Emergency work is being carried out at Birmingham's Spaghetti Junction after it was discovered that sections need urgent repairs.
The slip-road onto the A38(M) Aston Expressway from Tyburn Road is closed because the Highways Agency needs to repair the crumbling concrete below.
Some parts of the M6 around junction six will also be closed overnight.
The Highways Agency said work carried out this weekend was not planned but ordered as a matter of urgency.
Andrew Hitch, of the Highways Agency, said: "During routine inspections our structural engineers advised that this section of motorway on the slip road was in need of repair.
"In addition to that we've put loads and loads of salt and grit on our network which actually goes into the joints and attacks some of our structures that we have to do further maintenance on."
The Highways Agency said it hoped all work would be finished in time for the Monday morning rush hour.