House Brick Horror

[Hysteric]

That's a very interesting chart.

Seems the big jump from 4/1 to 3/1 is the sand component

What are your thoughts about the refractory cement recipes from the link for the dome?

[david s]

It is only the very top (2 mm or so) of the vermicrete layer, in direct contact with the floor bricks that would be susceptible to temperatures high enough to degrade the portland. Because of all the air in the mix the temperature drop off as it gets deeper is sufficient for the Portland to survive IMO. Judging from pulling the spy hole plugs from kilns it is the tip of insulating refractory that may be bright orange hot (approx 1200 C) while the base of the plug, around 100 mm long, can be held in the hand (just).

There is an error in the table for the 5:1 vermicrete compressive strength. It should be 175-225. You are correct in assuming the sand has a big part to play in increasing strength. As a rule of thumb if you double the strength you'll halve the insulation value. The 5;1 ratio has proven adequate for both strength and insulation value for under the oven. For over the top, because it is not supporting weight, a much leaner brew can be used. I use 10;1 but anything leaner i find too hard to apply and it still needs to be firm enough to render against. If you are not concerned about it being insulate you can make it richer.

Calcium aluminate cement (CAC or refractory cement) in conjunction with perlite will produce an insulative mix. IMO a dense, rather than insulative mix is required for the dome so it has adequate strength as well as thermal mass, a requirement to store heat. You could use it for the under floor insulation mix, but i think you would be wasting your money as the portland /perlite or vermiculite mix has proved to be a good solution for many oven builders.

[Hysteric]

Thought I'd lay out the brick work for the floor:

Which presented the next problem. The thickness of the dome Insulation will dictate where the floor starts so as not to fall off the back of the stand.

Can Vermicrete be used as an insulating layer without the FB and if so how thick does it have to be?

[UtahBeehiver]

David S mentioned in his previous post the up to 10-1 can be used on the dome. IHMO 3-4 inches is an adequate amount without a CF blanket. Although CF blanket is more efficient it is not mandatory.

[Hysteric]

David S mentioned in his previous post the up to 10-1 can be used on the dome. IHMO 3-4 inches is an adequate amount without a CF blanket. Although CF blanket is more efficient it is not mandatory.

Thanks Beeehiver.

After looking at it i would imagine that the amount used for the vermicrete insulating layer below the floor would be also needed to insulate the dome. Considering that there was $150 in vermiculite and about 50$ in cement it doesn't really make sense to go that route when the FB will cost around $240. Not to mention that work involved and clean up.

I noticed in another thread some where David mentioned Rock Wool instead of FB. Might be worth a look .

[UtahBeehiver]

The CF board is a better insulator vs p/vcrete per inch thickness. I only mention p/vcrete since your original post indicated you were on a budget. Vermiculite must be very costly in your area to be similar in cost to CF board. I don't believe David S is an advocate of rockwool since it will absorb water more easily.

[Hysteric]

Everything is expensive in Australia!

The Vermiculite costs about $30 for a 100 litre bag.

Is the FB just for its insulating porposes?

What about alternatives like this:

It has a Thermal Conductivity of (ASTM C 518-10) 0.0345 W/m.K

[UtahBeehiver]

This link only goes to the general site and not a specific product. There are two other components necessary for a suitable floor insulation, one is temperature rating (should be at least a 1000 F) and compressibility rating at cooking temps, ie 90-100 PSI at 500 F. the of course K rating.

[Hysteric]

For the Dome

Try this:

JH_HardieFire_datasheet.pdf

[UtahBeehiver]

I am unfamiliar with this product, if for the dome, then the compressiblity factor is a non issue. Having no knowledge of the product I can't say yeah or nay

[Hysteric]

Ok guys its been a while as "Life is what happens while you're busy making other plans" I'm hoping to get stuck back into the oven over the christmas break. I have decided to go with the home brew method so want to clear up some issues. What would be the best sand to use? Link down at the bottom for sand types.



I need to use it for both the dome as well as the mold.

Also is Portland cement just a generic name for cement in general?

[Hysteric]

Time to pull my finger out and update this build.

I have been slowly chipping away at this build when time permits and that is mainly on long weekends as i have to do this on my own. Here are some pics but unfortunately i lost the in between pics when my phone broke.

It was done mainly over 3 stages with the front arch cast and then put into place followed by the walls formed up and cast in position following that.

The pictures now are of the build with the dome sand mold and paper strips ready for the dome to be cast to be started.






I have used stainless steel tie wire as a re-enforcing through out the build and all the pieces are tied together and it saved the arch when it cracked after moving it from where it was cast to its position.

https://www.bunnings.com.au/whites-1...-wire_p3040626

[Hysteric]

More pics:

The dome is around 60mm thick.

[Hysteric]

Sand cast removed:

[Hysteric]

Inside the oven. You can see some of the re-inforcing coming through the casting that needs to be trimmed off at the arch.