For perspective on the potential material used for this rendering, here is a rendering for the Homewood Suites built recently in Philedelphia:
image source: Univercity City, Philedelphia Penn http://explow.com/University_City,_P...,_Pennsylvania
The completed Homewood Suites in Philly looks like this:
image source: nakedphilly.com
Looks like concrete preform with coloured metal cladding. That's not to say this will be the same material used here, just saying that was what was used there.