Q.: Do you have to be certified to calibrate equipment used for air pressure in concrete?
A.: The short answer is “no, but ...” The process for calibrating a roll-a-meter is described in Section 5 of ASTM C173, “Standard Test Method for Air Content of Freshly Mixed Concrete by the Volumetric Method.” As often is the case, it lays out several parameters but also refers to a procedure outlined in another ASTM standard.
Section 8 of ASTM C29, “Standard Test Method for Bulk Density (“Unit Weight”) and Voids in Aggregate,” gives detailed instructions on how to calibrate a container. In the case of a roll-a-meter, it’s the bowl and calibrated cup that are being calibrated. Once that has been done, other parts of the roll-a-meter, such as the graduations on the neck, are checked for accuracy as outlined in C173.
Neither ASTM test method requires that the calibration be performed by a certified technician. However, the company or government entity ordering the test may well have certification requirements.
As an example, the materials testing and certification manual issued by the South Dakota Department of Transportation says, “Any individual, who is providing Acceptance, Quality Control, Quality Assurance or Independent Assurance testing of materials and/or acceptance inspection in the areas designated by this program shall be certified.” Specifically, SDDOT requires anyone testing concrete to be certified as an ACI Concrete Field Testing Technician–Grade I, as well as in several related SDDOT procedures. Calibration of the testing equipment is specifically listed under the quality control function, and is therefore also covered by the certification requirements.
So while anyone can calibrate a roll-a-meter, air entrainment test results may be accepted only when the device has been calibrated by a certified technician.