Vibrating Concrete and Vibrating Castable Refractory

I am building the 28" Mattone Cupola. The materials list and instructions call for 880 lbs of 5000PSI concrete. Well, I used a concrete vibrator to get the air bubbles out during the hearth slab pour, and it ended up taking another 100 lbs of mix (extremely little waste). I am assuming the vibrator was just really efficient at removing the bubbles. No big deal, except now I am worried that the same might happen for the oven (cupola) pour itself, where I won’t be able to just go buy some more castable refractory locally.
How much “excess” refractory is provided when you order from Brickwood?
Has anyone used a concrete vibrator and had a similar experience with a significant shortage of material?

John, I put out a help call to @BrickWood on this question. I sure understand your concern, and I want to be sure you get the best information on it.

When water is added to standard Concrete Mix - it can be a little airy… and a little soupy. A concrete vibrator removes the air and thickens the soup.

When you make / mix Castable Refractory with water, you are using a VERY LITTLE bit of ICE COLD WATER (the colder the better - it slows the curing process). You’re going to add just enough water to get the Castable Refractory to the texture of cookie dough… or pizza dough… or Playdoh.

If mixed correctly, a concrete vibrator could, would and should NOT be needed.

Recently, we changed the 28" Mattone Cupola from 13 bags of refractory to 14 bags of refractory. For some customers, 13 bags was cutting it too close. So we recommend purchasing 14 bags of Castable Refractory.

How to Properly Mix Castable Refractory with Stainless Steel Fibers - Construction Materials Needed to Build a BrickWood - BrickWood Ovens