You can use the Settings/Structural Materials command to change the concrete and steel types of the concrete objects in your project on an object basis.
Process steps :
Click on the Structural Materials icon from the Settings menu.
You will be able to see the list of concrete elements in the opened program.
After selecting the element for which you want to change the concrete or steel types, select the appropriate concrete, steel type and stirrup type from the drop-down list and close the dialog by clicking the OK button.