Modular chimney section help!

[RichC]

Guys, just put my modular chimney section in today. It's 3 pieces + flue. I mortared the 3 sections together and the flue in place using refractory mortar. I didn't mortar the chimney assembly to the oven in any way which I think us correct?
This complete dome and chimney section is robe covered in fibre blanket and then vermicrete. There are some large gaps between the chimney assembly and the oven, how should I fill these or do they matter at all?
See pics below





Thanks

R

[david s]

Re: Modular chimney section help!

If it were mine I'd be filling them with 6:1 vermicrete, to reduce heat loss from the dome to the heavy entry castings.If you have any refractory mortar left then use that in preference to Portland cement for the mixture.

[RichC]

Re: Modular chimney section help!

Thanks David but would the vermicrete not crumble and fall into the doorway? The 6:1 that I put below the base us 'very' crumbly now. Could probably drive a finger right into it. I can sweep my hand across the top and gather a handful of vermicrete from it

[texman]

Re: Modular chimney section help!

Do have any firebrick pieces or casting you could use to cut and mortar into place to fill the gap? I would definitely fill/ cover it.

Texman

[RichC]

Re: Modular chimney section help!

I do Texman, I have 2 firebricks and a few slips about 25mm. That would mean mortaring the chimney arch to the dome though? Is th?t a good idea?

[texman]

Re: Modular chimney section help!

I think it is fine. They look like two different materials, so not ideal situation.
Will probably crack there but should be manageable. Dave's idea of vcrete with refrac will work too and allow for the different thermal factors. You can slather a layer of straight refrac on top of vcrete to keep it from crumbling there.

Texman

[david s]

Re: Modular chimney section help!

Use some crumpled alfoil or tissues to block up underneath until the vermicrete has set. Using vermiculite or perlite in the mix will reduce strength but will be more insulating.if your 6:1 vermicrete mix is really crumbly after it has set you may not have added the correct amount of water, either too much or too little and it does not work properly. It should be 3 parts water to 10 parts vermiculite or perlite approx.

[RichC]

Re: Modular chimney section help!

Thanks guys, I'm thinking I may wet some fibre blanket in cement and water and stuff it in, then cover over with vermicrete? The fibre blanket should solidify and also prevent any vermicrete that crumbles from falling in over the archway. Does that make sense?

Thanks

R

[david s]

Re: Modular chimney section help!

Thanks guys, I'm thinking I may wet some fibre blanket in cement and water and stuff it in, then cover over with vermicrete? The fibre blanket should solidify and also prevent any vermicrete that crumbles from falling in over the archway. Does that make sense?

Thanks

R

Sounds like a reasonable plan. Try it and report back.