FB refractory mortar as material for flue?

[Eric Pfeifer]

In finishing my build I bought and had shipped all the way from California 5 bags of FB mortar. It's too much hassle to find the right stuff in the right quantities locally. I am VERY pleased with the stuff, as it has great workability, flow characteristics, and is spot on the right color for firebricks!
Wish I had used it throughout the build. Here's my question:

Can I use the stuff to build my flue area, using the FB mortar as a castable refractory? I want to make a mold and pour the stuff, and then set my Duratech chimney adapter onto it. Should I use some chicken wire in the mold cavity as a sort of "steel reinforcement," or should I just use it pure? If this won't work, I'll need to buy some of the old fashioned gray stuff.

Thanks
Eric

[Dutchoven]

Re: FB refractory mortar as material for flue?

Surprised no one has answered Eric. Although I have not used the FB mortar...I would guess that it would be suitable if it were not too large a section. There are many refractory castables that are mentioned and just like most standard mortars are similar to concrete but not exactly the same I think the same might apply in the refractory mortars/castables...hopefully this might refresh the thread and perhaps get someone else to help also
Best
Dutch

[david s]

Re: FB refractory mortar as material for flue?

Castable refractory usually has aggregate, which is fired fire clay,or grog (pottery term) that is up to about 1 mm in size while the mortar uses a much finer aggregate. If you cut the mixture by adding a heavier aggregate you will weaken its strength. I suspect that the mortar will work ok. If it is for the flue area then the temp won't be so high so chicken wire would probably work ok, but the industry standard is stainless steel needles, but seeing it's probably only going to reach 300 C or so then the ss needles are probably an overkill. I think you would be ok to go with chicken wire and ref mortar, but I could be wrong. My wife reminds me frequently that I often am.

[Eric Pfeifer]

Re: FB refractory mortar as material for flue?

Thanks guys. I opted to cast the vent/flu with FB refractory with many many chunks of the firebricks left over form the saw when tapering the bricks for the dome. Will report on its behavior under heat soon.

[david s]

Re: FB refractory mortar as material for flue?

Pound the cut brick bits until there are no pieces bigger that 1/4"