How do I perform a gravimetric analysis of Portland cement?
http://books.google.com/books?id=VeXQAAAAMAAJ&amp;pg=PA2&amp;lpg=PA2&amp;dq=Gravimetric+Analysis+of+Portland+Cement+%22aluminum 
Copy whole URL. Page 2 for clickable index, then page 18. 
DOI: 10.1039/AN9709500051

Digest it in "strong" HCl (tough lab for employment, worse if you service the fume hoods).  Everything except silica comes out as soluble chlorides (hydrated complex ions).  That says something about Portland cement in acid environments and, unless modified, in seawater.