[M.D. Holloway]

Here are some good sites - you are better of looking into concrete than cement. Cement is something that holds concrete together.

http://www.concrete.com/index.htm

http://www.aci-int.org/general/home.asp

http://www.concretenetwork.com/

http://www.worldofconcrete.com/

I went to the World of Concrete trade show a few years ago - everything and anything you ever wanted to know.