Look in http://www.the-construct.net/
More specifically: http://xfer1.the-construct.net/tribes2/mods/Archive/
However Quantium is pretty old by today's standards, I think the servers are running a newer construction mod now-a-days.
If anyone is curious as to what game the OP is talking about, you can download it at the link below for free, then you have to download TribesNext:
http://xfer1.the-construct.net/tribes2/ : tribes2gsi.exe
http://www.tribesnext.com
http://www.youtube.com/watch?v=D_nHrzNr6k0&feature=related
More specifically: http://xfer1.the-construct.net/tribes2/mods/Archive/
However Quantium is pretty old by today's standards, I think the servers are running a newer construction mod now-a-days.
If anyone is curious as to what game the OP is talking about, you can download it at the link below for free, then you have to download TribesNext:
http://xfer1.the-construct.net/tribes2/ : tribes2gsi.exe
http://www.tribesnext.com
http://www.youtube.com/watch?v=D_nHrzNr6k0&feature=related