ACI states the following:
For the integrity of the structure, it is important that all construction joints
be defined in the issued for construction drawings and constructed as required.
Any deviations should be approved by the engineer or architect.Immediately
before new concrete is placed, all construction joints shall be wetted and
standing water removed.
Construction joints in floors shall be located within the middle third of spans
of slabs, beams, and girders. Some engineers say in the mid-span where the shear
value is minor as possible (this makes sense).
Construction joints in girders shall be offset a minimum distance of two times
the width of intersecting beams.
Beams, girders, or slabs supported by columns or walls shall not be cast or
erected until concrete in the vertical support members is no longer plastic.