This is just my opinion and since it is free take it for what its worth
From your comments regarding the entire construction process, I think that
you should not attempt to build this structure by yourself. Before you begin
you need to educate yourself in basic construction at a level much greater
than this news group can provide. Even then the book knowledge is not the
same as being able to apply it in a practical sense. Reading a chapter on
floating the finish of the concrete is very different from doing it. But the
book knowledge will allow you to converse with contractors.
While you may not have to deal with a building inspector or comply with
"city" codes in your location you should not take that as the OK to just do
it how ever you want to. In general building codes and inspections are not
necessarily bad, they make sure the structure is safe and built to a minimum
specification. The questions you have asked indicate that you do not have
any experience in basic structural construction, if there is a construction
site in in your area, particularly if it is a new home being built you
should check it out and really look at the way it is being put together from
the ground up. While I am not familiar with the type of foundations that
are typically used in your area, if you can observe the construction steps
of a concrete slab foundation you will see the footer and probably beams
being dug into the soil, the beams will most likely have static tension
cables in addition to the rebar. I am not saying that tension cables are
necessary but you will need to do the soil / site preparation appropriate
for your area, a compacted sand base will probably need to be installed even
if excavation of beams is not required. A vapor barrier under the concrete
would be essential. Regardless of the exact construction techniques that
are appropriate for your soil conditions in my opinion rebar is cheap when
you are building a foundation, use extra, it will be money well spent.
Some utilities installed before the foundation is poured will be appreciated
for years down the road, well placed floor plugs can be very handy, even if
you do not plan to install electricity in the floor initially if you install
conduit you can pull wire later.
Some running water inside the shop would also be a great feature. Then
there is the general electrical wiring and breaker box, do you know how to
install the electrical service ? You will need to calculate loads and make
sure the appropriate sized wiring is correctly installed.
Concrete is not especially hard to work with if you know what you are doing,
if you don't you will wind up with one big concrete mess. Breaking up
concrete and hauling it off is not any fun under any circumstances. If you
do not know how to work with a normal mix product I do not think you will
stand any chance of success with some of high strength specialty mixes that
have been mentioned in this thread.
Electrical wiring is not especially hard either but there is a right way to
do it, and it needs to be done correctly.
If you are actually going to build a shop you should at least be pleased
with it when it is finished. Just from the posts you have made in this
thread I think you need the help of professionals.
Just my 2 cents worth, hopefully you will think about some of the concerns I
have pitched out there.