42" Pompeii at the Concrete Casa

[ThisOldGarageNJ]

Re: 42" Pompeii at the Concrete Casa

hey mich,

That vermicrete is odd stuff

Indeed, keep in mind vermicrete has no structural strength, only compressive strength... So... when your done curing it, and you take off the form, the sides may chip or crumble a little,(thats ok), but you could probably stand on it with no problem... your pics are looking good.. you'll be laying rick soon... I did use a full brick for my soldiers,,cut at 17 degrees it saved me from cutting one row of bricks, other than that I think its just personal preference on how you do it..
Cheers
Mark

[michaewa]

Re: 42" Pompeii at the Concrete Casa

Had a good weekend and made some good progress on the oven.

Got the floor laid out and cut before I realized that it was running bond and not herringbone. I'm not going to worry too much about that.

Also got the soldiers cut and the first row above them cut and dry stacked. Agonized about the angles, etc. and then I just started cutting and it was much easier than I was making it out to be.

I also fashioned an 'indispensable tool' using the simplest means I could think of. I took a simpson bracket, a length of square tubing, and a hinge. Attached the bracket to one end of the rod and the hinge to the other end using JB Weld. I attached the hinge to the center of the protective overlayment so the pivot point is 2 3/4" out from true center. I wanted a radius 2" larger than the height (19" dome height and a 42" oven), and my protective layer plus hinge assembly raises things 3/4" off the true oven floor.

We'll see how my math turns out, but it seems to work on paper. As with drseward's oven, it should be intersecting ellipses and I'll try and finish the apex with a flat(ish) plug.

I'm planning to lay the superIsol down in the next day or so, and was considering wrapping it with either plastic wrap or aluminum foil to keep it from soaking up the water from the sand+fireclay leveling mixture. Any thoughts on if that is even worth thinking about? I am a bit concerned about getting it soggy right off the bat.

[cannyfradock]

Re: 42" Pompeii at the Concrete Casa

Hello michaewa

Have been following your thread from the beginning and am waiting with baited breath for each installment of your progress. I apologise for calling you a proffesional in my earlier post, but I don't apologise for saying that your proffesional approach and articulation in your project is very commendable. Your last post in particular seems very methodical in it's precision of calculations.

Shall keep following this thread (If I may) and look forward to seeing your "in-progress" pics

Regards Terry (C.F)

[michaewa]

Re: 42" Pompeii at the Concrete Casa

Thanks Terry!

It was very nice here today, so I decided to try to lay the insulation boards down and was planning to set the floor after that.

I was using the sand + fireclay mixture and I'm pretty sure I had one or more of the ingredients wrong. The mixture didn't 'mix' well - even after several minutes with a power mixer the water just floated on top and the solids precipitated out. When I scooped some out and put it on a mortar board, it was completely runny, but when it touched a surface (e.g. the vermicrete layer or the insulating board I set in the middle of the vermicrete) it immediately balled up. Any attempt to spread it with a notched trowel just dragged the whole mess around.

I ended up just kind of sprinkling it around by hand and got the insulation boards relatively level, but gave up trying to set the bricks.

For the fireclay I just stretched a t-shirt over the top of a bucket and poured the tray from the wet saw into it to catch the solids. The sand I used was silica sand, as that was the finest I had around.

I've seen some suggestions (dmun, I think) to skip the water, which I may try next. If anyone has any feedback on the clay or the sand I used, let me know.

[dmun]

Re: 42" Pompeii at the Concrete Casa

The dry mix was the original idea of Alf, from the UK, who said that the dry mix let you pull up and fix any unlevel bricks. When you're satisfied with the results you can wet the floor to solidify the mixture.

The firebrick cutting slurry may be less fine than fireclay in the bag: that may be why you're having trouble.

[michaewa]

Re: 42" Pompeii at the Concrete Casa

For anyone reading this, I highly suggest using the fireclay / sand mixture dry. Infinitely easier. I re-leveled the insulation boards and then set the bricks in a very thin bed of the dry mixture. The only downside was the wind caught one of my insulation boards and it broke in half when it hit the ground. It was a clean break though and went back together just fine.

I figured I'd kill two birds with one stone, and used my wet polisher to touch up the surface and to get the bricks wet to hydrate the fireclay / sand mixture. It worked well - the last counter top I polished had dark grey pigment in it and a bit of that was still in the polishing pads, giving my oven floor an instant 'antiqued' look.

