Batman arkham knight: game stuck at stop Scarecrow from blowing up ACE Chemicals
Solution 1:
Posting my comment as an answer so other people with this issue can also have an idea what to do:
There should be a 5th worker somewhere that you missed: 1 dead in the hut where you open the gate, 1 on a side building across the pipes (where the Knight does his monologue), 1 right after the gas pipe, 1 right before the elevator and 1 after the elevator. If you did get all 5 workers, then this is a bug and you might have to restore a save game backup.