Lanes could remain closed between junctions 6 and 5 until the weekend while repairs to the concrete barrier are completed.
Two motorists were lucky to escape unscathed after a crash on the M25 on Monday morning, in which a van and lorry were in collision before the latter vehicle jackknifed and then smashed through the central reservation.
The motorway was closed clockwise between junction 6 (Godstone) and junction 5 (Sevenoaks in Kent), while three lanes of the anticlockwise carriageway were also shut.
Emergency services were called to the incident near Clacket Lane Services just before 10am.
Surrey Police, Kent Police, the Highways Agency (HA) and South East Coast Ambulance Service (SECamb) attended the scene.
A SECAmb spokesman confirmed two people had been checked at the scene and one was treated for shock, but neither required hospital treatment.
As of 4pm on Monday, two lanes remained closed in both directions.
The HA said the accident left a nine-metre gap in the central reservation, and that the repaired concrete might not have "reached its full strength" until the weekend.
An HA statement said: "The Highways Agency is working hard with its contractors and the emergency services to reopen the lanes as soon as it is safe to do so.
"A temporary barrier is being installed on the anti-clockwise carriageway and once in place one lane will reopen to provide three lanes open to traffic.
"Two lanes remain closed on the clockwise carriageway while the surface condition is assessed following a spillage.
"Permanent repairs to the barrier will be carried out overnight.
"The outside lane will remain closed in both directions until the concrete has reached its full strength, which is estimated could [at] the weekend."
Long delays built up following the accident, with six-mile tailbacks clockwise and for five miles anti-clockwise.
There were also knock-on problems for the M26 in Kent, which was closed to relieve pressure on the M25, and on the A25 in Oxted and Sevenoaks as drivers tried to avoid the motorway.
Police advised motorists to find alternative routes, while the HA also warned of "long delays" due to the ongoing recovery work and clean-up operation.
A Kent Police spokesman told Get Surrey: "There are no injuries reported.
"Work on the central reservation is going to take several hours, with delays in both directions."