Castable refractory cement mix

[fxpose]

I'm about to cast my vent and have 25 lbs of this dry mix which can yield 2 sq/ft at 1 1/4" of cement.
My question is, can I add some crushed firebrick to this mix to increase volume? I understand I'm altering the mix ratio by doing this and thus may weaken the cast.
My reason for doing this is because I may not have enough cement to fill the mold....it's close by my estimation.

George

[wlively]

Re: Castable refractory cement mix

You can do anything, once.

I would think it depends on how much you are going to add and how challenging a shape your vent casting will be and the limitations of the refractory. This is a critical piece, so best to call the manufacturer or order some more.

I ran into the similar problem with mine, as I was casting the dome plug and the vent transition and wasn't sure there was enough KS-4. I ended up tapering 4 sides of a full brick and sitting that in the middle of the dome plug. I figured if the bond let go the taper would hold the brick. So, far it is still bonded very well, brick and plug are solid.

[fxpose]

Re: Castable refractory cement mix

Thanks Wade. The vent shape is very a simple rectangular box with a slight curvature at the front face.
I think I will take some firebrick remnants and crush them down to tiny pieces and add them accordingly to the mix.

George