between vermiculite base and oven floor?

[slowfood]

I laid the vermiculite base today, 3" of Vermiculite concrete sitting on 2" strong concrete. I had trouble getting the Vermiculite at a good level finish, What is best to put between the vermiculite concrete and the oven floor to keep everything level and strong? Thank you

[scottme]

Assuming your oven floor will be firebricks, I'd put a thin layer of 50-50 sand and fireclay on top of the vemiculite and lay the floor on that. Mix some water into it to make it easier to adjust the individual bricks and get your floor nice and level.

[slowfood]

Thank's. What excactly is fireclay? I have almost 40kgs of refractory concrete cast mix I was thinking of sieving out the larger aggregate and using that, Do you think it would work? My floor is made of several pieces I cast myself... The oven is mobile by the way but hopefully shall be tied together pretty well. Thank's

[tonyb]

I think fireclay covers a range of ground up ceramic material eg firebrick. Its not cementatious like refractory concrete mix, ie it doesn't set into a solid mass when mixed with water, it just forms a slurry/mud.

I think you can pretty much use any material for bedding the base, some prefer dry materials eg sand, and others prefer wet. The disadvantage of using refractory concrete in a firebrick structure is that it will act like adhesive and make replacement of an individual brick, if ever that's necessary more difficult. I'm not sure it makes much difference in a precast design. The most important thing is the ability to create a smooth/level surface, so if you do decide to use the concrete mix, I would be inclined to sieve out and use the finer rather than the coarse material depending how small/big the larger aggregate is.

[cannyfradock]

Slowfood

I bought a couple of 25kg bags of refractory concrete from Kilnlinings...on my last build. I didn't really need it, I just wanted to see the composite of the stuff. It was very fine grit and powder. If your ref. con. is the same consistency I would use it without sifting. Just make up some semi-dry (by hand....not with a machine) so you end up with a damp mixture and lay your refractory floor segments on about 30/40mm of the mix. You should have enough play in the mix to lightly tap your pieces into place with a heavy rubber mallet.

Rado Hand has a good explanation on the make up of powdered fire-clay... www.traditionaloven.com/articles/101/what-is-fire-clay-and-where-to-get-it

Terry

[turkey]

powdered ball clay would be just as good, or regular clay watered down to a slip then mixed with sand.

I suspect super weak concrete or probably better lime mix would work as you want enough to hold the bricks but not enough to affix them firmly. 10:1 or more so it was very very weak? Just a random idea tho.... I used fireclay and sand 1:1