The Material instance parameters of elements in your model are included in the export process of your model to analysis and design applications. Revit provides default concrete, steel, wood and generic material properties. You can use the default material definitions as the basis for adding new physical material types to your model database. For example, you can create a concrete sub-type called Concrete 4000 psi and adjust the physical parameters accordingly for your project.
You add new types and edit these types by using the Structural Material Properties dialog.