Refer to FAA Advisory Circular 150/5335-5, "Standardized Method of Reporting Airport Pavement Strength PCN". Also, if it's an existing runway, the airport's ALP should list it.
For airport pavement maintenance requirements, refer to FAA AC 150/5380-6A, "Guidelines and Procedures for Maintenance of Airport Pavements". That advisory circular (AC) may be available for download at FAA's website.