paulharvey
Veteran Member
That and the hardness of the parent rock they are crushing. The test is call L.A. wear test. Put rock and steal balls in a revolving drum and see how much gets pounded to powder over a number of revolutions. Soft rock wears more then fifty percent.
LBR is what we use in Florida for base. Need an LBR-100 for use as base, but that along doesn't make a pit DOT certified. The actual DOT certified rock is sampled periodically by FDOT and outside labs. You can (I have) seen plenty of good rock that meets FDOT spec, but isn't FDOT certified do to expense; and the county and city didn't require it. We did require it met LBR-100; and pulled samples every 1/2 mile of road way. but more to the point several limerock mines kept a pile for city/county/engineered tested jobs, and another pile that was the cap they sold to anyone that didn't know the diffrence. It would have more clay balls, and overburden, but would still work for Joe blow home owner, just don't build a major highway with it.
LBR=Limerock bearing ratio
Here the abrasion test is done on asphalt aggregate