This takes some understanding.
So the ring road (which runs from the north, near the A28 Peage exit and Auchan) is being dug up a mile or two north of Arnage, at between 7 and 8 o'clock on the ring.
Alternatives are to head for Angers on the A11 Peage (outer by-pass), and cut back on the D326, pulling off at the airport. The D92 might work, if you can get there, or come off the A28 south of Le Mans, just south of Ecommoy, and head north to Mulsanne.
I might try the ring road clockwise, and turn off at Carrefour and pray that the satnav will get me that far
If any of this is wrong, please let me know