The work, which begins on April 4, will involve the replacement of four miles of worn out steel barriers with a concrete system.
Narrow lanes and a temporary 50mph speed limit will be in operation in the area while the work is being carried out.
Highways Agency manager, Dave Sledge, said:
Concrete barriers reduce the risk of vehicles involved in accidents crossing from one side of the motorway to the other, with the additional disruption that causes, and improve safety for road users and road workers. They also last longer than traditional steel barriers.
The work has been carefully planned and where possible, will be lifted during busy Bank Holiday periods. We would remind all drivers to pay extra attention while driving through road works and observe all speed limits which are there for everyone’s safety.
The work, between St George’s railway bridge and Lox Yeo Culvert, is due for completion by 4 July. A temporary 50mph speed limit will be enforced for the safety of drivers and the workforce.
To allow the work to take place safely, there will also be narrow lanes in both directions and a series of slip road closures, which will take place overnight where possible, when there is least traffic.
During junction 21 northbound slip road closures traffic will be diverted to junction 20 to turn around and for southbound slip road closures, traffic will be diverted to junction 22. No slip road closures or traffic management measures will take place over the Easter bank holidays.
Members of the public should contact the Highways Agency Information Line on 0300 123 5000
Journalists should contact the Highways Agency press office on 0844 693 1448 and use the menu to speak to the most appropriate press officer