High Heat Mortar Mix question

[windage]

Re: High Heat Mortar Mix question

Finally, success! After a long discussion with the US rep for the REFCON MG by Calcem, I was pointed in the right direction, 2 issues were giving me fits; lack of stickiness and short "pot time, or work time".
1) lime is the enemy of Calcium Aluminate based cements, the residue in my work tools was enough to set it off in 3 to 5 minutes, and the Forno Bravo formula posted as adding one part lime is REALLY off base. Bought a new tub, trowel and fresh blending buckets..now "work time" is as long as I need. No more lime contamination.
2) stickiness was a function of adding more sand for more "surface area" to hold the water. I also tried his tip of adding a few drops of dish soap to entrain air...not sure if that helped or not...so the mixture I am using to lay (soaked) brick; 6 sand, 2 cement, 1 clay. I may even drop cement to 1 part when I parge the outside of the dome.

thanks guys

[fxpose]

Re: High Heat Mortar Mix question

Please correct me if I'm wrong, but my understanding of homebrew formula is based on using lime with portland cement, and no other type of cement.

George

[dmun]

Re: High Heat Mortar Mix question

Please correct me if I'm wrong, but my understanding of homebrew formula is based on using lime with portland cement, and no other type of cement.

You're right. Portland only.

That blend does work with portland, but not with alum sil, the lime is a no-no and sets it off in just a few (2-3) minutes..

This was discussed in the High heat mortar primer thread:

A quote from the thread by David S.:

When using calcium aluminate cement I found that adding lime in the mix made the mixture "go off" really quickly. On researching this I found, from the manufacturers (can't remember which one) that they said "do not add lime as it acts as an accellerant, which is exactly what I had found. Do not add lime if you want to keep it workable for a reasonable period (eg 1/2 - 3/4 hr or so) .The calcium aluminate cement is very temp dependant. Use chilled water if using on a hot day and don't leave the stuff in the sun to get hot.

There's much less practical experience with using the calcium aluminate mortar here. It has the reputation of being difficult.

[windage]

Re: High Heat Mortar Mix question

as dmun pointed out; "There's much less practical experience with using the calcium aluminate mortar here. It has the reputation of being difficult."

My initial search on this forum for "calcium aluminate" mortar turns up the Forno Bravo tuturial which instructs one to add lime in the recipe...it was only when that turned out so bad, did I do further searching and discovered the lime no-no issue. Further, I want to add that simply using old tools or mixing pans that have portland based residue on them also triggers the same "hot to trot" set up time.

I just share this info as there is very little about that product here. I also want to add my experience as being more favorable than previous posts would indicate.

[windage]

Re: High Heat Mortar Mix question

I have been converted! Happy day! The cal alum recipe is working great. I had to go buy one of those small (4cuft) Kobalt mixers at Lowes today, $300 to mix the components dry, but made things much faster.
3 benefits I discovered;1) no lime issues with hands or leaching later, 2) no "small joint" mandate. The cal alum cement is a stand alone (and castable) refractory, in other words, at 2624f (Calucem's refcon mg) it can take the heat without degrading (made the bricks around the arch / transition go faster) so gaps full of mortar may not look as professional, but they're fine. And 3), not only is it water resistant, (like portland), it's stronger/faster.

So, guys, take another look at the cal alum (CA) cements for your project. It may not deserve the knocks it has recieved.

And will someone tell FornoBrave to please change / update their page about CA high temp mortars....it cost me several weeks, I was not in a "gosple mood" and was "fixin't slap granny" over it.

More pics posted over at the "commercial-81 inch" thread.

And as always, thanks for the encouragement.

[david s]

Re: High Heat Mortar Mix question

Windage,
You've got me doing it now.
"The lime also acts as an accelerant with calcium silicate cement." In my previous post.
Of course I meant Calcium Aluminate.

[david s]

Re: High Heat Mortar Mix question

Windage,
You are quite correct. The FB recipe does include lime and CA cement. This is wrong and should be changed. Obviously the recipe had not been tried, or the author had no knowledge of the incompatibility of the materials. I only found out through discovery when I tried adjusting my recipe and adding lime. On researching the product info it also says the two should be avoided. James can you amend the recipe?
Dave

[windage]

Re: High Heat Mortar Mix question

I invented that group of chemical-sounding-words to make myself seem important and mysterious. The fact that others too, such as yourself, are using this catchy term, indicates that there may be a market for yet another, even more difficult to use mortar.
I will begin work on developing "aluminum-silicate" cement immediately!

Staying up into the wee hours reading data sheets and techinical specs about CA cement and the bonding/melting of silica sand is probably how I came up with that..and now I've polluted your mind with yet another useless piece of garbage...apologies.
Rog

[david s]

Re: High Heat Mortar Mix question

Windage, That's an excellent post. Keep them up. Now I understand why you call yourself Windage.
Dave

[windage]

Re: High Heat Mortar Mix question

Windage,
You've got me doing it now.
"The lime also acts as an accelerant with calcium silicate cement." In my previous post.
Of course I meant Calcium Aluminate.

AHA ! I re-discovered the place I had read about alumina-silicate, (just one of the many ways I have corrupted the name Calcium Aluminate cement);


http://www.heatstoprefractorymortar....AT-STOP-50.pdf

Roger