A property that is related to porosity and that very much depends on particle sizing and packing is the permeability of the castable.
In ASTM C71, permeability is defined as “the capacity of a refractory
for transmitting a fluid or gas” (18).
This property is important since the ability to safely dehydrate or bake out a refractory castable depends on its permeability.
Permeability can also play a role in gaseous corrosion reactions.
Permeability is measured per ASTM test method C577.