Italian to English Tech/Engineering Construction / Civil Engineering construction

This is describing a factory which produces panels that are basically building units for quickly assembling houses and warehouses. The factory has an annexed concrete production plant which also produces "intonaco portante e di sostegno". Now, I assume in this case "intonaco" is plaster and "portante" is "load-bearing plaster"- but isn't "di sostegno" similar? What is the technical terminology to distinguish the two types of plaster produced in the factory? Thanks :)