Limited lab certifications are available for two materials areas:

• AASHTO T 310 (Nuclear Density of Soils)
• AASHTO T 152 (Concrete Air Content by the Pressure Method)

All procedures are the same for a limited laboratory certification as a full certification, providing a two-year certification alternative at a reduced fee for laboratories performing minimal testing.

Limited lab certification requests are most common for laboratories that perform only field densities for soil applications, and for concrete laboratories performing only slump, cylinder, and air (by pressure method). According to ARDOT, sampling (AASHTO R60), slump (AASHTO T119), and cylinders (AASHTO R100) must be performed by a certified technician, but are not required to be performed by a qualified laboratory. The air pressure method (AASHTO T152) does require laboratory certification, which may be obtained by the limited lab certification option. Thus, a laboratory completing the limited certification for concrete will also receive certification in R60, T119, and T23 at no additional charge – provided the equipment and records meet the certification requirements.

For limited lab certification inspections, every effort should be made to consolidate travel plans with another laboratory inspection trip. Because the equipment check is minimal, the laboratory may also elect to bring the pertinent equipment and quality manual to CTTP, or other mutually agreeable location, for the inspection in order to expedite the certification process.