Spinal's Londinium Build

[spinal]

Bob - that comes from Gambia, West Africa. I lived there for a decade or so; and the local artisans make pots out of old soft-drink cans.

In return for a couple hundred empty cans and a few pounds, they smelt down the aluminum and give you a nice pan! I was so impressed I brought one back (there's a lid around the garden too...)

M.

[turkey]

haha I did think about your 56k when I saw the pics bob :-)

I see what you mean on the brick types. Personally due to the side forces I would do soldier as you need the structural support and really heat is critical above and below not from the sides really, although I am mostly going on the photos from FB. I nearly cut my bricks into thirds to make the dome heat quicker, it would be interesting to see how that kind of thickness works. Or you go sailor and skim it with refractory cement to hold it all firm. Then its wide enough for a angled half brick to start the dome arch off.

I like the idea on vermicrete to brace the walks. The FB build seems to stand ok but I would want dome extra reassurance if it was me. You could also sink a couple of rebar rods into the hearth, best to encase them in insulation so they are not heatsinks.

really loving this new style to the forum :-)

[spinal]

Hmmm... may end up doing a sailor course... tbh, I'm a very visual person, so until I get the bricks and start playing with them, I wont be able to decide what to do! (unless I can find some lego's to scale... )

I did think of some rebar, originally between the concrete and the vermicrete - to hold the two layers together... then decided it would act as a heat-sink and move heat away. That said, if they're insulated...

On a side note, any idea where I can get some HAC in the UK? The only place I can find (online) is travis perkins, and I don't have an account there... planning to use 3:2:1 (sand, fire clay, HAC) instead of the 3:1:1:1 recipe to avoid using portland and to get some more aluminum into the dome... again, in the interest of getting it hotter faster...

M.

[cannyfradock]

M

HAC or Ciment Fondue as I know it can be ordered in, in most builders merchants. Many others stock it....I believe "Wickes" do.

Even though the aluminium content is higher, I can't see (for the amount used) much difference in the refractory qualities of a homebrew made with either HAC or Portland cement. I would also keep to the same mix and ratio....i.e 3:1:1:1 .....sand, hydrated lime, powdered fire-clay and cement. The only time I would change this ratio is when the sand is fine...or very fine. I would then up the ratio of the sand to 4,5 or even 6 parts depending on the size of the sand grain.

The HAC tends to go off very rapid and I would only use it when using a jig where 1 brick at a time is laid and left to set before laying the next.....and then, mixed only in very small quantities.

Terry

[turkey]

would Jewsons not be able to get a bag or 3 of it in?

I like the thinking although have no idea if it would make a real world difference, but also agree fast setting means small render mix's more often. Not so bad if you have a willing helper tho

[spinal]

cannyfradock: Using lime and HAC isn't a good idea, while a retardant and plasticizer for portland, with HAC it speeds up the reaction. Mixing 3111 with HAC will end up with a mix that sets in 10 minutes or so... which is far too fast for my slow hands I'm led to believe that a 321 mix should set in 20-30 minutes, depending on weather, which is perfect for me as I can get a pseudo-willing helper to mix while I lay... by the time one ring is done, the mortar should have set enough for the next ring...

Wickes - asked, couldn't find any on their system. Since it's been banned in the UK for structural buildings, it's pretty hard to find...

Jewsons - they need an account too, don't they?

M.

[turkey]

Ahh young padawn, more forum searching for you ....

we have a forum Jewsons account

this should get you about 40% off their high "retail" prices for building materials. Double check the costs of things as it still may not be the cheapest, but it has been quite useful for many folks.

[cannyfradock]

I've never used this HAC/Ciment Fondue/rapid drying cement (I beleive they all have the same qualities) in oven building as I've always used a form. I have used it "on site" however, for rapid repair of masonry in emergency situations. It doesn't matter what the weather is like. Once water is added, it starts off the chemical reaction and the mortar will quickly become warm or even hot and set rapidly. This is only a guess but if retarder is added it may have an adverse affect on the mortar and even crumble after drying.

I think ciment fondue is a "Lafarge" product .....if that's any help.

It sounds like you are rapidly approaching the dome build so just in case you can't find it....here's the link that Turkey was talking about.. ukwoodfiredovenforum.proboards.com/index.cgi?board=membersdiscounts ....hope it helps.

Terry

[spinal]

Great - thanks Found the Jewson's account too. That's spectacular, planning to call them today to see if thay can beat my £11.something per bag (100l) of vermiculite.

Dome will be a while - planning to do the vermicrete layer, covering it all up with plastic and taking a break while I order vermiculite boards, firebricks and fire clay... This should also help the concrete set (been watering it 3 times a day so far) as it'll be 2 weeks or so before I do any more after the vermicrete...

Planning to lay the board and floor bricks in one day, and then cover again for a week or so while I decide what to do heighwise...

Forgot to say, both lafarge and castle do (or did) HAC... problem is, most places just stopped stocking it when it got banned for construction...

May end up going the 3111 route just for simplicity of finding the material....

M.

