I hope you are talking about the concreting activity.
Due to any reason, casting might stop.
say - concrete supply issue, machinery breakdown etc.
In those cases, the concrete should be finished by making it in line like a how concrete ends near stopper.
The remaining concrete structure should be casted within 24 hours to avoid cold joints in it.
If the delay is more than this, Bonding agents such as SBR or roughening of concrete surface and applying cement slurry on it at the time of concreting should be done.
There is as such no issue if the concrete gets halt due to any reason and if its finished, compacted well.
The concrete gains strength over period with good curing.
Till the structure get strength, we do not allow de-shuttering.
What can happen if such situation comes;
If concrete not ended in a line and allowed to flow over surface - it forms a layer of concrete which may or may not bind with upper layer and also at the thin ends, it will start de-bonding and peeling off.
Technically there is no issue, if the ending of halted concrete done correctly.
Example - i do cast columns, then slabs and beams and then again next floor column.
columns and walls comes in multiple lift (in some projects), also we cast slabs in parts for ease of work.
Stopper locations are just to ensure, in case you de-shutter the slab completely including the end portion where stopper is, there should not be a failure.
Hope you understood the concept.
In such cases, ensure proper compaction and construction joint preparation correctly.
What such thing can cause-
A leakage at joint, if not treated properly. From this leakage location, reinforcement steel will start rusting and the life or structure will reduce.
