Gyratory Compactor Mold Measurement

Why Measure Molds?

First, AASHTO T 312 requires it.  Annex A of AASHTO T 312 describes the equipment and procedures required to properly measure molds.

Second, out-of-specification molds may cause density correlation problems that typically manifest themselves as high air void content.  High air void content may cause one to question gyratory compactor calibration and/or the mix design potentially costing one time and money.

Precision

Pine Test Equipment, Inc. offers a Mitutoyo 3-point bore gage and a master ring to measure internal mold diameter.  Pine’s field service technicians use this equipment to check molds as part of service package for a gyratory compactor.  Pine can also certify molds at the factory.

Standards

AASHTO T 312 Annex A

Bore Gage

The AFGM01 Bore Gage utilizes a three point contact system in conjunction with a digital micrometer head.  It includes an extension to provide an easy reach to the base of SGC molds and can be set to read in either millimeter or inch units.

Use the AFGM03 150 mm Master Ring to preset the gage to 150 mm.  First, retract the contact probes.  Second, insert the gage into the mold.  Next, turn the micrometer knob until the knob clicks.  And finally, read the diameter directly on the digital readout.

Master Ring

The AFGM03 150 mm Master Ring serves as the NIST-traceable  verification/calibration standard for the AFGM01 Bore Gage.  The Master Ring has a 3-year certificate and comes with spacers to help obtain repeatable positioning of the gage inside the mold bore as required by Annex A.