Furnace Cement safe to use??

[LakeSapele]

Hello all! This is my first post of hopefully a bunch of conversation. I started building my pizza oven almost a month ago and I am at the point of making the actual oven part. I built the back wall and the cooking area utilizing furnace cement. Reading a little bit more I’m not sure if that is safe. Please let me know if you can if this is safe or if anybody else has done so in their’s. In particular Durst furnace cement. Thank you so much for any input I truly appreciate it! Please see below to a few pictures of where I have used it.

[UtahBeehiver]

You will have to look at the MSDS, the forum recently had a discussion on cured and uncured mortar repair but it was a split opinion.. On another note, looks like you are doing a barrel oven but from the pics I cannot tell how you are insulating under the floor and barrel walls. Is the floor a double layer of splits (1.25") fire brick?

[LakeSapele]

Thank you so much for getting back to me! I looked at the MSDS and couldn’t really decipher it. I did call the manufacturer and he said (Vinny) that it was safe once it has cured. I figure to be even safer, I will build a wall in the interior back and cook on 2 pizza stones each 12x15.

in answer to your next question, yes, the floor is a double layer of the 1.25” bricks... Hope this is ok. And the walls are the 1.25” then I was thinking of using 2-3 layers of ceramic fiber insulation draped over top of the barrel then red brick outside that in a cube non domed fashion.

Any thoughts I would love to hear them! And thank you for your time.

[UtahBeehiver]

1.25" barrel walls do not provide enough thermal mass for an oven and mortar joints are not stable enough being this thin. You did not answer the question about the floor insulation, floors sitting directly on a concrete will drain the heat away from the floor through the hearth.

[LakeSapele]

Crud. Ok, so start over is what you are saying or can this be fixed? What I’m hearing is there has to be some sort of separator or insulation between the floor and the concrete base. Any suggestions would be welcome and appreciated!

[Michael Thomas]

I've learned that you can use one or two of a few options: (1) 2" of ceramic fibre board, (2) 4" of insulating concrete (5:1 vermiculite/cement mix), or (3) insulating bricks. I am planning to go with #1 because its easier to install than #2. #3 is also easier but I think #1 is more effective. By effective I mean that it is a better insulator, which is measured in watts/m*K (pretty much joules transferred per second between two places - in this case your wood fire and concrete slab.

I've heard of people combining #1 and #2 or doubling up on #1. The vermiculite can be obtained from a chemical store or large garden centre. It should be mixed by hand with the cement.

[andits22]

Yes, it is safe. I have also tried this to fix my bamboo flooring and it gives me best result without any harm. Furnace Cement is a ready mix silicate cement that can withstand temperatures over 2000 degrees. Furnace cement is perfect for sealing between firebricks and sealing the collar of your wood stove.