Only 25 years ago, the raw materials necessary to produce ready-mix concrete -- namely, cement, fly ash, and aggregates -- were far more available than they are now.  These materials were not only plentiful, but they were produced near the markets they serviced. The cement and aggregates industry employed many individuals with local, well-paying union jobs; in turn, local businesses benefited from the commerce these companies generated.  As an industry, we used these resources as if there were an infinite supply.  Need to strengthen your concrete?  Just add another sack of cement.  Need the concrete to set a little faster?  Just add more cement to the mix.