Using Concrete to build space ships...

>
> How would the construction crew move on an asteroid?
> Wouldnt they use ion thrusters also to move forward or having to
> put pressure onto the ground?

The benefit of a stationary mining/refining process is that you can
use electrical power. This can be generated from solar cells/turbine
or if you have a nuclear ship, directly from the reactor.

You construct conveyors on the asteroid to move the material.

You mine the ice to develop rocket fuels to power the equipment that
moves material in the space surrounding the asteroid.

The asteroid can be the source of fuel, as well as the source of
solar cells. It is the source of most of the material that you need.

TangoMan