Erik Kostson
Ansys Employee

Concrete modelling can be difficult to get convergence - one way we have is to use the material solution parameter (MSOL) for the Menetrey-Willam.

See slide 10 in the demo I have made for modelling concrete using the Menetrey-Willam model.
Also this link shows and explains how to use this :
4.10. Geomechanics (

Of course it is not possible to always get convergence with this and one can not guarantee that it will always converge, but it will at least aid convergence and be probably a better option then the default option, especially when we are at total failure of the structure and beyond (post failure response, e.g., softening).
All the best