Steve:
The material that was laid down is actually crushed concrete, first I had to add about 4 loads of dirt to help level things up a bit but still give it good drainage.
The crushed concrete was cheaper than say flexbase material. Only problem I found with it was it did have some trash in it, in which I was told this before I had it laid down. The guy I bought it from said usually you would find small pieces of re-bar and small black mat material in it. Usually the re-bar was so small that the magnet didn't catch it while being screened.
In my case I have yet to find any re-bar but did find some small pieces of the black mat along with baling wire,glass,pieces of small wood. Most of that comes to the top at first and easly picked up. The base has been down for about a year and half now and I have not found any trash on top in a long time.
I think it makes a very good base and has settled right in. My plan is to top it with a wash rock later on or possibly hot mix asphalt. I do have to spray it a couple times (yearly) with round-up to control the weeds and I do have a adbundance of bermuda grass that comes through also at times that I try to kill out.
Tony