The bridge was supposed to be closed overnight from 2 a.m. to 7 a.m., but the reopening has been delayed because of the time it has taken workers to cut a median on the bridge so that cranes could place the 'superbeam' more easily.
The beam that is being installed this morning is meant to reinforce a cracked girder.
The crack was first discovered three weeks ago and has since doubled in length.
When the bridge does reopen, a lane in either direction will be what commuters have to contend with until Monday at 5 a.m.
At that point, traffic is expected to return to normal.
The new Champlain Bridge is projected to be completed by 2021.