Erik Kostson
Ansys Employee
Just a side note, that might be of help, when you study RC structure.
Having worked with some concrete, I would not trust the FE results after the failure load, and in the post cracking region.
Upto failure it (concrete model in solid65) might be OK, but needs of course to be validated/verified, but after that (failure load) it is hard to trust the results. That is fine for most times when designing, since we care often about the failure load and not the post cracking response.

Also for your reference that factor (tensile crack factor) is just there typically to aid convergence, and not really to account for post crack behaviour. This is noted in the help manual under keyopt 7 for solid65:

Include tensile stress relaxation after cracking to help convergence

All the best