The crane on the lorry is believed to have elevated, striking the footbridge and causing sections to fall on the the busy road.
The lorry driver, a man in his early 40s, was taken to Doncaster Royal Infirmary where he was treated for minor injuries, South Yorkshire Police.
The police have impounded the lorry for further investigation.
A spokesman for Plasmor said: “We don’t know how the crane came to be elevated. It’s a freak accident.”
No one else was hurt in the incident.