The demonstration and subsequent analysis showed that while the overhead of a second machine had been added to the crushing process, the cost per ton of crushed concrete decreased. Costello and Doab repeatedly crunched the numbers with David McAfee until there was no question in his mind.
The best gravel to leave exposed for a long time is (recycled asphalt product), a great product on any driveway. It cost less because it is a recycled blend of crushed asphalt, crushed concrete and crushed brick. I have found it to be a great base for paving or to leave exposed.