• Assuming that you want to source as much construction material as possible on-site (In-Situ Resource Utilization), simple materials like Polyethylene might be advantageous to more complex materials like carbon nanofiber etc
• Polyethylene can be processed at temperatures around 200°C, while steel would have to be heated to 1500°C. Especially in the early days, plastics are clearly cheaper than steel. Let's see whether we can get away with it:

A room-sized dome (i.e. sphere, but only the upper half, with sphere-radius r = 10 m, so maximum diameter d = 20 m if you cut at half height) with inside pressure p = 0.2 bar would require a thickness d = 6.66 cm roughly, if it's made of PE. That does not sound undoable! In fact, that sounds entirely reasonable and doable.

There's a third, less well-done page:

This is an RFC (Request For Comments). Leave your comments down below!