Ceramic fibre board AND calcium silicate base

[creasy987]

Hi, I'm just getting the last few bits of material for a build starting this coming week.

I'm looking at the boards for below the brick cooking surface…

Here in France, materials are expensive and I was considering 25mm of ceramic fibre board (1430c) and then 25mm of calcium silicate (1100c) below the board.

My order would be - bottom to top…

100mm reinforced concrete base
25mm calcium silicate
25mm ceramic fibre board
Refractory bricks for cooking floor

Does this sound reasonable/enough?

Would a perlcrete layer be a benefit too, below the boards?

Cheers,

James

[UtahBeehiver]

What exactly is the ceramic fiber board? Specs would be nice. If there cost differential between CaSi and fiber board? 50mm in the minimum "high tech" insulation thickness. A 25 mm 5 to 1 pcrete layer would improve the oven to sustain multiday cooking and relatively inexpensive. Do install some weep holes in the concrete base for water egress.

[creasy987]

Hi UtahBeehiver,

Thanks for the reply.

This is the spec on the website for the ceramic fibre board.

Vacuum molded ring.
Classification temperature: 1430 ° C
Maximum operating temperature: 1350 ° C
Density: 300 Kg / m3
Low thermal conductivity.
Good mechanical resistance.
Good resistance to thermal shock.
Good resistance to penetration of liquid metals.
Good resistance to gas erosion
Cold crush resistance (MPa): 0.1 - 0.3
Easily machinable.
Thermal conductivity :
200 ° C 0.08 W / MK
400 ° C 0.11 W / MK
500 ° C 0.13 W / MK
600 ° C 0.15 W / MK

It's €75 for a 25mm 1000x1200mm sheet.

The CaSi is €13 for a 25mm 1000x 610mm sheet.

So CaSi is 2/3 cheaper than ceramic fibre board - is there much of a difference between the two?

How many weep holes would you recommend for a 42 inch oven? This would go through the pcrete layer and the concrete slab?

Cheers,

James

[UtahBeehiver]

If the CaSi is the go to high tech insulation. If it has these characteristics then I would go with "min" 50 mm of CaSi and skip the fiber board especially since it less costly.

Thermal Conductivity - 0.07ish at 260C
Compressibility - 600ish kPa

Weep holes in concrete hearth only 2-4 3/8" to 1/2"dia. weep holes are enough

[creasy987]

Ok great, I've emailed the supplier to request a spec - so will see.

I'll probably go with 100mm of CaSi then, as it's not daft expensive and do away with the pcrete layer.

Or would you recommend pcrete underneath that too?

Cheers!

[creasy987]

Hi Russell,

Would you say the below is suitable for the CaSi?

They do it in 25, 50, 75 and 100mm sheets - what do you think would be best? Would the pcrete layer be advisable regardless of the CaSi thickness?

Temperature of use	16 Kg/cm2
Density Kg/m3	260
Porosity % (%)	90 %
Compressive strength	16 Kg/cm2
Modulus of rupture	12 Kg/cm'
Shrinkage at 1000°C	1,00 %
Thermal conductivity inW.(mh)at
200°C	0.07
400°C	0.09
600°C	0.1

Thanks in advance!

[UtahBeehiver]

100 mm of this CaSi is more than adequate so Pcrete is not necessary, but keeping water away from CaSi is. You can search the Forum for various solutions, weep holes and placing CaSi on scrap ceramic tiles are a some. The the Compressive strength by my calcs is 227 psi, more than enough, the the K values are in range for CaSI.

[david s]

You might also like to look for a waterproof cal sil board.