Mortar choice issue - need help to decide

[dvonk]

Hi!
There are several options available on the reasonable price - common fireclays, professional refractory mortar (28% - Al2O3) and ready-to-use waterglass-based mortars.
It seems now that I'll use Hendo’s Dome Gauge (http://www.fornobravo.com/forum/f28/...idea-2573.html)
and will cut bricks on two sides, so, "horizontal" seams on the outer side will be relatively thick and the "vertical" seams should be really thin.

I've heard that waterglass is suitable for thin seams only and (sound strange for me) that is not good from the health point of view.
What to choose - water based refractory mortar or waterglass-based mortar?

Thanks in advance,
Dimitry.

PS. Have no masonry skills at all, but seems to be well educable (and self educable).

[dmun]

"Waterglass" is a new word to me in the mortar department. Do you have a link?

[dvonk]

It's a new word for me as well, I'm not sure that its a best way to translate the Russian term, but what I've got from the on-line dictionary:

liquid glass
soluble silicate; water glass; liquid silica glass
liquid silica
alkali silicate; soluble potassium; water-glass
soluble glass; soluble water glass; sodium silicate solution; sodium silicate

OK, here it comes: Sodium silicate - Wikipedia, the free encyclopedia

[dvonk]

I've tried to find, but failed - everything is in Russian. Generally speaking, that kind of mortars consists of chamotte, "hydrated" with sodium silicate, as I've understand it helps significantly reduce amount of water and as a result - reduce shrinking as it dries.

[david s]

Dvonk,
I think you're right, sodium silicate acts as a defocculant to make the materials more viscous. But you need to mix it well to make it work. Another term for it is thixotropic.

[dvonk]

On Russian fireplace and stove forums I've mentioned opinions that its not suitable for thick seams (only for 1-3 mm) - but all professional people here in Russia are so smart so they never agree with somebody else, so I'm in doubt

[dmun]

Hey, this sounds great:

Refractory use

Water glass is a useful binder of solids, such as vermiculite and perlite. When blended with the aforementioned lightweight aggregates, water glass can be used to make hard, high-temperature insulation boards used for refractories, passive fire protection and high temperature insulations, such as moulded pipe insulation applications. When mixed with finely divided mineral powders, such as vermiculite dust (which is common scrap from the exfoliation process), one can produce high temperature adhesives. The intumescence disappears in the presence of finely divided mineral dust, whereby the waterglass becomes a mere matrix. Waterglass is inexpensive and abundantly available, which makes its use popular in many refractory applications.

and this:

Concrete treated with a sodium silicate solution helps to significantly reduce porosity in most masonry products such as concrete, stucco, plasters. A chemical reaction occurs with the excess Ca(OH)2 in the concrete that permanently binds the silicates with the surface making them far more wearable and water repellent. It is generally advised to apply only after initial cure has taken place (7 days or so depending on conditions). These coatings are known as silicate mineral paint.

What is the stuff? Where do we get ahold of it?

On Russian fireplace and stove forums I've mentioned opinions that its not suitable for thick seams (only for 1-3 mm) - but all people here are so smart so they never agree with somebody else, so I'm in doubt

Yes there is a danger of the "not invented here" mentality on this forum, but I think we're open to new ideas when they are good ones. The Russians have long experience with wood burning, and I for one am interested in tapping into that knowledge.

As far as mortar thickness, the commercial refractory mortars are specified for thin joints, but people have used them for thick joint pompeii builds successfully.

[dvonk]

"all people here" means - here, in Russia ))
Every professional here has his own exceptional opinion, so never agree with each other. I have to edit me my comment - since here, on this forum, people looks like more consolidated.