Castable oven - need help!!!

[rrfsgh]

Hello,

I have been trying to source a castable refractory in Michigan because the high cost of shipping. Our local refractory store carries a product call Sparcast 30L which they say can be used to cast an oven. The product is relatively inexpensive, and even more so since there is no shipping. Product specs are attached. I believe the density may be close to that of firebrick.

I would use this for the dome, and use large firebrick tiles for the floor. The oven would ONLY be used for pizza.

I would really appreciate some comments regarding this idea so I can determine if these materials can produce a quality oven. I'm planning on putting it on a trailer. I made a brick Pompeii oven for my home which we love. However, I think a castable oven would be better for trailer use due to durability.

Thank you!
Rob

[mbclark123]

Forno Bravo kits include the dome, floor, insulation, door, chimney and free shipping

[rrfsgh]

Thanks but I'm looking to cast my own oven. I've seen several castable oven projects from other builders on this forum. The kit route is definitely the best option for the average person, especially considering free shipping on a complete kit (is that new!!)

I am a pretty hard core do it yourself person, and want to tackle this build in stages over time rather than one big purchase. I wanted to purchase a cast mix (refmix?) from Forno Bravo but it was not available anymore. They suggested I post my question to the building community here. Thanks to anyone who has input.

[UtahBeehiver]

Get with David s from Australia here is one of the forum's expert on on castable refractory

[Gulf]

Just to second Russell on David S, Here is "quick search" of the forum for David S and his recomedations for castables. He has advised many on this subject. The Material Safety Data Sheet (MSDS) on any product holds much useful information. Here is the link. Click on the MSDS for 30L. It will open up as a word document.

I hope this helps .

[jpar]

Where in Michigan? Nothing wrong with the Spar castable. We've cast hundreds out of a similar product. For use in a trailer, you can't take any short cuts. Castable water requirements must be followed exactly. Castable must be vibrated during installation, and be dried and cured carefully. ANY shortcuts will result in cracking. We have had luck with the attached product.

[rrfsgh]

Thanks Utahbeehiver, Gulf and jpar! I will try to reach out to Davis S and read his posts.

I also spoke to a refractory engineer and he highly recommended renting a towable horizontal shaft paddle mixer instead of a typical drum cement mixer. He said a drum mixer would ball up the product and most people would continue to add too much water which would ruin the mix. I understand getting the water amount is critical for strength, and the water range is specified on the product. He also said the forms should be covered with plastic until cured.

In case anyone reading is interested, I found this video showing the thixotropic property of castable refractory: https://www.youtube.com/watch?v=a91wgdVBR2s The product is thick under static conditions but will become thin and flow down into the mold when vibrated.

[david s]

Go to a refractory supplier and tell them what you are doing. There are many different castables, you need a dense castable not an insulating one. Most will have a rating which is around double your requirements so there's no need to get one that's rated for really high temperature. You really only need one that will cope with up to 600 C, most castables are rated to go to around 1300 C or over. Some builders have used the Homebrew as a castable, but I have no idea how it would stand up to use over time (6-7 years of use)
The easiest way to cast a dome is to do it in place over a sand mould and troweling the castable over it. Making moulds for a one off oven is not really worth the time involved.

[rrfsgh]

Thanks David!

I would like to use the sparcast 30 L since it is all I can find locally and appears to have the desired qualities (as far as I can tell). It's density is 138lb per cubic foot.

How do you recommend mixing the product? Should I rent a horizontal shaft paddle type mixer or is there a way to achieve a good mix by hand? I heard it has a tendency to ball up in drum type mixers.

[david s]

That density is what you want, although Sparcast 30 has a very high service temperature rating of 3000 F. You won't even get to half of that temperature. If you shop around you may be able to obtain a cheaper product with a lower temperature rating. I've found that if you add the required amount of water then the mix will be too dry to be workable. Others have reported the same. If working alone mix only half a 25 kg bag at a time in a barrow. If you have two operators mix a whole 25 kg bag at a time, adding just enough water to make up to a stiff mix. The reason small quantities should be mixed at a time is because the stuff goes off really fast. You don't want half a barrow gone off before you can place it, it's expensive stuff. Add stainless steel reinforcing needles to a min of 2% of the weight of the dry mix if you can get them.