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Re: Feeling brave... a true Neopolitan Pizza Oven
Hendo,
Brick depth on the dome and soldiers = approx 3", the hearth bricks are 2 1/8", which resulted from bricks that were locally available.
The buttress system is 5" thick. It is poured from a thick mixture of Kast-o-lite 22 (hereafter referred to as > KOL22), a 2200 degree insulating castable refractory. I debated going with a Perlcrete mixture, but since I was already placing a pallet shipped order for castable refractory (for the flue construction) and steel needles, I decided to go with Kast-o-lite on the recommendation of my builder contact. I suspect a Perlcrete or Vermiculite concrete mixed might reinforce in a similar manner, but it would need to have been tested and I wasn't in the mood to mess around with that. Beyond that, the idea is to keep heat in. The insulative value of Kast-o-lite products is way better than Perlcrete..
As I said, the KOL22 is 5" thick. It sits on top of the Insblok 19 (simply because I didn't want to run out by pouring it directly on the concrete slab.. wasn't sure I had enough) and the aluminum foil is only there to minimize the Insblok from sucking up the moisture from the wet Kast-o-lite mix till it cured.
Within the 5" KOL are 14" high pieces of 5/8" rebar that are sitting vertically in holes drilled through the Insblock down 2" into my concrete slab.... The rebar pieces are placed every 10" around the entire perimeter. Then several 4' long 3/8" rebar rods were bent to match the shape of the perimeter and placed and tied to the vertical 5/8" rebar pieces with rebar tie wire. If that weren't enough, I then took some extra 1" x 1/2" galvanized fence wire and wrapped that on the outside of the rebar... This whole reinforcing structure sits about 2" outside the soldiers (in the middle of the KOL22 pour...)... Once the rebar structure was in place, I used the same 1/4" fiberboard I used to support the sand dome (which bends really easily and is pretty strong) to create a form... I used L brackets and tap cons drilled into the concrete slab and the fiberboard to affix it in place along the bottom and a couple cargo straps to keep the form in place up top... I then mixed the KOL22 according to directions and poured.. It's a really thick mix, so read the directions if you go that way...
Yes, I think the vanes are polystyrene.. the are about 1/2" thick and available at Home Depot (our big home improvement store here in the states..).. you can buy 4'x8' sheets for about $8. These vanes were only used to set the arch and help maintain the arch as the sand form was being laid...
I wouldn't say knocking out the sand form was extremely difficult, but it wasn't a piece of cake either... Since the vanes are in there, you really have 4 sand dome quadrants if you will.. They tough thing about knocking it out is taking the bricks it's setting on out.. That sand form is heavy... Once you get most of them out, it just falls to the hearth floor and you can smack it around with some rebar or something and knock it apart in chunks... Others may have a more ideal sand/portland ratio.. I thought my ratio worked well.. It was soft enough to shave the shape as construction took place and hard enough to maintain shape under pressure and the repeated knocks of the end of my trowel against each brick as I placed it.. I suspect if you went too light on the portland, you have a less stable dome that might start to break apart as you bang your bricks in place... the challenge (for me at least was) the working time you have with Heatstop 50 (the refractory mortar).. the more it begins to set as you're working with it, the harder you have to bang your bricks in place for a tight fit and the more that sand dome needs to be able to stand up to it...
Thanks for the complements.. I'm happy to have gotten this far.. and again, I've learned a lot here and appreciate the advice I've received from some of the guys here along the way... My challenge is time.. I'm in software sales and I travel alot, so I don't get to work on the oven as much as I'd like... As I write this post, I'm sitting in a hotel room in Guanajuato, Mexico. Really cool town to visit if you ever get the chance...
JB
Hendo,
Brick depth on the dome and soldiers = approx 3", the hearth bricks are 2 1/8", which resulted from bricks that were locally available.
The buttress system is 5" thick. It is poured from a thick mixture of Kast-o-lite 22 (hereafter referred to as > KOL22), a 2200 degree insulating castable refractory. I debated going with a Perlcrete mixture, but since I was already placing a pallet shipped order for castable refractory (for the flue construction) and steel needles, I decided to go with Kast-o-lite on the recommendation of my builder contact. I suspect a Perlcrete or Vermiculite concrete mixed might reinforce in a similar manner, but it would need to have been tested and I wasn't in the mood to mess around with that. Beyond that, the idea is to keep heat in. The insulative value of Kast-o-lite products is way better than Perlcrete..
As I said, the KOL22 is 5" thick. It sits on top of the Insblok 19 (simply because I didn't want to run out by pouring it directly on the concrete slab.. wasn't sure I had enough) and the aluminum foil is only there to minimize the Insblok from sucking up the moisture from the wet Kast-o-lite mix till it cured.
Within the 5" KOL are 14" high pieces of 5/8" rebar that are sitting vertically in holes drilled through the Insblock down 2" into my concrete slab.... The rebar pieces are placed every 10" around the entire perimeter. Then several 4' long 3/8" rebar rods were bent to match the shape of the perimeter and placed and tied to the vertical 5/8" rebar pieces with rebar tie wire. If that weren't enough, I then took some extra 1" x 1/2" galvanized fence wire and wrapped that on the outside of the rebar... This whole reinforcing structure sits about 2" outside the soldiers (in the middle of the KOL22 pour...)... Once the rebar structure was in place, I used the same 1/4" fiberboard I used to support the sand dome (which bends really easily and is pretty strong) to create a form... I used L brackets and tap cons drilled into the concrete slab and the fiberboard to affix it in place along the bottom and a couple cargo straps to keep the form in place up top... I then mixed the KOL22 according to directions and poured.. It's a really thick mix, so read the directions if you go that way...
Yes, I think the vanes are polystyrene.. the are about 1/2" thick and available at Home Depot (our big home improvement store here in the states..).. you can buy 4'x8' sheets for about $8. These vanes were only used to set the arch and help maintain the arch as the sand form was being laid...
I wouldn't say knocking out the sand form was extremely difficult, but it wasn't a piece of cake either... Since the vanes are in there, you really have 4 sand dome quadrants if you will.. They tough thing about knocking it out is taking the bricks it's setting on out.. That sand form is heavy... Once you get most of them out, it just falls to the hearth floor and you can smack it around with some rebar or something and knock it apart in chunks... Others may have a more ideal sand/portland ratio.. I thought my ratio worked well.. It was soft enough to shave the shape as construction took place and hard enough to maintain shape under pressure and the repeated knocks of the end of my trowel against each brick as I placed it.. I suspect if you went too light on the portland, you have a less stable dome that might start to break apart as you bang your bricks in place... the challenge (for me at least was) the working time you have with Heatstop 50 (the refractory mortar).. the more it begins to set as you're working with it, the harder you have to bang your bricks in place for a tight fit and the more that sand dome needs to be able to stand up to it...
Thanks for the complements.. I'm happy to have gotten this far.. and again, I've learned a lot here and appreciate the advice I've received from some of the guys here along the way... My challenge is time.. I'm in software sales and I travel alot, so I don't get to work on the oven as much as I'd like... As I write this post, I'm sitting in a hotel room in Guanajuato, Mexico. Really cool town to visit if you ever get the chance...
JB
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