The easies and quick way to modify properties of an object is using a simple python script component.
If you open a .struxml file format, the following code will look familiar as the material object follow what you see in the .struxml.
import System.Guid
import copy
newConcrete = copy.deepcopy(x)
newConcrete.Concrete.Mass = mass
newConcrete.Guid = System.Guid("{53635D15-5696-47F2-9084-B63C7A00F970}")
concreteMaterial.gh (52.5 KB)