The floor isn't perfectly level as there is a fair amount of variation in the size of the bricks in all dimensions, but definitely tolerable. I figure if there are offending edges I can always get in and grind them further later.

I laid out my indispensable tool and dry stacked the soldiers, it looks like it will take a few courses before I 'catch up' from the height of my soldiers so that the bricks will align just right with the tool.

I have a few materials questions hopefully someone can weigh in on. My local dealer carries Alsey products, and when I asked for high temperature mortar for my application, he brought me Alsey Air Set Refractory Fireplace Mortar. I'm assuming this is not correct, as it says on the bucket it shouldn't be used in outdoor applications due to humidity problems.

I also got a bag of what I think was fireclay - when I initially asked for that he told me that the air-set was fireclay, but eventually ended up bringing me a 50lb bag from Alsey that doesn't have any product name on it. It looks like this, but without the 'DMFC' label on the front. He indicated it was fireclay but I just want to make sure.

I'm guessing I need to either go the homebrew route or try looking by brand name for HeatStop or RefMix?

Cheers!

[dmun]

Re: 42" Pompeii at the Concrete Casa

I don't know the Alsey line, but builders have repeatedly reported trouble with the pre-mixed wet refractory mortars, they don't hold the bricks very well, and they don't set properly. The stuff also has to be very fresh. If it's at all shopworn, it won't spread properly.

My take? Why pay refractory mortar prices for water?

[michaewa]

Re: 42" Pompeii at the Concrete Casa

Ugh. Sourcing mortar is turning out to be the long pole in this process. After dozens of phone calls and emails it seems my three options at this point are to go with HeatStop 50 or the FB Mortar or to homebrew. I am not crazy about the homebrew course given what I've read about the effects of cyclical temperature on portland. However, to get HS or FB mortar shipped to me works out to just over $100 / bag including shipping. Somehow when shipping is more than the product I'm motivated to find alternatives.

I travel around the midwest a bit, does anyone know of any suppliers in MO / KS / NE?

Although we've had quite a cold snap here lately, I find I keep going outside and looking at my dry stacked bricks dreaming of having a handful of refractory mortar

[dmun]

Re: 42" Pompeii at the Concrete Casa

If you can get extra fine sand, it seems the homebrew works fine. The portland acts as a binding agent where it doesn't get so hot, and as an aggregate to the lime where it doesn't.

[ThisOldGarageNJ]

Re: 42" Pompeii at the Concrete Casa

ask james...
he was going to check how much mortar he could ship in a USPS flat rate box, It might work out cheaper that way...


Mark

[michaewa]

Re: 42" Pompeii at the Concrete Casa

Thanks very much for the feedback. I checked with James and there wasn't much in the way of cost savings for the flat rate box.

I decided to start with the homebrew and see how things go. I have all the materials, just waiting for a day above 40F to start setting the bricks.

Until then my wife is perfecting her dough recipe and we are falling back to the pizza stone in the indoor oven...

Cheers!

[michaewa]

Re: 42" Pompeii at the Concrete Casa

Finally back to this after a long cold winter and a slew of other projects. Worked yesterday and today and got the soldier course and the next two rows, as well as the inner arch done.

Here are some pics from the end of day one.

[michaewa]

Re: 42" Pompeii at the Concrete Casa

And from the end of today. I set the outside edge of my inner arch even with the reveal for the door. I haven't really thought through how this will look in the next step. Hopefully the pictures will illustrate, let me know if that doesn't make any sense.

Any suggestions?

My thought is that can have the next arched row sit 1/2" higher than the inner arch, and that would be the door stop. I've yet to grok the size of the vent opening, my head hurts just from getting the arch done.

Cheers.

[KraemerBAC]

Re: 42" Pompeii at the Concrete Casa

Looking good,

I have the same thoughts for my outer arch....I don't see why it wouldn't work just fine. The only adjustment will be for the chimney mounting plate

Peter

[Jon in Albany]

Re: 42" Pompeii at the Concrete Casa

Michael-

I'm new here so I lurk, watch and learn most of the time. Honestly, a glass of Scotch and a good build thread with pictures is all the entertainment I need for the night.

In looking at the pictures of the round piece protecting the floor and supporting the Indispensable Tool, I don't see any seams. I just want to make sure you had an easy way to get that out once the dome was closed.

The arch looks good to me and I'm enjoying your thread. Please keep up the pictures questions.

Good Luck.