In a message dated 11/30/99 2:43:21 PM Mountain Standard Time, [log in to unmask]
writes:

<< Hello HISTARCHERS,
 I've been approached about an issue probably more architectural than
 archaeological, but wondered if anyone could help.  A colleague wants to
 know if there is a chronology for
 concrete or any other way to date it.   Not really within my ken, sad to
 say.  Any ideas?
 Thanks, M.
  >>

I have been looking into this, off and on, over the last several years, Mary.
 In fact, I am currently attending a state transportation conference here in
Ogden where there are many concrete companies who I am talking to.  The best
research direction that we have found so far is following the evolution of
"rebar" that strengthens structural concrete - such as in bridges, house
foundations, and large concrete pipe.  We have determined that smooth
rectangular rebar was used in bridge construction in 1912 and that ribbed
rectangular rebar dates to at least the 1930s.  I am talking with some rebar
manufacturers at the meeting here about this very subject.  I will get back
to the list if something of value emerges.

Mike Polk
Sagebrush Consultants, L.L.C.
Ogden, Utah