Answer:
Generally, you can create and use your own materials. However, when entering data in the Material Library, it is important to ensure that the materials can also be used in the add-on modules: The specific weight has an impact on the design and on the formulas available there.
If you set the specific weight to 0 when creating a user-defined material, this material cannot be designed in the add-on module.
The specific weight of the material created should be adjusted in the Material Library; for example, for lightweight concrete only. If you do not want to consider the specific weight and thus the dead load as loads, you can set this to 0 in the "Edit Material" dialog box.
