AASHTO T-304 Standard Method of Test for Uncompacted Void Content of Fine Aggregate
Analysis of AMRL Proficiency Test result data by David Jahn
confirmed that the biggest cause of variability between labs conducting
this test was the way in which the technician struck off the excess
material at the top of the cylinder in an attempt to level it.Not everyone was doing it exactly the same way, every time. Some
might not have the spatula blade perfectly perpendicular to the edge of
the cylinder, which could push material back down into the cylinder or
scoop it out at the end of the sweep.Others may have been holding the spatula higher at one end of the
blade than the other, which would leave an angled top cone on top of the
cylinder.What was needed was a way to position the edge of the spatula prior to the strike off to ensure that: A) The full edge of the spatula was horizontal, and B) Perpendicular to the edge of the cylinder.HMA Lab Supply is pleased to introduce our version of the Void
Content Apparatus with the David Jahn Modification. It works, it’s easy
to use, and it’s not expensive.The plate allows the technician to place the edge of the spatula
flat on the plate and push it across the material on top of the cylinder
without touching it and causing vibrations that would make the material
in the cylinder compact.What the means is that there will be far less variability between agencies and contractors.