Refractory Mix Cracking

[Westozchoppers]

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]

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]

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]

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]

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]

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]

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.

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]

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]

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]

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.

[bimbo]

Re: Refractory Mix Cracking

my old man told me that he saw fireclay for sale in bunnings the otherday so maybe check out there or ask them and they can get it in

[Adrian]

Re: Refractory Mix Cracking

my old man told me that he saw fireclay for sale in bunnings the otherday so maybe check out there or ask them and they can get it in

Which store? I've asked at Inglewood, Morley and Balcatta for ref. cement, fire clay and rock wool. Got blank stares or confused information at all three stores, and couldn't get any of these.

[Westozchoppers]

Re: Refractory Mix Cracking

Hi, I found the refactory cement I used of the shelf, would crack here in W.A.
I tried mixing it wet and dry and soaking the bricks, the so called air dryed mix I wouil stay away from and suggest using Forno Bravos recipe,fire clay,white sand and lime.

Pat

[sandgroper]

Re: Refractory Mix Cracking

Thanks for the info

It sounds like if white washed sand works so would plasterers sand

Brickies sand must have too much loam

Hi, I found the refactory cement I used of the shelf, would crack here in W.A.
I tried mixing it wet and dry and soaking the bricks, the so called air dryed mix I wouil stay away from and suggest using Forno Bravos recipe,fire clay,white sand and lime.

Pat

[sandgroper]

Re: Refractory Mix Cracking

Ask around for fire blanket, this is often rockwool

Which store? I've asked at Inglewood, Morley and Balcatta for ref. cement, fire clay and rock wool. Got blank stares or confused information at all three stores, and couldn't get any of these.