As you should know. After the Civil 3D 2018 version, the FBX export was removed.
However, we must still import 3D objects from Civil 3D with texture to InfraWorks.
I solved it by using.DAE, step by step.
- Import Civil 3D object to Sketchup;
- Export it to.DAE file;
- Import.DAE file to InfraWorks.
I saw it worked well. It keeps material, texture, and geometries from Civil 3D objects.
Let's try and receive your results.
I feel satisfied with this approach.