Castable throat chamber

[MikeD55]

I’m looking to cast a one piece throat for the transition from the inner and outer arch to the flue pipe. Any advice or tips. I’ve looked at some castable refractories like KS4V plus but it seems pretty dense. I’d like to go with something a bit lighter plus still strong and can handle direct flame contact. Was thinking of basalt fibers instead of stainless steel fibers to take further out some weight.
Thanks

[david s]

Using a light weight castable results in a loss of strength as well as making the casting far more vulnerable to damage from tools and larger bits of wood. The entry needs a dense castable IMO. Reinforcing fibres will increase the strength a bit, but nowhere near enough to make an insulating castable sufficiently strong enough to withstand the bumps and abrasions experienced in the entry. You can increase strength by just making it thicker. I use a very thin cast section around 25mm with dense castable reinforced with stainless needles and AR glass fibres. I’ve had no trouble with failures.
i do also have basalt fibres, but find them (at least the ones I have), more difficult to work with because they tend to clump easily ss needles and AR glass fibres disperse far more readily.

[MikeD55]

Ok thank you. I’m basing mine off the design from the firebrick company but significantly taller. I was shocked how thick there’s is at 6cm