Who has used the calcium aluminate option for mortar?

[Lburou]

Update

Thanks for your thoughts.

We put down four inches of rigid insulation, the oven floor, the soldier course of half bricks and two chains of half bricks today.

The home brew with the calcium aluminate option worked just like the advice given in this thread and the other thread where I asked similar questions (Thanks to you knowledgeable people....you know who you are).

We used the home brew mortar with the calcium aluminate option. The mortar set up in about 20 minutes using half the volume of lime in the recipe (55-75 F degrees outside today). We discontinued the lime after the first batch (this is where you all say, 'We told you so!'.

While we filled the spaces between the bricks, the lime went back in. The option to use the accelerated set was welcome. We mixed less than a liter at a time. The fast set will be welcome as the chains get higher.

Thanks again for the information, it was very helpful.

[RTflorida]

Re: Who has used the calcium aluminate option for mortar?

I don't know that there is alot to be gained, after all, this is merely the mortar that is holding/setting your bricks in place. Only a small portion of the overall mass will be mortar, even if you follow the basic plan of using 1/2 bricks and not any sort of cut to fit. The basic 'homebrew' (portland/fireclay) has been proven to work perfectly for those on a budget. Refrax or Heatstop 50 for those who can afford it and want a true refractory.
Personally, I had zero experience with refractories (but plenty of masonry experience) going into my build so I chose Heatstop 50. Having always had pretty good luck with premix products it just made sense, why experiment with something that 1) I had no previous knowledge, 2) I only plan on doing one time. To me the $165 spent on 3 bags of Heatstop was a good/smart decision. As with everything, opinions and mileage will vary.

RT

[Lburou]

Re: Who has used the calcium aluminate option for mortar?

Portland is not refractory that is the whole point about using lime or calcium aluminate instead.

I was referring to the two recipes at the top of this post. The difference between the two is one ingredient: Either Portland or the aluminate. I was saying that if I have trouble using the aluminate mixture as a mortar, I can always fall back on the recipe with Portland. I'll edit the first post to make sure it says mortar in there

If I'm to believe the underlined portion of James' quotation at the top of this thread, then there is a lot to be gained by way of increased heat absorbsion and heat holding, as well as a faster heat up cycle. That is why I'm reconsidering this choice. I'll be using the mortar by the end of the week, I hope.

[david s]

Re: Who has used the calcium aluminate option for mortar?

Portland is not refractory that is the whole point about using lime or calcium aluminate instead.

[david s]

Re: Who has used the calcium aluminate option for mortar?

Lburou,
Just to get clear on what you are trying to do. Is it calcium aluminate mortar to use between bricks, or are you trying to make a castable refractory?
Dave

[Lburou]

Re: Who has used the calcium aluminate option for mortar?

The recipe for calcium aluminate mortar as given in the Pompeii plans calls for both lime and calcium aluminate cement. I don't know if anyone has tried this recipe but if they do then they will find that the recipe will create a mortar with extremely short pot life. It will go off in about 10 mins. Lime acts with calcium aluminate cement as an accelerant and in my experience the two ingredients should not be mixed because of this problem.

Thanks for the heads up on that David

I read all the threads on FB.com containing the word 'aluminate'. Several builders noted an accelerated set up time. Some eliminated or reduced the lime. Some doubled the calcium aluminate.

All mixed only a quart at a time so they never ran out of working time. Some even used ice water to mix because they reported the set up was accelerated in the heat. One thread suggested James remove the lime from the recipe.

Those are all issues I am willing to tackle, principly by reducing the lime, and if need be, switching to Portland

I'm open minded at this point.

[david s]

Re: Who has used the calcium aluminate option for mortar?

I use castable refractory a lot, but it is a premixed product and contains all the aggegate, flyash and other goodies. Pure calcium aluminate cement is very difficult to buy in Australia, I think the manufacturers prefer to sell the premixed product. We live in the tropics and I often have to add chilled water and keep the material and my barrow out of the sun, during summer, when mixing a batch.

[david s]

Re: Who has used the calcium aluminate option for mortar?

The recipe for calcium aluminate mortar as given in the Pompeii plans calls for both lime and calcium aluminate cement. I don't know if anyone has tried this recipe but if they do then they will find that the recipe will create a mortar with extremely short pot life. It will go off in about 10 mins. Lime acts with calcium aluminate cement as an accelerant and in my experience the two ingredients should not be mixed because of this problem.

[Lburou]

Who has used the calcium aluminate mortar (instead of the fireclay mortar)?
If yes, what was your set up time during construction?
Was the mortar very tempermental in high temp situations?

From the pompeii oven plans V2.0
Here is the recipe for fire clay mortar, where you measure by volume (use a bucket or shovel to measure):

1 part portland
3 parts sand
1 part lime
1 part fire clay

In between Refrax and fire clay/Portland cement mortar, you can make your own aluminate mortar. It is hard to work with, as calcium aluminate can be challenging. If you get the mix, or water wrong, it won't set correctly. It partially sets very quickly, and you cannot re-hydrate it, so you have to mix it and use it in small batches. Still, if you are trying to save money and want/need the heat resilience, heat conductivity and longevity of a true aluminate mortar, it works.

1 part calcium aluminate
3 parts sand
1 part lime
1 part fire clay

-James
__________________

From FB.com
The composition and density of an oven's thermal material is also important. Alumina and silica are two materials that have both high heat conductivity and high heat holding capability, and when used with a calcium aluminate binder (not Portland cement), they provide excellent cooking and longevity characteristics. An oven rich in these materials will heat up more quickly, hold heat longer and last much longer than an oven made from natural clay.