Well, I can tell you what, you certaintly couldn't use concrete to make this following peice:
The ark.
I didn't do size listing because we only have best-guesses right now, but with it 'petaled' like that, it's approximately 10 times the size of halo, or 100,000km (100,000,000 meters) in diameter. Petaled, it's almost as big as Jupiter, and unfolded it's actually probably bigger.
So sorry, but if you wanted to make an Ark, you don't have the resources at all, heh.
(Note, that IS the same max file that I had before, but the scale is so rediculous that it was having z-depth rendering problems, so I went with an offline render. The pelican, PoA, T&R and Cov Capital ship are all still there, just invisible several times over.
And yes, I know the 2 'arms' on it bend a bit weird. I made this model in 5 minutes or so. Max doesn't support editing or moving stuff on that scale, so I had to work small, and then inflate it.)