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Chris 11-15-2006 12:43 PM

Refractory "cement" vs. Refractory "mortar"
I'll be pouring the hearth soon, and have located a source for firebrick and perlite.

A local masonry supply suggested refractory cement for the oven. It is sold in a 1 gallon container for $14.50. He didn't have much more information, other than that it has the consistency of pancake batter.

It sounds to me that this is not quite what I want for Pompeii dome construction. Can I mix this cement with sand to make refractory mortar?

Refrax is described as "refractory mortar" not "cement". I assume this does not have a batter-like consistency, and will fill the larger gaps in the outside of the dome.

The local shop also has fireclay, so I might just go the fireclay/portland/sand route. I expect this oven will be used 2 or 3 times per month.

I hope this is not a FAQ, since "cement" was not described in the
High Heat Mortar Primer.

p.s. I tried to price the shipping of Refrax from the fornobravo store, but kept getting webpage errors. How much Refrax would I need for a 42" Pompeii dome?


Austin, TX

james 11-19-2006 05:24 AM

It sounds like an air-set mortar formulate for indoor, thin joint fireplace installation. Some builders like it because it is water soluable for easy clean up on straight wall firepalces. But air-set mortars do not stand up to water, and should not be used outdoors. They are also for very thin joints, and wouldn't work on a brick oven.

Refrax, and the fireclay mortar that you can make have a similar feel to mason's mortar, and of course are heat resistant. They do give your dome some structural support and make the inward curve secure to build.

Why don't you send an email to Tammy ( if you would like us to get you shipping info on Refrax. Sorry the Store malfunctioned.

There is a good link on air-set refractory mortar/concrete here:


wlively 11-19-2006 11:31 AM

Heatstop also good

HeatStop 50 mortar is also a good mortar to use. Not as pretty (grey) as the refrax, especially with your bricks, but it is available locally to you.

James is very correct, you don't want the pre-wet buckets, but the dry mix.

Here is a link for you.

ACME Brick
631 Round Rock West Dr.
Round Rock, TX 78681
512 244 7600 (fax 512 244 9040)
Contact: Shawn McElroy, sales mgr, 512 293 8217; Tama Humes, purchasing

Chris 11-19-2006 12:18 PM

Thanks everyone!

I spoke to Tammy on the phone. The shipping will be too much for me, so I'm going to check out the heatstop 50 locally.

The masonry store near me sells 10 lb bags of fireclay for $4.50. I might as well get heatstop at that price! I did buy a few bags for bedding the hearth bricks.

Sunny, calm, and 70 degrees (21 C). Perfect weather for oven building. I'm going outside right now to lay down the perlcrete hearth.


Balty Knowles 04-26-2007 03:11 PM

Re: Refractory CEMENT vs. Refractory MORTAR
I'm a little confused as to the thickness of the mortar joint. The Refrax page says use minimum 10 mm thickness whereas most of the posts I've read have the bricks touching on the inside or a 1/8 joint. I like the look of the Artigiano construction looks like a 3/8 joint. I will taper the brick faces to be close to prallel. Am I OK with he wider motar joint using Refrax or Remix. By the way whats the difference?

Chris 04-28-2007 06:32 AM

Re: Refractory CEMENT vs. Refractory MORTAR
The brick faces touch on the inside, but only along one edge. Then, unless the bricks are tapered, the joint widens out towards the outside of the dome. Especially with the portland/fireclay mortars, some people try to minimize the area of mortar exposed to direct flame in hopes of reducing spalling, hence the very thin joints on the surface.

I think a quality refractory mortar like Refrax will be fine with a 3/8 joint. Carry on!

christo 04-28-2007 06:22 PM

Re: Refractory CEMENT vs. Refractory MORTAR
My limited experience (almost through a bag of it) with the Refrax mortar from Fornobravo is that once this stuff sets up it becomes really tough.

When cutting through some mortared up sections, I could tell the saw was bogging down when I hit the refrax mortar areas. The pieces I cut off did not separate from the brick. 10mm is close to 3/8 of an inch - I think you will be fine.


james 05-01-2007 04:29 AM

Re: Refractory CEMENT vs. Refractory MORTAR
My experience is similar to Chris'. I think RefMix is very tough stuff. It has a make-up that is very similar to the FB ovens by %, but it is more dense, and it has setting agents (though I can't do a good job of explaining what they are are or how they work). It sets very fast and it gets extremely hard. You can literally watch it work.

We changed the name to RefMix from Refrax because of a copyright issue in the states. It's the same stuff, and we will be calling it RefMix in the U.S. from now on.

I know I have said this before, but Refrax is the "kleenex" of refractory mortar in Italy. Most building supply stores carry it (there are 4,000 dealers for Refrax and the FB ovens in Italy), and you say "gimme three bags of Refrax" and they know what you want. In a country built out of brick, where there are a huge number of wood-burning fireplaces and ovens, it's a good thing having the top refractory mortar. (End of product plug).


Balty Knowles 05-01-2007 08:03 AM

Re: Refractory CEMENT vs. Refractory MORTAR
OK, OK I'm convinced.:rolleyes: I was going to try to make my own mortar but with an appreciative thanks to the forum I just decided it's not worth the risk, I'll use the calcium aluminate I bought for the outside casing & build the dome with Remix. I'll find a reason to drive up to your place this week or next to pick some up from Forno Bravo. In Windsor right??

My basic question though has been this:- What is the joint size?? Remix bag says 3/8 every one else says 1/8. I intend to use the 3/8 joint because I like the look, any problems with this??

How many bags should I pick up? Plans say 9 but my joint will be wider and parallel.



diy 09-12-2009 08:31 AM

Re: Refractory CEMENT vs. Refractory MORTAR
Vitcas ready mixed refractory cement / mortar is suitable for jointing, in all high temperature applications. Recommended bed for jointing fire bricks is 3mm.

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