Low Density of Compacted Specimens

“The density of my compacted specimens are low.  What causes this problem?”

A Potential Solution

Check the specimen diameter setting on your machine if you are using a Pine AFGC125X, AFG1, or an AFG2.    The AFGC125X can be set at 150 mm or 100 mm.  The AFG1 and the AFG2 allow for 150 mm, 100 mm, and 4 inch diameter molds.  Make sure it is set to the size specimen being compacted.

“No way!  I wouldn’t make that mistake.” you say.

You might be surprised how often this solves the problem.  It happens.  It’s okay.

The Solution Explained

Pine’s gyratory compactors apply a force to achieve the 600 kPa of pressure required by AASHTO T312 based on the specimen diameter.  A 100-mm specimen requires the application of 4,712.4 N of force to achieve 600 kPa of pressure.  A 150-mm specimen needs 10,602.9 N.  If one is compacting a 150-mm specimen but has the specimen diameter set to 100 mm in the control system, the machine applies a force of 4,712.4 N generating a pressure applied to the specimen of 266.7 kPa, only 44% of the required pressure.  This will always lead to an under-compacted specimen.

What Does Pine Recommend?

  1. Check the control settings in your gyratory compactor. Make sure they are correct.
  2. Contact Technical Support at 724-458-6393 or if the problem persists.

Want to Learn More?

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