Hello Jack,

One of the better material models for concrete plasticity is the microplane model, used in combination with the newer coupled-physics elements. These models have shown excellent correlation with experimental data.

There is a substantial learning curve to become familiar with using plasticity material models. There are many plasticity models to choose from. Most of them can be found in the Engineering Data library. Each material model has its own set of property values. Those values usually require some experimental data.

There is a Technical Note on concrete in the ANSYS Help system.  Here is a good discussion to read.