28" Pompeii

[ggoose]

Re: 28" Pompeii

Today I set the hearth insulation and cut and set the floor bricks. The floor was a little trickier than I imagined, as the fireclay mortar sets up pretty quickly. If you have to adjust the layout once you begin you basically have to pull the affected bricks and re-butter them, as the insulation wicks the moisture away from the mortar rather quickly. I guess it took me about an hour, and I ended up with a few edge joints a little wider than I would have liked. A little sand should take care of that.

Tomorrow I will try to set the first course of oven dome bricks. Question for those who've been there/done that: do you fireclay-mortar the bricks to the hearth insulation and refractory-mortar them to each other (the sides I mean)? Or do you just set the dome bricks right on the insulation and call it good? My insulation seemed a bit uneven from the manufacturing process, so I thought a bed of fireclay might even things out, but that would mean two different mortars going at the same time

By the way, my 28" pompeii has grown to a 32" pompeii...must be all of the rain

[ggoose]

Re: 28" Pompeii

Thanks John; sounds good. I'll likely begin the mortaring tomorrow. I have to get some sort of cover to protect the build from the elements and tree pitch until I get a roof over it.

[GianniFocaccia]

Re: 28" Pompeii

Gene,

Nice-looking start to your inner arch. Love the angled bricks! The toughest part will be maintaining the inside arc to the arch while keeping the outside (flat) brick faces plumb and flush. This is where patience is a virtue. I recommend cutting your center arch brick first (match this brick's inside face to your dome template) and then scribe a circular line (indispensible tool) down the top of this brick to your outer-most arch brick. This will give you the inside arc you need.

John

[ggoose]

Re: 28" Pompeii

I have pulled the forms from the hearth and am fiddling around with the dome-to-arch transition, cutting the bricks ahead of time. I am hesitant to make too many cuts on the dry run before actually setting the bricks with mortar, as the gaps will most likely increase with the addition of mortar and render the dry run cuts inaccurate.

[GianniFocaccia]

Re: 28" Pompeii

Gene,

Sounds like you are on your way and staying ahead of the weather!

I have never rented a saw, but be aware that rental yards make their money on blade 'wear', which they measure, not you. In every case I have heard of, the charges for the amount of wear you incur are excessive and can almost pay for a brand new blade.

John

[ggoose]

Re: 28" Pompeii

Thanks for the input guys.

The homebrew sounds like a good alternative. I priced the FB mortar and it is $50 plus about $40 shipping to my area. I do like the fact that it contains no portland cement, and even with shipping is considerably cheaper than Heatstop (~$120 w/tax around here).

I just received my FB insulation today, so as soon as the rain stops in the next few days I can set the hearth insulation and begin the firebrick work. I have been working on the dome-to-arch transition in my garage and I think I may rent a 14" brick saw to cut the tapers for the top of the arch. My 10" saw (and my proficiency level) aren't cutting it, so to speak.

[AtTheLake]

Re: 28" Pompeii

I also opted against the Sairset and went the Homebrew route. (Changed my mind in the store after I already ordered it). So far the Homebrew has been great. Dries rock hard and impossible to get bricks apart after a week of curing.
I bought "Miracle Hydrated Lime" from the local masonary supply house. Lowes also carries it. With a name like that it has to be good. For sand I am using the fine silca sand from Home Depot. For fireclay I bought #20 and #30 from the refractory supply house. I have mostly used the #20.
One nice thing about purchased fireclay verses the stuff from your saw is that it is perfectly dry so I can premix 50lbs of the dry mix in a large tote and then just mix up small batches with water as I need it. This also keeps your mix very consistant.

