are these the right bricks for a pizza oven?

these bricks are the best ones i can find where i live (venezuela), are they fine? (we call then rustic bricks). and i can´t find here any refractory cement or somethig like that, what could i use to bind the bricks? regular cement mixed with something else?

Those appear to be firebrick splits.  It's hard to tell but the graininess and scorch marks remind me of firebricks.  I think that would make a great oven!  I'm jealous of your find.

I am not sure how you should bind them.  I know in backyard metal casting, some people make their own castable refractory, which might work for you.  But all of the recipes I know use perlite.

The bricks look pretty good from what I can tell. All building grade bricks like this will start to fail if there are fast temperature changes, so if you use it, start with a small fire and work up slowly. Conversely let the oven cool slowly (another reason for that good insulation layer). The bricks will crack and crumble if the heat or cool too fast.
I would recommend against using regular cement. It will crack and spall with heat and time. It will them sprinkle your food with cement bits.
If you can tight pack the bricks in such a way that the mortar is minimally (almost not at all) exposed to the inside of the oven, I would use a clay and sand mixture. Research 'making cob' for instruction on how to mix it.

Rob Lineberger wrote:I think that would make a great oven!  I'm jealous of your find.

Ohh dude, those words really give me fate, it has been hard for me to find ways to make my pizza oven happen ;(

I was happy thinking that fiber glass would work as insulation, but that isn't the case... I can get fiber glass, but no ceramic fiber...

What about using rice husk instead of perlite in the recipe that you send me? Or on the recipes that you know that use perlite?

You can definitely use rice hulls mixed into cob as an insulation.  Its a great insulator in fact. Cob is basically clay dirt and sand.  

Rob Lineberger wrote:You can definitely use rice hulls mixed into cob as an insulation.  Its a great insulator in fact. Cob is basically clay dirt and sand.  

Do you think that i can put on top of that cob regular concrete so it has a nicer look and it is more resistant to the weather? In this way the dome will consist of 3 layers, the bricks, the cob with the rice husks, and the concrete.

Now that i am reading the "forno bravo" guide i think a can make the mixture for the binding of the bricks with portland cement, fire clay (i will try to get the clay they use for the bricks i found), lime and sand.

Doing that with the bricks the cob with the husks would only serve the purpose of insulation

Chris Sturgeon wrote:If you can tight pack the bricks in such a way that the mortar is minimally (almost not at all) exposed to the inside of the oven, I would use a clay and sand mixture. Research 'making cob' for instruction on how to mix it.

What do you think about this recipe from the "forno bravo" guide:

•1 part Portland cement
•3 parts sand
•1 part lime
•1 part fireclay (i will try to get the clay use to make the bricks of the pictures)

"Still, fireclay mortar is less heat resilient and thermally
conductive than a true refractory mortar"

Adding fire clay to any standard mortar will significantly enhance its capacity to handle heat.  

As for adding insulation, cob itself is something of an insulator, you just need to make it quite thick.  My cob oven is at least 8 inches thick, and thicker in some places.  On top of that, there's an inch of plaster to seal it.  All that mass heats up and then retains heat for a long, long time.  I used a high percentage of straw and sand in my mix, and the oven hasn't cracked.  I've heated it up REALLY hot and kept the temp super hot for 48 hours to fire the oven.  It got so hot that it charred the wood skirt around the outside of the oven and bubbled the paint on the boards, but the clay itself is fired rock hard.  

Marco Banks wrote:Adding fire clay to any standard mortar will significantly enhance its capacity to handle heat.  

As for adding insulation, cob itself is something of an insulator, you just need to make it quite thick.  My cob oven is at least 8 inches thick, and thicker in some places.  On top of that, there's an inch of plaster to seal it.  All that mass heats up and then retains heat for a long, long time.  I used a high percentage of straw and sand in my mix, and the oven hasn't cracked.  I've heated it up REALLY hot and kept the temp super hot for 48 hours to fire the oven.  It got so hot that it charred the wood skirt around the outside of the oven and bubbled the paint on the boards, but the clay itself is fired rock hard.  

That sounds really nice, your oven have bricks in the inner part of the dome? Could you tell me the proportions you used for your cob? It would be great if you post a picture!