How much crack is too much crack?

[aikitarik]

#78

(M) Tarik, did you mortar the re-bar to the inside, or outside of your clay liners? __________

Rebar? Good idea. I guess I could mortar some rebar to the outside. I've only got two pieces on so far until I finish my roof.

(M) I have a thought for a temporary chimney roof. Consider cutting the 5th liner (if you have an extra) on the diagonal with your angle grinder masonry blade. That should produce 2 ninety degree tile roofs that you may be able to balance over the opening until you decide on something more decorative. If you leave some of the adjacent corner edges you'd have one roof too small but the larger one would look more finished. You only have one chimney.

Interesting idea. I'll ponder it. In the meantime, checkout http://www.designtoscano.com for dragons!

[aikitarik]

Marcel,

I have only 2 segments of chimney flue stacked in place currently, with refactory mortar holding them together and no reinforcement or bracing. It is my intention to build a cage around them out of the steel studs and somehow connect the chimney flue to the cage.

The idea of mortaring in rebar as reinforcement, especially here near the epicenter of the 1989 Loma Prieta is entirely logical and I'll probably do something of that sort, perhaps drilling a few holes to drop the rebar into. I wouldn't place rebar on the inside of the flue pieces simply because of the caustic (and moist) nature of the smoke and offgased chemicals from burning wood which would lead to rapid rusting.

Sorry if I was unclear earlier.

[janprimus]

Rusty rebar? Nay!

I wouldn't place rebar on the inside of the flue pieces simply because of the caustic (and moist) nature of the smoke and offgased chemicals from burning wood which would lead to rapid rusting.

IMHO
Actually, the creosote from the smoke would envelop and I would wager somewhat preserve the rebar located within the flue. It gets quite a sticky almost waxy buildup on it.
Chad

[aikitarik]

IMHO
Actually, the creosote from the smoke would envelop and I would wager somewhat preserve the rebar located within the flue. It gets quite a sticky almost waxy buildup on it.
Chad

So you would recommend rebar mortared along the inside of the chimney flue?

[janprimus]

rebar in flue

I dont know that I recommend it or not, I was just saying I didnt think it would rust. Did you ever see a rusty piece of smoked salmon? ;-P
My main concern is the differing rates of expansion and contraction of the flue tiles vs the rebar. I think this is why they cannot put reinforcing metal in refractory cement because of the differing rates of expansion which would certainly cause the material to crack. Perhaps if it were epoxied somehow or epoxy in the mortar... I just dont know how it would stick. The more I think of it the less it sounds like a great scheme.

[aikitarik]

I dont know that I recommend it or not, I was just saying I didnt think it would rust. Did you ever see a rusty piece of smoked salmon? ;-P

Well, no, but I've seen plenty of rusty metal flues and dampners. I think I'll stick with my original plan of placing structural steel framing outside the chimney and finding a way to tie them together (mortar or screws).

[Marcel]

I'm a little rusty at this sort of thing, but, ...

(#82)

(M) I wouldn't worry about rust as the re-bar will be covered with mortar on the inside of the flue liners. I don't think civil engineers worry about rusting re-bar inside their prestressed concrete re-bar reinforced slabs, nor the iron I beams in skyscrapers.

(M) I also don't worry about differences in thermal expansion. We all have rebar in our refractory hearth layer. Also, the temperatures in the flue liners will probably be way below that of the dome.

(M) Having said the above, I think it is probably fine to use the re-bar on the outside but in my case, because my liners are sitting only on 2 pieces of flat iron, I don't want to add unnecessary weight by cladding my liners, so mine will be mounted inside imbedded in a bead of mortar in each corner.

Ciao,

Marcel