I am just wondering... why does it need to be in so many pieces? The
more sections you pour (especially the smaller ones you describe) the
more cold joints you will have, the more movement you will have, and
the harder your floor will be to finish.

You shop floor should be burned smooth with a troweling machine so that
you can easily sweep away all the dust and debris you will generate.
With all those cold joints, your floor will be rough, your machines
will not roll, when the floor heaves due to climatic conditions your
floor will be uneven and if all sections are not properly doweled to
together, they will separate with wild abandon.

This is you shop; take the money you are spending on the mixer and
concrete, and pour it in one piece if you can. Your expansion joints
should be cut into the new floor with a walk behind concrete saw
(easily rented) about an inch deep to divide it into sections that will
move with the substrate.

When I was pouring tilt panels and lots of concrete all the time, we
cut our panels with the walk behind saw the day after pouring so the
concrete was still really green and easy to cut.

Robert