Thank you zoomer for your advice.
The main reason why we need separated components in the IFC is that this is a request from our client (Lead Architect).
For our current project, there are several types of paving elements and patterns. When we export Hardscape or Slab to IFC for coordination (in Solibri and Navisworks). All elements are white and solid. So this is hard for our client to see the design intention. Stone, Granite, Black, Gray, Brick, ... in IFC, all white.
We have to do some work around this week by converting all hardscape and slab to Mesh and then re-assign materials.