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Frenchcanuck 07-14-2007 06:12 AM

High Heat Mortar Mix question
Hello, I have conflicting formulas (by different dealers/people etc..)
One mix is this:
1 part cement, 1 part fireclay
another is:
1 part cement, 1 part fireclay, 10-12 parts sand

Seems like an awful big difference in mixes, or is it just me???

dmun 07-14-2007 09:52 AM

Re: High Heat Mortar Mix question
Here's the high heat mortar primer, which gives two recipes:

My advice? If you have any leeway in your budget, spend it on a dry refractory mortar mix like Heat-stop, or the Ref-mix that FB sells. It's closely matched to the expansion of the firebricks, and doesn't use portland cement, which isn't fire resistant. As a bonus, it's easy to work with. Heat-stop mixes and spreads like peanut butter.

Unofornaio 07-14-2007 10:27 AM

Re: High Heat Mortar Mix question
Thats an interesting fire clay mix I have never used lime..
1-2-6 is what I use.


Where did the recipe on the primer page come from? Id be interested in the reasoning..sound like some seriously sticky stuff..:eek: which for this build is defiantly a good thing.

Dutchoven 07-14-2007 10:52 AM

Re: High Heat Mortar Mix question
From what I am told the hydrated lime adds stickiness to the mortar in its uncured state and that it sets a little softer and responds to expansion and contraction slightly different. I have also heard that hydrated lime fluxes at a different temperature than that of the portland so when the portland is gone the lime is still there.
The mixture I used for my oven 1/3/1/1, portland/sand/fireclay/lime and that was given me by the grandson of an oven/heater mason from Czechoslovakia.
Any way that is my 2 cents!;)

Balty Knowles 07-14-2007 08:10 PM

Re: High Heat Mortar Mix question
From what I've read you should avoid portland cement in the mortar mix but use calcium aluminate.

Calucem the manufacturers of Lumnite gave me the following mix.

2 sand
2 Calcium Aluminate
1 Fire Clay

I used this for the chimney because I ran out of Refmix. It is quite difficult to used except in very small batches. Seems to go off in about 15 minutes.

if you can justify the cost I would highly recommend Refmix

You can check out Calucem on the web, give them a call they're very helpful

Hope this helps



Dutchoven 07-15-2007 08:09 PM

Re: High Heat Mortar Mix question
Definitely if you can get calcium aluminate it will be is a bit harder to find however. It will also set sooner and harder than a portland mix and cannot be rehydrated so for a novice bricklayer it will be important to mix small batches so as not to waste it. It will be a bit more difficult to knock apart once the mortar has set a bit but, hopefully you won't have to be concerned with that.;)

windage 05-17-2010 01:01 PM

Re: High Heat Mortar Mix question
Tried a small batch of the 2-2-1 and much better, a little stickier...though still very firm, meaning that when the mortar hits the bricks, it really gets firm fast. I may need to wet them down harder....seems like I can't mash any extra out, making the leveling up difficult.

ThisOldGarageNJ 05-17-2010 03:14 PM

Re: High Heat Mortar Mix question
calcium aluminate on ebay.... Secar 71 Calcium Aluminate Cement Refractory - eBay (item 140352762915 end time Jun-13-10 06:52:31 PDT)

windage 05-17-2010 05:43 PM

Re: High Heat Mortar Mix question
$24 plus shipping for 10lbs!!...that comes out to $215 per bag and I have 7 bags of alum silc to sell if I can't get this recipe to work out...I may go to Lars formula and just use portland.

david s 05-18-2010 01:48 AM

Re: High Heat Mortar Mix question
I would not buy the stuff on Ebay because it has a short shelf life- about 6 months. You could get it and find that it's already gone off. Buy it from a reputable refractory supplier. It is expensive and tricky to work with- it goes off fast and is quite temperature dependent

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