High Heat Mortar Mix question

[Frenchcanuck]

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]

Here's the high heat mortar primer, which gives two recipes:

http://www.fornobravo.com/pompeii_ov...at_mortar.html

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]

Thats an interesting fire clay mix I have never used lime..
1-2-6 is what I use.

1-Clay
2-cement
6-sand

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

[Dutchoven]

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]

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

http://www.calucem.com/

Hope this helps

Rgds

Balty

[Dutchoven]

Definitely if you can get calcium aluminate it will be better...it 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.
Best
Dutch