Our new $1.5 million new Mazak horizontal mill does not have grout, it sits on a concrete pad that is poured into the floor to stabilize it. Not many people use grouts our epoxy anymore because you have to jack hammer it out when your survivors take it out of your garage or basement after the estate sale.....
I think that Frank was referring to filling the base of the actual machine to provide more mass and to dampen vibration. Not for setting a base for mounting the machine to. This filling of the cast iron base is used on the smaller type Drill/Mills. I also understand that some manufactures have also used this practice.
I would suspect a $1.5 million machine would be heavy enough already. )
Cheers,
Rangikea