GMT -8
Other threads have said that the clay sand mortar fails and that refractory mortar should be used I'm left scratching my head.
anyone has experience on clay vs fireclay?
I can only get "chamotte" powder which is a mix of fireclay and grounded red tiles and it's not sticky at all so it has to be mixed again with clay or waterglass.
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fuegos
Full Member
not out of the woods yet
Posts: 177
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Post by fuegos on Nov 4, 2020 11:46:21 GMT -8
When i had a Rayburn i used tubs of pre mixed "fireclay" from the builders merchants to do small repairs .It didn't last more than a season , cracking up pretty quickly , especially if it was thinly applied.Judging from the constancy , it was like putty , i didn't have any aggregate in it . Iv'e used clay iv'e dug out of the ground for my oven build & it's fine for laying bricks in a 3:1 sharp sand mix.The rule of thumb in building is that mortar shouldn't be stronger than the materials it is used with .
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Mortar
Nov 5, 2020 12:07:37 GMT -8
Post by hadydalaii on Nov 5, 2020 12:07:37 GMT -8
Sand/clay mortar works quite well for centuries. Though it can vary from 1:1 to 4:1 depending of how fat your particular clay is.
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