On the subject of crushed brick -- the slave lodge and other buildings that I
excavated on an 18th century Cape wine estate in South Africa had floors of
crushed brick.  The brick was sometimes mixed with clay as a binder, but
other areas (especially outside the doorways, etc.) were paved with closely
packed brick crumbs.  In a couple of areas this surface had been plowed,
mixing the brick with the overlying strata, but it was pretty clear that the
plow had done this.  Areas paved with whole bricks that had been plowed were
quite distinct.  It seems to me that if you're coming up with only crushed
brick, and no whole bricks, you're probably looking at something that started
out crushed.  The plow will scar it, but unless there's been extremely
intensive plowing, there will still be some brick left intact or in course.
 
Good luck,
Ann