I've never heard of the stuff before, but a quick look using the Google search engine brought me to Stampcrete.com. If you go to that website and follow the link to "architects/engineers" and then to "technical data" (bottom of the page), you'll find the specifications for the concrete mixture. The company's website suggests that for "freeze/thaw" areas (where concrete may undergo the worst conditions) the mix spec should be 3500psi. I've got no idea where your contractor got the 7000psi number, but that type of concrete is pretty unusual. I've dealt with 5000psi concrete in much of the construction I've been involved with over the last 33 years, and even that strength is limited to a fairly specialized area...and it's not the driveway area, either.

[This message has been edited by treebeard (edited April 03, 2003).]

I'm in a NYC suburb. A freeze/thaw climate. All sidewalks and driveways are poured with 3000psi or 3500 psi concrete. Given a close friend is an architect and another a bldg dept consultant, I know the psi numbers above are accurate.

The Stampcrete is somewhat popular here, and the contractor I hired explained that fibers are added to the mix, bringing up the psi to 7000.

Phil