Calcium silicate brick

[polker8]

Hello, I am new to this forum and I have a question about using sand lime bricks or calcium silicate bricks. The dome on the oven needs to take the heat of the fire but i dont have the funds for real fire bricks, I have been offered these bricks for free so was wondering if they would work, I have seen the home brew fire mortar contains lime to withstand the heat so was thinking maybe the bricks would work. Does any body know ?

[UtahBeehiver]

I suggest you purchased the FB eplans ($3) it is a good baseline (a little dated) and read the appendix that has a brick primer subject in it.

[polker8]

Hi, Thanks I do have the plans and have read the appendix on bricks but it does not mention sand lime bricks. I was thinking if lime is good for the mortar then maybe it is good for the bricks in the dome. I have storage heater bricks for the floor so i am sorted there.

[Gulf]

Calcium silicate brick are a refractory brick. However, they are not a dense refractory brick. They will not retain heat very well. They are also too soft imo for a WFO. They will ebrade easily from wood loading, by being bumped whith an oven peel ,or by pots and pans. Abrasion yeilds sand from "lime sand brick" in your food. Trust me, you don't want that. I can't find it at the moment but, another builder figured that out for himself and tore down a half finished dome to start over with the proper brick. I have a couple hundred of them stacked out in my scrounged brickyard. You could possibly use them under your oven floor's primary insulation. However, I seriously urge you to not use them for the dome.

[polker8]

Thank you, So what I am thinking is , Storage heater bricks for the floor as i have these already and the the sand,lime bricks just for the arch/opening. The dome I will have to use the correct bricks or even clay mix

[UtahBeehiver]

How thick are the heater storage bricks, the ones I have seen used by the UK builders were about 25mm, for the floor you should have about 50mm so you may need to double layer if the 25mm version. The thickness gives you thermal mass or the ability of the oven to retain heat, too thin and the floor gets too cold to quickly.

[polker8]

The storage heater bricks i have are about 50mm thick and have a odd ridge on the back so i will bed them and a vermiculite mix first, I have enough to build the dome from them too but they will all need cutting in quarters and with the ridge they don't sit flat enough. I was thinking once the arch/door is built i will make the dome from a mix of clay and sand, then put an insulating layer on that and then render to keep the weather off. I know using clay is kind of cheating but i don't have any other option.

[UtahBeehiver]

Why not use a home brew for the dome, 3;1;1;1, sand, portland, lime, fireclay. vs just clay and sand? All fairly/readily available and cheap. Doing a cast dome over a sand mold. There have been several cast oven with home brew on the forum lately.

[polker8]

That sounds like a good plan if it will work, I was'nt sure if putting normal cement in the mix was a good thing but if others have done it then i guess it should be OK. Next mission now is to dig a big enough hole to get the clay.

[UtahBeehiver]

Do a search on homebrew on the forum. You will see a number of builds using home brew for both mortar joints and dome. I believe David S suggested that if you procuring you own clay, to snoop around where builders are excavating for homes and buildings. It will take a little prep work to get natural clay into a usable state. No mason or brickie suppliers on PEI or Nova Scotia?

[polker8]

I am kind of lucky in that my parents own a field where they used to make bricks and tiles from the clay so that should be the good stuff i hope, The wife and kids can do the mixing for me, haha. I will look up David s and have a look at what he has done, Cheers

[polker8]

OK, I tried to make the home brew mortar with clay i had dug up, I used the same ratio as mentioned just i used clay instead of dust, Was hard to mix it up and is really sticky but found that it cracks whilst it dries and doesn't seem to stick to the bricks, Think i will have to find a supplier of the powder

[Gulf]

You are probably doing right by finding a clay supplier. It doesn't sound like that you processed the clay that you dug?

[polker8]

Well, not sure about processed clay, but where i live if you dig down about 12 inches it is pure clay with nothing in it, ie roots or stone. I have built my door/arch with the bricks and used the home brew with the clay as mortar, so fingers crossed will see if it works.

[david s]

Whether the clay is purchased or dug from the ground, it must be powdered to make the particle size is small. It requires fully drying, pulverised to a powder and the sieved to further reduce particle size and removal of foreign material. This is what Gulf meant by processing.