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Old 01-22-2013, 08:18 AM
dimitrisbizakis's Avatar
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Default Clay Mortar

Hi everyone, i was wondering, i have found an old factory that was making clay bricks.
I've got some bags from there and it contents is 98% clay and 2% silt.
I have already used this clay with 50% sand to make a dome for an cob oven.
Can i use this clay with fine sand and perhaps some lime as a mortar for building the dome?
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Old 01-22-2013, 12:54 PM
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Default Re: Clay Mortar

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Originally Posted by dimitrisbizakis View Post
Hi everyone, i was wondering, i have found an old factory that was making clay bricks.
I've got some bags from there and it contents is 98% clay and 2% silt.
I have already used this clay with 50% sand to make a dome for an cob oven.
Can i use this clay with fine sand and perhaps some lime as a mortar for building the dome?
Yes you can, but if the mix contains a high proportion of clay you will get shrinkage cracks. Use the home brew mix ie. 3:1:1:1 sand, cement, clay, lime. This mix works well and has proven to be a cheap and superior mortar for WFO's.
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Old 01-22-2013, 01:58 PM
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Default Re: Clay Mortar

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Originally Posted by david s View Post
Yes you can, but if the mix contains a high proportion of clay you will get shrinkage cracks. Use the home brew mix ie. 3:1:1:1 sand, cement, clay, lime. This mix works well and has proven to be a cheap and superior mortar for WFO's.
What's the difference of the clay i have found and the fire clay everyone says?
I mean, the clay i have is not a light gray but it can handle temp's up to 1000C (tested on a cob oven) so what is the worst scenario that can happen?
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Old 01-22-2013, 02:18 PM
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Default Re: Clay Mortar

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Originally Posted by dimitrisbizakis View Post
What's the difference of the clay i have found and the fire clay everyone says?
I mean, the clay i have is not a light gray but it can handle temp's up to 1000C (tested on a cob oven) so what is the worst scenario that can happen?
IMO pretty much any clay should be ok. (others may disagee) You only have about 16% by volume of clay in the mix anyhow. When firing in a WFO the temp only gets to around 500C at max.

Last edited by david s; 01-22-2013 at 02:21 PM.
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Old 01-23-2013, 04:27 AM
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Default Re: Clay Mortar

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Originally Posted by david s View Post
IMO pretty much any clay should be ok. (others may disagee) You only have about 16% by volume of clay in the mix anyhow. When firing in a WFO the temp only gets to around 500C at max.
Only at 500 "C"?
Are you sure?
What's the purpose of the clay in the mix?
The cement is Portland or refractory?

Last edited by dimitrisbizakis; 01-23-2013 at 04:37 AM.
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Old 01-23-2013, 08:56 AM
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Originally Posted by wotavidone View Post
He's sure. It's a pizza oven, it burns wood, there is no fan-forced air, no metallurgical coke or coal, no oxygen injection. In short, it's a wood fired oven, not a blast furnace
Unless you are using a draft door!
Right?
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Old 01-24-2013, 04:10 AM
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Default Re: Clay Mortar

Gudday
Disagree mick .like you said the refractory properties are really not required.
What you do get is a great mortar that's plastic,sticks to what is a really smooth surface easily, can handle lager gaps in the brickwork.I think the home brew mortar is what enables a bunch of mug first time bricklayers acheive the results that they do.
I now enough about bricklaying to know my bricklaying skills basically suck but I've built a good solid working oven with the forgiving nature of this stuff. If I built again I would use fireclay in the mortar mix or at least a clay rich brickies loam.

Regards dave
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Old 01-24-2013, 10:59 AM
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Default Re: Clay Mortar

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Originally Posted by cobblerdave View Post
Gudday
Disagree mick .like you said the refractory properties are really not required.
What you do get is a great mortar that's plastic,sticks to what is a really smooth surface easily, can handle lager gaps in the brickwork.I think the home brew mortar is what enables a bunch of mug first time bricklayers acheive the results that they do.
I now enough about bricklaying to know my bricklaying skills basically suck but I've built a good solid working oven with the forgiving nature of this stuff. If I built again I would use fireclay in the mortar mix or at least a clay rich brickies loam.
Regards dave
What was your mortar mix Dave?
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Old 01-24-2013, 11:24 AM
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Default Re: Clay Mortar

"If you use fired clay, say saved from cutting the bricks, then that is an inert filler"

That is not true, the brick powder has hydraulic properties, and is used in lime plasters to give a quicker set than the lime alone.
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Old 01-24-2013, 01:29 PM
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Default Re: Clay Mortar

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Originally Posted by dimitrisbizakis View Post
What was your mortar mix Dave?
1 part Portland cement
3 part sand
1 part lime
1 part fireclay
As per for forno recipe

I have also used a mix using no fireclay but brickies loam ( brickies sand with a clay content ) on an unrelated job and this mix had the same sort plastic character. You can move the brick a bit sqish it down and move it sideways without the brick losing its grip to the mortar.

Regards dave
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