Dino the refractory store sells bags of the firebrick chips for exactly that (large gaps). They called it "Grog"

[GianniFocaccia]

Re: 28" Pompeii

Gene,

I'm not too knowledgeable on lime although I went with the Type S hydrated lime. Here is a brief analysis of the different types of lime. It appears the difference in N and S is in it's compressive strength.

http://www.lime.org/documents/publications/free_downloads/fact-masonry.pdf

My silica sand is #120, mixes up in the homebrew recipe like butter and cures out really hard. Two notes on my application of homebrew: the outside joints that are closer to 1/2" (first eight courses) show no cracks at all. The last few courses, though, are just under 3/4" and a few really tiny hairline cracks (maybe half an inch long) have appeared. I would consider mixing in some #60 silica sand if your outside joints are going to be larger than 1/2". This is because portland shrinks as it dries and larger pieces of aggregate minimize shrinking.

I have been extremely lucky with drizzly (is that a word?) weather during my build and I have not had to drape a wet curing towel over set bricks except a couple of times.

Fireclay - It believe it is optimal to use the clay dust from your brick cutting to 'match' the properties of your firebricks. I have intermittently added my own harvested brick dust to the mix but more regularly used 'mortar clay' I bought in a 50# bag (H.C. Muddox) because of convenience. Over the course of my build I have wondered (but that's all) how effective it would be to mix very small firebrick chips as aggregate into the mortar that goes into the outside of the joints.

John

[ggoose]

Re: 28" Pompeii

I have been perusing threads on homebrew, but can find nothing on some of the specifics...

Lime: quicklime or hydrated? If hydrated, Type N or Type S?
Sand: I have seen reference to 60# and 120#, and silica for the sharp edges. Is this a good sieve range?
Fireclay: This seems like a gereric term; what should the minimum aluminum oxide content be (or does it matter)?

Sorry for tha barrage of questions, but at this point I get the feeling that I don't even know what I don't know

Thanks again for any replies,

gene

[ggoose]

Re: 28" Pompeii

OK John and dmun, thanks....homebrew it is.

[dmun]

Re: 28" Pompeii

It is good to about 3000 degrees F.

That's the key. This stuff is made for applications like boiler fireboxes and blast furnaces, where there are small, tight joints between the firebrick, and more important, are fired to high temperatures. At the temperatures that ovens work at, most of the wet pre-mixes aren't hot enough to "heat-set", and remain subject to problems with moisture.

I used heatstop, which is a dry mix that's air setting, and if I built another oven I'd use the home brew.

[GianniFocaccia]

Re: 28" Pompeii

Yup, Gene, homebrew does contain portland. I questioned this recently and was told that the portland is used only as a 'gauging' material when aligning one's bricks in each course. When the portland 'burns out' the lime takes over and actually grows stronger over time. In the traditional 3-1-1-1 homebrew recipe, portland comprises 16% of the overall mix.

Can't say I've ever heard of Adamant X, but you can't argue with proven results. I'm not sure a 3000F mortar is optimal for our application, but I would side with Millstone Man, it's been recommended to stay away from the wet premix. My homebrew has been nothing but a joy to use and very inexpensive since I was gifted 400lbs of #120 silica sand and two 50# bags of portland.

John

[ggoose]

Re: 28" Pompeii

I considered the homebrew Scott but I was reading that portland cement degrades and even fails at high temps; doesn't the homebrew contain portland cement?

[Millstone Man]

Re: 28" Pompeii

Gene - Most of the stuff I have read here discourage the use of the wet stuff sold in tubs or pails. Go with the dry mix or better yet use the home brew as it really is not that hard to make and use. I used the dry bags of Heat Stop 50 but would use the home brew if I had it to do over.

[ggoose]

Re: 28" Pompeii

Thanks John,

In that case, I think I'll pass on the Sairset. I spoke to a couple of brothers today at the local brick store who showed me pictures of a Pompeii they built for a client in 3 days...it was a work of art...brick cuts included; they looked as neat and clean and symmetrical as yours. They used a mortar called Adamant X. It is good to about 3000 degrees F. I still need to talk to a sales rep about it, but I will ask him if moisture affects its performance. Have you ever heard of it? It is very old school; recipe is circa 1907-ish. It is wet and a 55# bucket goes for about $50. We'll see.

gene