#1  
Old 03-31-2010, 01:59 PM
Peasant
 
Join Date: Jan 2010
Location: Cheshire UK
Posts: 36
Default who has used portland cement in the dome?

Hello

I'm stuggling to source HAC cement and fireclay, yep, I'm in the UK

I was wondering, who has used normal Portland cement and sand to build their dome and if you have, how has it held up?

TIA ... Mick
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  #2  
Old 03-31-2010, 02:41 PM
Raffy's Avatar
Apprentice
 
Join Date: Sep 2008
Location: Philippines
Posts: 213
Default Re: who has used portland cement in the dome?

I don't think cement and sand would hold up well. From what I know ordinary cement doesnt have the expansion capabilities when it comes to high heat. Since the refractories (firebricks etc) expand and contract during the heating-cooling cycle, the cement mortar has a tendency to crack.

Lime-cement mortars, on the other hand, tend to do better but I hope the experts can chime in on the characteristics of of this type of mortar.

If you haven't done it yet, look in the phonebook under the listing of "Refractories" for HAC Cement and fireclay. That's how I found my suppliers.

Good Luck!
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  #3  
Old 03-31-2010, 02:59 PM
eprante's Avatar
Journeyman
 
Join Date: May 2009
Location: El Cajon CA
Posts: 282
Default Re: who has used portland cement in the dome?

Frances used a mixture of just fireclay and sand, but that doesn't help you since it is the fireclay you are having trouble sourcing. The problem with using regular mortar is that the portland cement breaks down at high temps. The fireclay is in there to hold it together after the portland breaks down. Try pottery suppliers for fire clay if brick suppliers dont have it. Some suppliers also refer to it as mortar clay.

Good luck,

Eric
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  #4  
Old 03-31-2010, 04:24 PM
Banned
 
Join Date: Feb 2010
Location: Bend, Oregon
Posts: 131
Default Re: who has used portland cement in the dome?

Old school Oven builders use the old school mix
1 Part Portland cement
1 part fireclay
1 part lime
3 parts silica sand

You have to have Fire clay where you live (Cheshire UK)...Go to the phone book and call a mason that builds fireplaces and ask them what they use?
or

I bought my fireclay from Midland Refractories, West Bromwich, B70 944, Tel 0121 5253344. A 25kg bag is about 7.00.
or

YRPL Homepage


All you got to do is look
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  #5  
Old 03-31-2010, 04:40 PM
Neil2's Avatar
Il Pizzaiolo
 
Join Date: Oct 2006
Location: Vancouver Island
Posts: 1,374
Default Re: who has used portland cement in the dome?

Portland cement based concrete gives up the ghost at about 550 F. The internal bonds holding the particles together start breaking. Interestingly, this occurs not as the temperature rises past 550 but as the temperature falls back down from over 550 F.
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  #6  
Old 03-31-2010, 05:13 PM
Banned
 
Join Date: Feb 2010
Location: Bend, Oregon
Posts: 131
Default Re: who has used portland cement in the dome?

read this forum

http://www.fornobravo.com/forum/f6/h...rimer-914.html (High Heat Mortar Primer)

I like what this guy said

Quote:
Originally Posted by bimbo View Post
I'm sure if there was an issue there would be far more upset people on forums like this. You will get the odd crack or 2 but even if alot of the mortar failed what karl said is right it is really the brick pushing on the bricks either side of it wedging it in place
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