If the rock is already crushed you can skip a few steps in the smelting process.
In addition, the total mass of the asteroid belt is something like 4% of the moon's (and half of that mass is in the 4 largest asteroids). You would be better off just mining the moon.
These might be transported back to earth. Plus there's iron, cobalt, manganese, molybdenum, nickel, aluminium, and titanium for construction of moon settlements and factories.