Cast concrete chimney vent

[Nev Grady]

I'm getting towards the end of my build and having had enough of cutting firebricks I've decided to make a cast concrete vent for the chimney connecting plate which will be the male part of the connection.

This will of course get very hot, so can anyone please tell me what's the best recipe to use for the concrete?

[dmun]

Re: Cast concrete chimney vent

This will of course get very hot, so can anyone please tell me what's the best recipe to use for the concrete?

You want to use a castable refractory product for this use, reinforced with stainless steel needles. Regular concrete will spall and crack, and shouldn't be used unless you line it with refractory flue liner, and provide an expansion space between the concrete and the outer chimney.

Once you get a quote on refractory concrete, you may think twice about cutting more bricks.

[wlively]

Re: Cast concrete chimney vent

Do a search on KS-4, the castable refractory I used to see comments.

It was not very expensive and for a vent transition you will need only 1, 55lb bag/bucket. I bought it here;Empire Refractory Specialists Shopping Cart

[Neil2]

Re: Cast concrete chimney vent

Portland cement based concrete is susceptible to heat. It will start giving up its strength if it reaches about 650 degrees.

Successive heating cycles will cause it to deteriorate.

[mikes334]

Re: Cast concrete chimney vent

I would put a liner in the chimney to reduce the heat deterioration.

[fxpose]

Re: Cast concrete chimney vent

Due to the unique shape of my vent I'm thinking of casting my vent as well.
I could also use the castable for the shallow landing as well, where it meets the oven floor.

George

[eprante]

Re: Cast concrete chimney vent

George,
check out the link by lcripe just below your post. He did an excellent job of casting a chimney vent transition.
Eric