Aggregate and CSM requirements

The aggregate material for the CSMs may be select granular material, crushed or uncrushed gravel or stone, recycled aggregate, recycled crushed and graded Portland cement concrete, crushed and graded iron blast furnace slag or a combination thereof, as well as approved select soil. 

The aggregate requirements for CSMs, such as their mechanical and physical properties and the grading of the aggregate mix, are basically determined from federal or state relevant specifications. 

Generally speaking, the CSMs are required to have (a) some minimum compressive strength depending on the type of overlaying layers and hence type of pavement (flexible or rigid) and the importance of the layer in the pavement structure (base course or sub-base) and (b) freeze-thaw durability. 

Source Adapted from FAA, Advisory Circular, AC I50I5370-I0F, U.S. Department of Transportation, Federal Aviation 

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