Police said a section of Highway 40 was closed in the city's west-end after a passing vehicle was struck by an object.
Several other vehicles also sustained damage, including punctured tires, after they drove over fragments on the road, said provincial police spokesman Gino Pare.
No injuries were reported.
A spokeswoman for the provincial Transport Department said the warmer weather may have been a contributing factor.
It wasn't clear whether the concrete fell from an overpass that was last inspected in 2012.
The state of Quebec's crumbling road infrastructure has been of particular public concern since a highway overpass in Laval collapsed in September 2006, killing five people.