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Post by cannyfradock on May 19, 2013 17:26:36 GMT
Alun.....love the snorkels. I should know by now exactly how many fire-bricks for every size of build....but I don't. Everybody's build seem to vary. On my last "Corrie" 90cm Pompeii build, my list was - 150 x 9" x 3" x 4 /1/2" fire-bricks (...had 30 left over)
- 20 9" x 1" x 4 1/2" fire-bricks (handy for arch transition and top of dome (10 left over)
- 3 bags powdered fire-clay (1 left over)
200 bricks sounds about right. Liam (kilnlinings) is very phone friendly. I don't think he makes much profit on delivery charges...he's just glad of the custom of selling his refractory products. Why not give him a call to discuss the delivery charge. I think he will try to keep the delivery to a minimum. Terry
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alun
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Post by alun on May 19, 2013 22:10:43 GMT
I guess I'll order about 200 and see how I go. Reading lots of people's builds it seems about right, especially if I don't taper all the bricks. I was thinking 2 bags of clay to make up homebrew. I hope this is enough if I am not tapering though (extra mortar needed). Ah I was looking at kilnlinings.co.uk/ceramic-fibre-blankets/cf-blanket-1260gd/cf-blanket-1260gd-3.66m-610-x-50mm-density-96kg for the blanket. I now see that this is the carcinogenic blanket. The one you linked to, while a bit more sounds much better to work with. I've already got 4 bags of Vermiculite (from Jewson) so I am set there. I'll definitely give Neil a call to discuss.
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Post by h12rpo on May 19, 2013 23:01:23 GMT
i only used one bag of fireclay, but I mixed up small batches and on chain 3 started to angle the cuts so as not to use so much homebrew. Cutting the bricks in half on an angle an then laying them on edge.
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alun
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Post by alun on May 26, 2013 12:01:36 GMT
Just took down the form work for my slab and noticed a few holes in the underside beneath the rebar: And a close up of the worst one: Should I be concerned about this? Will it affect the strength of the slab?
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Post by cannyfradock on May 26, 2013 16:16:21 GMT
Alun
That's a difficult one to call. The first picture looks OK. It seems like you didn't vibrate the shuttering when the slab was poured. (I gently tap the sides and the underneath with hammer....just enough so as air bubbles rise to the surface....other use things like an electrical sander with no paper to bring all the air to the surface).
The second picture however is cause for concern. Usually a few air bubbles won't hurt as the majority of the weight will be supported by the support walls or front lintel/arch. The decision to re-do the slab is a big one. WHAT WOULD I DO?.......if the problem was close to the side walls I may just repair by applying some acrylic primer to the problem area and fill with flexible tile floor adhesive....even if you have to apply 2 or 3 coats/layers of adhesive.This stuff sticks like sh*t to a blanket and hardens like iron.
If it's in the center (I know this takes the least stress, but it is the weakest point of the slab)....I may just build a 2 brick pillar directly under the weak point. That will give you "piece of mind...and it won't look out of place.
Terry
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alun
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Post by alun on May 26, 2013 18:03:20 GMT
Thanks Terry, Half of me wishes that I'd just left the plywood in place as others have suggested I had another look: Really annoying that a lot of it seems fine. I used a mallet on the form work to try and get air out. For some reason I didn't think about hitting the shuttering underneath! I'll do what you suggest with the tile adhesive. Hopefully that should hold the concrete together. Is the acrylic just to give the adhesive something to bond to? Also, a question about laying thermalite blocks on top of the slab. Do these go on a thin layer of mortar in order to level them out?
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Post by eddiej on May 26, 2013 20:44:02 GMT
On the plus side, at least you have put the steel in the lower section of the base, which is the correct position for 'tensile forces' which are the main requirement. The bottom of the base doesn't look pretty, but I wouldn't worry about re doing it. As a note.. Adding steel in the upper section is fine for compressive strength, but that is something that you don't particularly need to worry about as concrete has good compressive strength anyway. Placing steel in the centre of a slab does pretty much nothing from a structural point of view. This isn't a criticism of you or your hard work, but reading past build topics, I find it a bit of a shame shame that no one has ever suggested using a vibrating poker when concreting bases. I use them all the time, and they make life so much easier, and the concrete strength is increased dramatically. I also use fibre reinforced concrete a fair bit, but this would be getting a bit involved for an oven base, as it doesn't take much to bring the fibres to the surface, which would weaken the base.
