clay bricks in a wood fired pizza oven

the home brew refractory cement and cast-in-place-dome themes of the last posts by damon and trav got me thinking...

if the mix suggested in damon's link works, it should be pretty straightforward to pour over a sand dome. i reckon id use some sort of reo as well - in a shell probably 100mm or so thick, but i wonder if there would be any problem with different rates of expansion between the cement and steel causing cracking/failure of the structure?

if you're going to cast cement or lay bricks over a sand core, use some sort of interface breaker. when i dug out the sand core after laying the bricks of my dome, some of the sand was stuck to the mortared joins. i reckon this would be much worse if the whole dome was cast over the sand. this then proceeded to rain down from the roof of the oven for some time. crunching sand in your teeth in the middle of a mouth full of pizza is a bit like finger nails on a blackboard. nasty

i dunno - maybe laying builders plastic or something over the sand before hand will stop sandy pizzas

apologies for starting to monopolising this discussion, people :-. since its his thread, hopefully at least trav and some of the rest of you are finding this useful...

anyway, some further thought on the home-brew mortar i mentioned:
the arch section of my dome was mortared in place with some home-brew refractory mortar and i did the hemisphere at the back with a tub of the pre-mix i mentioned earlier. while the home brew seems to be holding up (pun intended) fine, im not sure id recommend the mixture i was advised to use at the time.

it was suggested to me that the inclusion of lime (afaik, in brickies mortar to clag it up a bit for workability and to slow down the curing reaction of the cement) and clay (the red component of brickies sand) would be no good at high temperatures. i dont really recall the reasons why. the suggestion was that i should only use refractory cement and washed sand to make a properly temp stable mix.

im guessing now, but i suppose i might have used something like a 5 or 6 :1 (s:c) mix. anyway, an initial test with a small batch confirmed that it would actually bind to bricks when cured, but with no lime or clay present, it was terrible to trowel up.

cant really see what the problem with lime would be...

Have done a few pizza ovens and my preferred bricks are solid white or cream clay pavers 230 * 110 * 40 mm as these are easier to roll the dome over as they are only 40 thick and being solid have better insulation properties . I also like to use a triple layer in the base with the top layer dry laid (no refractory cement ) as they can be easily replaced if necessary. When u place sand to form the dome throw in a few 8 " concrete blocks to help fill the void ( you will appreciate this when u have dug out the 3rd wheelbarrow full of sand ). Some like to spread cling wrap over the sand to prevent sand getting in the mortar joint . The only measurements I have found of importance is the opening height of the door to be 3/5 ths the internal height of the dome e.g. door height 300mm / internal height 500mm. Any other questions please ask ,not guaranteeing i have all the answers though. , regards

First post - hi ewverybody!

Quote:

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Originally Posted by Trav

I'm thinking of using old shelves from a proper pottery kiln for the bottom, sitting on top of a thick concrete slab.

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Hi Trav - don't do this (use an old shelf) - pottery glazes use some pretty nasty heavy metals etc in their makeup that are fine in pottery, but I wouldn't be cooking anything on them, just incase it gets into the pizza.

Still, reading about it is making me hungry. :)

I'm interetsed in building a pizza oven and had been thinking of using secondhand bricks from an old fireplace/chimney, would these be suitable to use for making a pizza oven

Tx

Bob K

Realistically most bricks have been fired at near 1000 degrees , the most your electric oven will go to is around 280 degrees . The most your domestic pizza oven will be is between 180 and 250 degrees ( have a wireless weber thermometer in mine ) so the bricks will not be the first point of failure . The biggest mistake is to use a cement rich mortar free of limil as this is too brittle to take the variation in temperature , regards

Just spotted this post. I have posted a couple of photos of my nearly finished oven under the cooking section. Insulation & waterproofing to go on yet. Floor & dome made of solid house bricks & has handled the heat so far after 6 firings. The bricks in the external brick work are left overs from the house & very much seconds and this is second time I've tried brick laying, maybe I'll use a level next time.:B

Wish I'd built it years ago.

Regards,
Ray