30" Pompeii in Minneapolis

[RandyJ]

Wow sounds like a great plan. I can't wait to see it when you are done. The fund raising event sounds like a fun time. How many people are you expecting to have for it. The most pizzas I have done so far is 16. But if I kept it simple and had a helper I could maby see doubling that with out to much effort. Good luck. It is looking great.

Randy

[gastagg]

Thanks Randy! I put a lip on the front edge to minimize smoke escaping from the front too. I plan to make it all the same color. Going to stucco out the entry arch and then put a final layer on the whole oven. Then I'm going to use a Behr stucco product to seal and give it a consistent color. I have a fund raising party for the performing arts program at my daughters high school on May 21 so I hope to have all things done by then. Stucco paint requires 1 month before applying on fresh stucco.

[RandyJ]

Hey that turned out very nice. I bet you are happy to have that fixed now. It will look very nice with the stucco. Are you going to make it all the same color? I can't wait to hear how it draws. My guess is very good.

Randy

[gastagg]

Pulled the forms today. Am pleased with the results. Soon as I get some warm weather for a few days, going to put on a layer of blanket, install metal mesh, and then stucco. Thanks for the help Dave. I'll be honest with you all...if I were doing this again, I'd build a cast oven.

[gastagg]

Ended up using the polypropylene fibers and not the metal ones. Minimum wall thickness is 2".

[gastagg]

Thanks Randy...took a lot of rubber mallet beating to get the cement down into the form . I tend to error on the side of less water. Most of the seams have some stuff squeezing out a bit, so I'm very hopeful that it will come out OK. Got a heater under the wrap for the next few days to keep it in the 40s in there

[RandyJ]

It is looking great. I can't wait to see how it turns out.

Randy

[gastagg]

Bolt hole jig for the chimney mount...we'll see how this turns out next week.

[gastagg]

Replacing the entryway arch...

[david s]

Wow, thanks for the information Dave. How much SS fibers? How much polypropylene fibers?

A min of 2% by weight of the dry castable mix for the stainless steel needles. Their real name is stainless melt extract fibres by the way.
Only around half a handful of the polypropylene fibres for your casting, but you need to mix the brew about double the time that you would normally because they take more time to dispers properly.

[gastagg]

Wow, thanks for the information Dave. How much SS fibers? How much polypropylene fibers?

[david s]

Dave, what is the recipe and ratios for refractory concrete? I've seen (3) sand, (1) lime, (1) portland, (1) fire clay, but that's the same I used for the mortar. Also saw that I need to add some stainless steel needles or something like that. Thanks for the help!

I use a proprietary castable refractory (calcium aluminate cement), but if you use a home-brew castable it should be adequate because the entry does not see as much heat as the inner dome. The home-brew mortar recipe (3:1:1:1) is already very rich in active ingredients (cement and lime), some folk recommend a much leaner brew for mortar, but as some of the portland cement will degrade the lime remains to act as the "glue". The clay content can be considered a very fine aggregate so you end up with a 2:1 ratio of aggregates and cements, so don't go any richer. Unfortunately the home-brew does not contain any burnout fibres like proprietary castables which gives a measure of protection from steam explosions for thicker pieces so these should really be added. You can use polypropylene fibres available from concrete specialist suppliers. Don't bother using chopped up fibres from polypropylene rope.. I've tried experimenting with it and found that because the fibres are much thicker they melt at a higher temperature (over 160 C) which is too high to allow the passage of steam through the casting at lower temperatures. The ones you want are finer than a human hair. Stainless steel fibres can also be added to give the casting extra strength. If I were attempting a casting with home-brew and no stainless reinforcing I'd be using no less than a 2" thick casting. With fibres 1.5"

[gastagg]

Dave, what is the recipe and ratios for refractory concrete? I've seen (3) sand, (1) lime, (1) portland, (1) fire clay, but that's the same I used for the mortar. Also saw that I need to add some stainless steel needles or something like that. Thanks for the help!

[gastagg]

Thanks Dave. I'll make the adjustments. How thick should I make the casting? Here are some pics of the teardown of the old entry arch. It was in about 6 pieces. You can see the ice in the pics.

[david s]

Starting on my cast entry arch and vent. Here is a pic of the foam form I'll use to build the full form around. Quick job with a 1 1/2" 4'x8' sheet of foam board from Home Depot. Snowed today...next week is supposed to be above freezing. Hopefully get some work done outside next week.

George,
The casting will be stronger if you eliminate sharp edges and corners. You can then make your casting thinner. It will also improve the flow of the smoke.
Dave