Refractory cement mix

[Donhoncho]

Hey I plan on building my first oven next week. I need some help I'm not quite understand what I need to add to refractory cement to make it strong. I have made the decision to use refractory cement because I plan on using the oven at above 900° of possible. The mix I found was 2 parts perlite 1 part sand 1 part refractory cement. My question is will that work https://youtu.be/hBvPs7CBf5Q in this video he makes that same mix the only difference is that it's Portland cement. This first layer of the dome I want to focus on strength I will make it 2-3in thick followed by a 4:1 perlite refractory cement mix that will be around 4 inches thick followed by a 2 inch ceramic blanket then a smooth finish I am thinking this will be enough to be able to get the inside of the dome super hot. The base I was planning on doing a 4 to1 perlite mix 6 inches thick and the oven floor would be standard fire bricks was also thinking of placing large pizza stones on the side the pizzas will go on and not in the side that the fires on. My biggest concern is with the refractory cement mix I have never worked with cement but I am going to give it my all would really appreciate anyones tips on refractory cement thank you in advance. Also if you could let me know if the floor would be thick enough to work as insulatinsulation.

[Kvanbael]

Hi Donhoncho,

Both the floor and the dome need at least 2 layers. The inner layer gets really hot and should be able store a lot of heat (like a battery). The next layer(s) are for insulation. Materials for inner layer should have good heat capacity and resist to high temperatures and contact with flames. Perlite makes no sense here. Adding perlite to a concrete mixture makes it lighter and a better insulator. That is the opposite of what you want for your inner layer. If you don't want to use firebricks for your dome, then have a look at other cast ovens on this forum (many use a mixture that is referred to as home-brew)

For subsequent layers, you suggest first a perlite mixture and next a ceramic blanket. Ceramic blanket is a great insulator and can stand high temperatures. So it makes more sense to use the blanket as your 'first line of defence'. Next you can further insulate with a perlite concrete mixture. Thanks to the blanket, the temperature will be more modest here, and you can work with regular portland.

I would suggest that you start from proven plans on this forum: You should find instructions for either a brick-based dome, or a casted dome.

[Donhoncho]

Thank you I am really new to cement mixing and wasn't sure if you needed to add anything to it to make it strong. But I guess it comes strong so I'll do first layer refractory cement followed by ceramic then a perlite cement mix then smooth it out. As for the thickness how thick should the refractory later be? 3-4? Inches? My total wall with was going to be around 8-10 inches 2inches being ceramic. Thank you for your response.

[Gulf]

As Kvanbael advises, I also advise you to do some research on the forum for cast ovens. There are many cast builds on this site for which david s has consulted. All your questions could be answered by looking at a couple of them.

Hey I plan on building my first oven next week. I need some help.....

You may be jumping in to quick before you really understand all that you need to know! Do yourself a favor and do some searching on this site. Also, stay off youtube

[NCMan]

As Kvanbael advises, I also advise you to do some research on the forum for cast ovens. There are many cast builds on this site for which david s has consulted. All your questions could be answered by looking at a couple of them.

You may be jumping in to quick before you really understand all that you need to know! Do yourself a favor and do some searching on this site. Also, stay off youtube

I 1000% agree about youtube!!

[Pizzarotic]

The mix I found was 2 parts perlite 1 part sand 1 part refractory cement. My question is will that work

If you goal is a lightweight oven then that mix should work fine.

I have made the decision to use refractory cement because I plan on using the oven at above 900° of possible.

You will probably get to that temp with a very active fire but the oven will have poor residual heat performance if that is important to you. (Perlite acts as an insulator)

My biggest concern is with the refractory cement mix I have never worked with cement but I am going to give it my all would really appreciate anyones tips on refractory cement

I would suggest a better mix would be 3 sand, 1 clay, 1 refactory cement. Mix in smaller amounts maybe a couple of buckets at a time as is can set very quickly.

I will make it 2-3in thick followed by a 4:1 perlite refractory cement mix that will be around 4 inches thick followed by a 2 inch ceramic blanket then a smooth finish I am thinking this will be enough to be able to get the inside of the dome super hot. The base I was planning on doing a 4 to1 perlite mix 6 inches thick

2 to 3" will be fine for the dome. As already advised, add the ceramic blanket over the dome, 3" to 4" would be appropriate, then add the perlite mix (as lean as possible 7:1 or 8:1) Portland cement is fine here.

Also if you could let me know if the floor would be thick enough to work as insulation.

Perlite base is fine but you will also need 2" ceramic fibre board on top of the perlite as your going for very high temps. Good luck with your build.