Somewhere in my library of old engineering information (Civil Eng. ?) there
is a description of "soil cement". I remember little of the details, but it
seems that the gist of the article, was about making roads from cement and
soil. The process was to remove an appropriate depth of soil - don't ask me
what is appropriate - and mix the soil 50/50 with cement and reapply to the
same area. Ergo, a roadway, above grade, and supposedly strong enough for
the traffic of the day.