questions on re-pointing 40 year old fire brick

[Marinecraft]

Hello and thanks for tolerating my ignorance. If this project did not risk burning by house down in a Rumford-style firebox, I would just use my physics knowledge and give it a roll.

ISSUE:
40 year old Rumford box needs some repointing, no less than 1/2 inch (UTLTIMATE MAXIMUM) and I have already removed weak or failed mortar with a wire wheel on an speed drill/

SEEKING:
Best recommendations on re-pointing mortar Mix. Purchased a product from "Rutland" but it only certifies to 2000 F where I know the fire bricks in my box can get a lot hotter than that (White Hot) on a cool night which I think is hotter than 2000 F.\\

ADVICE: DIY MORTAR in 1/8 layers or use the Rutland? Please I need expertise./formulae?

Thank you sincerely.

Marinecraft

new member

[ATK406]

Re: questions on re-pointing 40 year old fire brick

I don't know much about Rumsford Ovens (as far as I know their distinguishing feature is a geometry which reflects more heat out into the room), but I would be very suprised if your oven was getting as hot as 2000F. Unless you are using a blower on it or burning something other than firewood, I suspect your peak temperatures would not exceed 1500F and the Rutland product you bought should be fine. Do you have a friend with a fireplace and a themometer that you can measure the temperature of the firebrick wall?

Regards,
AT

PS: You might be more concerned about the chimney - as that is where most of your heat is going anyway. If the lower portion of your firebox is in need of repair I wouldn't assume that the chimney was any better.

[stonecutter]

Re: questions on re-pointing 40 year old fire brick

Your 40 yr old fire box was probably built with mortar or a portland/fire clay mortar. You should remove as much failed material as possible to a minimum depth of 1" before you repoint it.


Normally you don't want to have any joints more than 1/8-1/4 wide when using refractory mixes. The temp rating is fine on the Rutland mortar ( they make good product) and it should be suitable for what you are doing. A portland/fireclay mix will be ok too.