[turkey]

you can get it, I know we had a build on the old forum just down the road from me in Surrey who used it. No idea where he got it from tho, although on reading heat and water seem to increase its degradation? These seem common elements for an oven outside in the UK, but I have no real clue on it tbh.

[spinal]

Yups - one of the reasons that HAC building were collapsing in the 70s was that heat and chemicals weaken concrete made with HAC.

That said, my understanding on homebrew fire mortar is that the cement is only structural until firing. It serves as a hydraulic binder until the temperature cures the clay, which then is what holds the mortal together. That's why portland works, even though it disintegrates at 600 or so.

By using HAC, I'm hoping that instead of having some more aggregate (essentially what portland will turn to under heat) in the mix, I'll have some conductive alumina

That's the theory at least!

M.

[spinal]

A minor update as I didn't get a chance to go buy the vermicrete...will probably end up there this weekend at some point...

Concrete slab now curing; more water is added 2-3 times a day (depending on where I'm working on the day )


It's been curing for 5 days now - plan is to cure at least 2 weeks before the bricks start going on top. So plenty of time to lay the vermicrete and order the vermiculite board and bricks!

M.

[spinal]

Right, finally got around to buying the vermiculite this morning. I got it from Jewsons, at just under £11 a bag inclusive of VAT. I bought 5 bags, but ended up using only 2.5 bags for the base (10cm deep).

Measuring the frame to pour the vermiculite into (yes, parts are indeed held together by duct tape!)


The contents are pulled out and the concrete is swept; ready for the vermiculite.


Vermiculite poured and levelled. I ended up using a mix of 25:5:7.5 in a bucket (25 jugs of vermiculite, 5 jugs or portland, 7.5 jugs of water). This uses 2.5 bags of vermiculite and 1.5 bags of portland.

Upon seeing this, my friends first comment was "wow - you're building a millenium falcon shaped oven!"

Now it's all covered again and ready to cure. At some point tomorrow I'll check if it's ready to be moistened with water again. Planning to cure this 2 weeks; of which one week it'll be kept soaked. The second week I'm thinking I wont water it so that it starts drying out.


M.

[spinal]

The frame has now come off, and the vermicrete spent the weekend in the sun drying without the plastic. Stupidly, I forgot to put the plastic back on last night, so I reckon today it may get wet again.

I'm thinking I may use the waste wood to create a little roof so it can dry without sweating in the bag and trapping moisture...



Also - started playing with grinding concrete. One of the edges had bulged a bit, and as I plan on covering it later with stones, I used it as a test piece for my coarse grinder. I like the result, so I may end up doing the work-surface out of terrazzo (polished concrete)... but may add some dye to get a different color, and more small rocks into the aggregate so that not so much cement shows. Basically, I think I'll need to do some playing... but there's time yet!
europoli.org/wp-content/uploads/2012/08/grinded-concrete-600x448.jpg [/img]

M.

[spinal]

Yesterday I got two pallets.

One with firebricks (a total of 211 firebricks - about £1+VAT each), a bag of fire clay (£15+VAT), 7-odd meters of 128kg/sq.m insulating blanket and 2x 40mm insulatingboards - this lot was from KilnLinings (£50 shipping).

The second pallet was from johnwinter's (johnwinter.co.uk); this containted 4 bags of fire clay (£15+VAT) and 5 bags of grog (£15+VAT). Shipping was £25.50 - and they gave me a free pair of furnace gloves. No idea what to do with them; but I reckon they'll look good while cooking pizza

I'm still waiting for a pallet of ciment fondu (HAC/CAC - £11+VAT per bag). That said, kerneos have been very kind and sent me a free drum via DHL. So I can get started with trial mixes!

Anyhow, this meant that today I could get some work done.

So - first stop was NifeIsLife to buy some flour as I was running low. Decided to stop buying 1kg bags from my local supermarket and go ahead an buy a bag of caputo blue from a local warehouse.


Once home, I donned a pair of disposable overall (I must admit, they make one look like a giant sperm) and cut the insulating board for the base.


Next I laid out the bricks for the heart in a pattern, and using a special tool to draw on bricks*, traced out the outline of the bricks that needed cutting.

* (on a separate and totally unrelated note - I need to buy swmbo a new mascara pencil - they write REALLY well on bricks )

At 18:00 I decided to let my nehibors rest a bit as I had been using the mitre saw and grinding disk for the last hour or two. Hence, this is where I stopped.


I put a very thin layer of fire clay under the bricks (a sprinkle - just enough to make a light dust. This helps me reposition the bricks).

As I was in a rush/impatient, I didn't soak the bricks. I've been cutting dry, so had a nice pile of grog in the vacuum (I connected the vacuum to the saw, so it collects some of the dust. I'll use this in the mortar/shroud later on.


Also, I have a range of offcuts. I'm planning to use some in the build... but any ideas on what else to do with these?


Tomorrow; I'm hoping to get the sailor/soldier bricks cut, placed and mortared in. Then as soon as I get the rest of the HAC I can do the dome!

M.