28" Pompeii

[ggoose]

Hello Everybody,

I'm happy to say the weather has finally allowed me to commence my oven build. I have been lurking and learning on/from this forum now for many months and will say in advance "Thank you" to all who contribute to it. This is not something I would have ever thought of, much less attempted, were it not for this forum (and website in general), and its host and contributors.

I have to build a smaller oven than I originally planned due to an existing slab pour, which I extended. I didn't want to widen it to accomodate a larger oven because I thought the resulting triangles on either side of the new slab might fail, as they would be weak points, or at least to my thinking they would be. Some here suggested I extend the hearth beyond the block walls (as has been done on other builds), but that is not the look I want, even though it is a valid means of increasing the oven size.

These first few photos are pretty standard. My next step is to form the hearth and arch above the wood storage door, add rebar, then fill the cores. I would like to pour the cores and hearth slab together, but I calculate it will require upwards of 50 sacks of 80# concrete mix do do the entire pour, and I'll be doing this solo, so two pours is most likely.

gene

[Lburou]

Great start!

Your work site is uncluttered. Your work very clean too. Something I haven't mastered

We have a new concrete business in our neighborhood. Its a mobile concrete truck where he mixes what you need right on-site. No minimums, up to 7 yards......You may have one of those on-site mixing trucks available to you. It won't cost any more than the sacrete and will be much faster and a potential better quality concrete overall.

All you need is a wheel barrow and shovel.

Just a thought.

[ggoose]

Re: 28" Pompeii

Thanks for the input Lburou. We have those same trucks here; in fact I used one to pour my footings and stemwalls for my garage. Unfortunatley, here they charge $150 for a "short load", anything less that 4 yards. So it is a bit cost prohibitive.

gene

[GianniFocaccia]

Re: 28" Pompeii

I thought the resulting triangles on either side of the new slab might fail, as they would be weak points

Question for the concrete/construction guys out there: In Goose's build, if additional triangle slabs were poured adjacent to the main slab, how much strength/rigidity would a CMU wall with horizontal rebar contribute to the entire unit, if any?

If this would not be the prescribed method of enlarging the slab, what would?

Great start to a very promising project, Goose.

John

[ggoose]

Re: 28" Pompeii

I was able to finish forming the hearth and installing the rebar today between rain showers.

It looks like the manual method of pouring the concrete will be to mix it in a rented mixer, dump it into a low trough (like a mortar tub) because that is about all one can dump into from the mixers Home Depot rents. Then shovel the mix from the tub into the cores/hearth. Does this sound about right to those who have done this before using a low-standing mixer?

gene

[GianniFocaccia]

Re: 28" Pompeii

I used a Harbor Freight mixer, but yup, that's the process. I didn't use bags of premix, rather I measured aggregate/sand (blend) mixed with portland and water by hand (bucket). It was a tremendous amount of work to do by myself, but the mixer, wheelbarrow and shovel was the ticket. Based on your pics, you're ready to go.

John

[Les]

Re: 28" Pompeii

. Then shovel the mix from the tub into the cores/hearth. Does this sound about right to those who have done this before using a low-standing mixer?

I don't recall who it was but someone built a scaffolding and placed the mixer up high. My mixer allowed me to empty into a wheelbarrow and I shoveled from there.

[ggoose]

Re: 28" Pompeii

I am to the point of purchasing hi-temp mortar, and the local supplier sells a 15# pail of HeatStop for $32 and a 55# bag of Sairset for $67. Apparently both are already premixed with water. Has anyone used Sairset before? It is supposed to be good to nearly 3000 degrees F. I am a bit concerned about a wet mix in a bag that dries with air contact...I don't want to open the bag and have to use it all immediately. If anyone has experience with this product: did you like it and would you use it again? How did you seal the bag so the remaining contents didn't set?
Thanks for any responses,
gene

[ggoose]

Re: 28" Pompeii

Thanks John and Les,

I ended up doing it with a mixer and a tub and a shovel. Worked fine but made for a bit of a long day. I figure I moved about 40 bags of 80# four times (from HD to the truck to the mixing site to the mixer to the forms). I'm curing the hearth with plastic for a week or so until my FB insulation arrives and I can commence the firebrick work.

[GianniFocaccia]

Re: 28" Pompeii

Goose,

Sairset is a Harbison-Walker product. I believe this is the wet equivalent of the dry refractory air set mortar (Sairbond) I purchased from the HW warehouse in Los Angeles for $37 for a 50# bag. Instead of using it on my oven (I went with homebrew mortar), I built a firepit with it. It was easy to work with and the firebricks held beautifully over the course of a dozen or so fires. Unfortunately, the distribution manager who sold me the Sairbond forgot to mention that the mortar was water soluable. Even though it was covered, the humidity from the next rain turned my mortar to dust. I am now faced with rebuilding it using homebrew mortar. Don't know if it was just an old bag of product or what, but I am pleased to no end that I didn't use it on my oven.

John

[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

[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

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?

[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

[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.