[BroadHopper]

Bit surprise to hear that they use concrete. Concrete is porous and loses weight when it is dry and can absorb moisture and gain weight. Are you sure they use concrete? In the maritime industry, one would pump or drain seawater from ballasts to maintain a certain level on a ship. The Mt would surely be a lot higher in the water caring no passengers versus a full load of passenger and crew if they can't change the weight of the ballast.

Also concrete being porous will rust out the steel hull. Unless the concrete is in a seperate container, but that will cause shifting in rough water.

If the Mt is flat bottom like a barge, then then changing ballast will be less significent problem than a boat with a round or V hull.