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Post by cannyfradock on May 27, 2013 7:59:02 GMT
Alun
Nice to get a second opinion from Eddie on the slab. Your other pics confirm that although you could have vibrated the slab a little more, the overall result is OK.
The Acrylic primer is similar to uni bond/pva adhesive....except 10 times better....and yes, it's to give good adhesion to the repair. Use a small paint brush and brush the primer neat into the crack. Only put as much adhesive into the crack as per the bag instructions. (read maximum thickness etc) Normally this stuff is "rapid set" so the repair can be done in several seperate layers but within a short amount of time.
I lay my blocks on a full bed of normal mortar but only lay enough mortar for one block at a time otherwise the blocks may "float" when trying to get level.
Terry
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alun
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Post by alun on Mar 12, 2014 21:33:00 GMT
I've neglected this post for a loooooooong time. But thought it might be time to update now. I did manage to get the aerated concrete base in place and the bottom layer of fire bricks last year: This is from the beginning of June last year. However a number of things slowed progress after that. The amazing summer meant I spent too much time enjoying it rather than working on the oven and then the long, wet winter meant not much activity. I got a couple of rings in place before work resumed this year in February: Everything was a little mouldy and wet by this time but I think it will be fine. I built myself an indispensable tool and began working my way around the dome. I kept putting off doing the arch though as I couldn't quite visualise how to get it done: Finally, an arch!
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alun
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Post by alun on Mar 13, 2014 19:46:30 GMT
So those photos are all from a few weeks ago. With the good weather lately I've made a bit more progress: The arch transition is pretty ugly inside but it's all holding together and it is after all on the inside...hopefully no one will judge me too harshly. So far so good without any supports: and I've managed to tidy up above the arch. But now what to do? It's too vertical to just whack the bricks on and hope..... Of course! Exercise ball to the rescue. I asked my other half to pick one up for me (hence the colour): Also getting pretty dark. Time to stop for the night I think.
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alun
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Post by alun on Mar 13, 2014 20:13:42 GMT
And finally, last night the dome is complete! Quite a moment really. So, now what? I'm trying to figure out what the next step should be. Do I need to cure the over now or build the outer arch and chimney first? Any thoughts/experience very welcome.
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Post by cannyfradock on Mar 13, 2014 20:57:44 GMT
Alun These Pompeii ovens are quite a task to take on for a D.I.Yer......but many do. It's nice to see that you have completed the dome. The internal arch/dome transition is always a little head scratching but it looks as if you have done a fine job. I've just had a little look back at your slab and although you had a few air holes....it will be fine. You can start your "small" curing fires straight away, but I usually create my outer arch first. I use a mix of 1/4 and 1/8 bricks in the center of my entrance arch to form the vent for the oven.... ....I then lay on the thermal blanket and butt it up against the entrance arch. ....then a layer of chicken wire and on with the "devil's porridge".....vermecrete (vermiculite, cement and water mix) Terry
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alun
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Post by alun on Mar 13, 2014 22:54:02 GMT
Thanks for the reply and words of encouragement Terry. I'll get the exercise ball out next and touch up the joints inside as well as getting some photos. Then I need to get a few more firebricks down to have somewhere to lay the entrance arch. Unfortunately, I don't think I'll be able to make a thermal gap on the base due to the way the bricks are laid at an angle (and already extend beyond the inner arch) but I could put something between the inner and outer arch. I've seen a few people mention doing this. Something like www.amazon.co.uk/VITCAS-White-Stove-Rope-Replacement/dp/B0058TWJUW ?
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alun
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Post by alun on Mar 16, 2014 18:39:19 GMT
Well, it's not pretty: But I've since pointed it as best I can. The bit with the ball is nowhere near as good as the earlier rings. But at least you can't see them easily. I've now completed laying firebricks for the vent and oven landing and started planning the outer arch and vent: No thermal break on the hearth unfortunately but I'd like to do one between the arches. Was thinking about using some of the thermalite blocks cut 1 inch thick or so like this: but I'm not sure how to hold them in place. I'm guessing I'd need something with some elasticity to account for expansion in the dome? Also trying to figure out how big a flue I need.
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Bo
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Post by Bo on Mar 20, 2014 17:10:43 GMT
I created a thermal break using fire rope, think it was about 12mm, with a heat resistant mastic on top. My chimney is 5 inch diameter for a 36 inch oven..... Good luck.
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