Here is a screen shot of an welded structural steel frame for a vertical mill, using compressed concrete or a granular aggregate for compressive loads and vibration. Read a paper on curing concrete under pressure and came up with this to give welded steel the properties of cast iron. Compressing the concrete mix displaces excess water and air for higher compressive loads. As modeled this comes in at 4200 lbs. with out concrete, maybe a hollow steel tube would be a better choice?