Choosing Concrete from the Material menu puts you into "Concrete Mode". This means that all members modeled after entering Concrete Mode will be modeled as Concrete until the material is changed. Member and material properties for the concrete members are input through the PropTable and Layout menus.

To make changes to the properties of a Concrete member, you must first be in Concrete Mode.

You will notice that choosing Concrete from the Material menu has an effect on the Layout menu; specifically, a Layout - Walls command is added. Several of the commands under the layout menu are material dependent.