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-   -   Refractory Mix Cracking (http://www.fornobravo.com/forum/f28/refractory-mix-cracking-3037.html)

Westozchoppers 12-08-2007 04:22 PM

Refractory Mix Cracking
 
Hi Can Anyone Tell Me Why ? The Refactory Sila Mix Im Using In Perth W.A
Is Cracking, Im Weting The Bricks And The Mix Im Making maybe A Little to moist

Cheers Pat

CSWolffe 12-09-2007 11:51 AM

Re: Refractory Mix Cracking
 
Did you use the premixed refractory mortar? Im building a small scale prototype(cant afford the real one yet, but want to practice with the materials), and here in Salt Lake the premixed product is much easier to get ahold of. It comes mixed VERY wet, and from my experience, wet cements are more likely to crack. More water in the mix means more volume, and when the mix dries(even though it is a chemical reaction, not just drying), water is forced out of the cement, and this means a loss of volume. this causes shrinking.
I think. Anyone more experienced here wana back me up?

Westozchoppers 12-09-2007 03:04 PM

Re: Refractory Mix Cracking
 
Cheers for your input!
I,m not using a premix with water, rather a dry - premix. But what I've since learned in the forums , The're suggesting not to use an air-dry, mortar, for exactly the reasons I'm encountering !

Cheers
Pat

Neil2 01-01-2008 03:38 PM

Re: Refractory Mix Cracking
 
All refractory mortars I know of will shrink somewhat. If you are spanning a joint of more than 1/4 inch or so expect cracks. If you want to span a larger joint - extend the mortar with a sharp sand (mortar sand or silica sand). For 1/2 inch span, go with a 1 to 1 ratio, 1 inch span try a 3 sand to 1 mortar mix ratio. If you have tapered joints, try having two mortars - "neat" for the tight part and "extended" for the wider part.

Westozchoppers 01-01-2008 09:55 PM

Re: Refractory Mix Cracking
 
Cheers for the info Neil, ended up going with the fireclay , lime,sand and cement mix recomended by Forno Bravo, and now have completed the oven. Now been sitting for two weeks and about to start firing. Will post photo's from start to finish in the next week.

Cheers
Pat

Nokka 01-04-2008 09:16 PM

Re: Refractory Mix Cracking
 
Hi Mark here from NSW Australia. I hope this is a suitable place to ask this question but...
I've gotten hold of some high temperature raku clay and intend to mix it with lime and sand for a dome mortar - what do you guys reckon??
ta

Adrian 01-11-2009 07:46 PM

Re: Refractory Mix Cracking
 
Quote:

Originally Posted by Westozchoppers (Post 21880)
Cheers for the info Neil, ended up going with the fireclay , lime,sand and cement mix recomended by Forno Bravo, and now have completed the oven. Now been sitting for two weeks and about to start firing. Will post photo's from start to finish in the next week.

Hi Pat;

Where did you find fire clay in Perth? And did it hold up OK once fired?
I'm in the process of finding materials at the moment, so an advice for stuff in Perth greatly appreciated.

Westozchoppers 01-12-2009 09:35 AM

Re: Refractory Mix Cracking
 
Hi Adrian,
There's a pottery shop in Occonor. I cant remember the name right now, should be in the yellow pages under pottery supplies. There's also a perlite manufactorer in Jandacot. Fireclay has held up well well no problems as yet!If You need further help contact me at pattydazzler@hotmail.com

Goodluck
Pat

nissanneill 01-12-2009 12:01 PM

Re: Refractory Mix Cracking
 
Hi all,
well here we have a thread with a few newbies from this wonderful land of ours. Great to see the Australian increasing the forum numbers.
Welcome to Westozchoppers (Pat), Nokka and Adrian.
The poor mans version for the mortar works fine and I haven't had any problems with mine over the 18 month build time.
Post some pics so we can all share your joys.

Cheers.

Neill

Adrian 01-12-2009 11:38 PM

Re: Refractory Mix Cracking
 
Thanks Pat for the pottery shop suggestions. I live North of the river, and found that Stilletano's Home Hardware in Malaga stock Fondue cement. It's $47 for a 20kg bag, but it would probably cost me that much in fuel to drive to Oconner!

They can also get rockwool insulation for about $50 / m2.

I've found the perlite place in the yellow pages and will give them a call to get a price.


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