Heat resistant mortar - hydraulic or ceramic drying??

[aureole]

Re: Heat resistant mortar - hydraulic or ceramic drying??

Hehe, yep definately still female the last time I looked...

Ooops. Sorry about that

It's a funny thing... I've got two options: the fireclay mortar or the superplastic. My current plan is to butter the bricks finely with the superplastic, then use very fine castable concrete mix in the wedges (provided it's workable enough to do that). I'm going to have a play with the materials to check it'll bond well enough and fill the voids.

Anyone have a clue about plasticising compounds at high heats? Is it okay to add them and/or PVA to a high-heat mortar?

[Frances]

Re: Heat resistant mortar - hydraulic or ceramic drying??

Hehe, yep definately still female the last time I looked...

Sorry I didn't answer earlier, but we were away for a couple of weeks. Sounds like the mortar I used wasn't the same as what you're talking about at all. Mine was a dry sandlike powder which needed to be mixed with water before use.

Here's another thread where I go on about it at length , and so far it seems to be working just fine! (further long term testing is being undertaken as we speak)

http://www.fornobravo.com/forum/f8/heat-dry-mortar-made-refactory-clay-2783.html

Oh yes, dvonk has since built an oven with the same sort of product.

[asudavew]

Re: Heat resistant mortar - hydraulic or ceramic drying??

Frances finished his build a while ago !

Yeah SHE finished a long time ago!

[atdabch]

Re: Heat resistant mortar - hydraulic or ceramic drying??

be carefull of the pre-mixed mortars...the ones i found are not water-proof when dry...constant rain and wetness will break them down

[aureole]

Re: Heat resistant mortar - hydraulic or ceramic drying??

Ah,

I've got an option b given to me, I've been recommended/suggested: air-drying mortar on the inside of the bricks, followed by some very fine refractory concrete on the outside. The concrete I'm getting has a very fine ballast/aggregrate inside. If this is a stupid idea, I've got the backup plan of 75kg of fireclay on the way. Not sure what I'll do with all the spare refractory stuff!

Quite an interesting conversation with the guy from Midlands refractories: he essentially told me I was completely mad to try this (although he conceded the Romans definitely knew what they were doing, and if ovens survived the volcano at Pompeii, they must've got something right!). He suggested the air-drying stuff is used (very, very thin) because you don't want any joints between refractory bricks.

Interesting stuff, I'm hoping the refractory concrete/cement I get is pretty close to refmix (I'll check the label when it arrives).

[dmun]

Re: Heat resistant mortar - hydraulic or ceramic drying??

Frances used fireclay-and-sand only mortar (no lime or portland), on the advice of local masons, and it seemed to work out fine.

[aureole]

Re: Heat resistant mortar - hydraulic or ceramic drying??

Yeah: I'm all ready to go. Hopefully going to order the bits today, and get them soon so I can go make the dome as soon as the english weather sorts itself out!

From my scraping of the forums, I think it's the case that Hendo and Frances have definitely used the heat-drying wet stuff. I think other UK builders have used a fireclay and lime mortar. I'm going to get 60 kilos of fireclay and 100 of air drying wet-mix mortar and have every angle covered!

[Breven]

Re: Heat resistant mortar - hydraulic or ceramic drying??

Well, I guess the heat cured mortar works.
Are your pics current? Looks like you're about ready to start the floor and dome eh?

[aureole]

Re: Heat resistant mortar - hydraulic or ceramic drying??

Sorry, it was me resurrecting an old post: Frances finished his build a while ago (and hasn't AFAIK, fallen down!) - mine is still very much an ongoing project!

[Breven]

Re: Heat resistant mortar - hydraulic or ceramic drying??

Frances-
Can't help with with your motar question. I mixed my own using fine sand, portland cement, and fireclay. Seems to be workign great. As far as your question about your dome colapsing if it rains- I don't think so, as long as you do a full course and don't leave the course half complete. The laws of gravity and the 2,000 year old arch design (which is the basis of a dome shape) won't allow the bricks to colapes as long as they are wedged together in a circle tightly. Unless your mortar completley breaks down in water.

[aureole]

Re: Heat resistant mortar - hydraulic or ceramic drying??

I've got a very similar question myself: how did you get on with the air-drying mortar?

According to the link below and some other stuff I've read, "hydralic" means the more tradition portland cement-like action: it needs water to set.

Build Masonry Fireboxes

I've been offer the stuff that comes wet in a tub and dries out - but this, apparently, isn't good for exterior builds or big gaps.

[Frances]

Re: Heat resistant mortar - hydraulic or ceramic drying??

Hello? Anybody?

I've been reading past threads on similar subjects, but didn't find any that give tips on working with heat dry mortar. Cement based mortar I'm used to, but this is a bit different. Isn't it?

I mean obviously I'm going ahead with building the dome, but it would be nice to know what I have to watch out for sooner rather than later.

Frances

[Frances]

Re: Heat resistant mortar - hydraulic or ceramic drying??

One last thought: if rain gets on my half finished dome, will it collapse? I have this horrible picture in my head of the tarp blowing off and all the mortar melting away in the night...

[Frances]

Re: Heat resistant mortar - hydraulic or ceramic drying??

I have FINALLY (Hooray!!) stared work on my dome today - pictures will follow. The mortar is reall good to work with. It must have lime in it, because its really sticky stuff.

I have two more questions though:
As its heat-dry mortar, am I right in thinking that it doesn't have to be kept wet? Should I cover it if the sun is shining on it?
And seeing as it doesn't form a chemical reaction with the water, would it be ok to wash my tools in water afterwards? Rubbing them down with newspaper sure doesn't work...

Thanks for all your help.
Frances

[maver]

Re: Heat resistant mortar - hydraulic or ceramic drying??

Frances, a few thoughts on workability and holding. If you have mason's lime available, it really helps to make the mortar plastic and sticky. It is supposed to hold up with thermal cycling better than portland cement as well. The tradeoff is it does not harden as much as portland and not as quickly (but for those upper dome bricks stickiness may be more important than a quick bond). If you don't have to modify your mortar for stickiness or workability then don't - I'm sure mortar you have will have better performance as is than as modified.