Hello, I am almost done making a round mini forge out of fire bricks and satanite.  The bricks are 2.5 inches thick and I have about 1/4'' of satanite lining it.  But satanite does not give much structure, it is not like mortar.  Could I use regular cement on the exterior of the bricks just to hold it together or will the heat travel that far and crack the cement or mortar.  Thanks

Satanite isn't for structure, it's why it's called a "refractory". It's job is to absorb and even out heat in a forge, giving you a more uniform temperature across the cavity if the forge is constructed right.

Cement on the outside of firebricks could possibly be ok, but the problem is cement holds moisture, and moisture + high heat = steam. Steam expands, and trapped steam can cause cracks, breaks, and potentially explode and send shrapnel into places you don't want sharp, high velocity chunks of cement flying into.

If you're looking to hold everything together, you can use angle iron and bolts, similar to this:

If everything is round, depending on the size, you can use hose clamps too.

You can hook worm drive hose clamps together to make a clamp as big as needed.

People sometimes ask me why I have my forge held loosely on it's cart.  I remind them about differing indexes of expansion do to temperature.  As my forge shell is old Oxy tank I'm sure it's stronger than my welds are; so I mounted it so it can stretch and relax without stressing them.

(Also it's a lot easier to mount and dismount when taking it n the road.)