Concrete Floors that are liquid when they are poured are actually drying out
(usually as slowly as possible) as they are cured -- as are masonry walls.
 It is preferable not to move collections into the building until it has
stabilized -- something that may take many months and the space can be
monitored for humidity.  Also, concrete usually contains some combination of
added chemicals called admixtures that expedite the construction process or
improve the material's properties in some fashion.  You should learn from
the contractor, engineer or architect of the temporary storage building what
was used (get the brand name, quantity per cubic foot, and chemical content
of any admixtures) and then seek advice from a conservator about whether
there are harmful ingredients that may be offgassing during the curing
period -- also, for recommendations on sealers that are not harmful.  The
American Concrete Institute headquartered in Detroit is the industry's
research and standards group and they may also be able to help you.

It is standard construction practice to place a vapor barrier under a
concrete slab on grade but check that this was done.  Also, very thin 4 mil
polyethylene sheets are often used and these may be easily punctured during
the process -- by the gravel course below or during the placement of steel
reinforcement bars or mesh and formwork.  I would not place anything
directly on the floor -- also in the event the space can flood through
natural disaster or from plumbing or roof failures in the building.  You may
also want to avoid placing items against the wall if its construction and
interior and exterior T & H  differentials suggest there may be condensation
or vapor migration.