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The Virginia Highway Research Council developed and alternate
method to take advantage of the fast testing capability of the
instrument. The procedure involves the use of a control strip.
While originally developed for paving, it is often used on plant-
mixed base material.
The typical procedure involves the selection of a test site 100
meters (300 feet) long and the width of the paver. Compaction is
accomplished with rollers and a nuclear density gauge is used to
measure density between passes of the roller. From this
information a roller pattern is established as shown in Figure 4.
Compaction is continued until there is no further increase in
density. At this point, the maximum density is determined by
taking the average of 10 randomly selected sites on the control
section.
Using this method, the specifications for the project are
normally established as 98% of the control section density.
Tests are usually run on 2800 square meter (2800 square yard)
sections and the average of five tests used to establish passing
conditions for each section. Each test must be 95% or over and
the average must be 98% or over.
A new control section must be established when the material
source has changed or after 10 test sections have been
approved.
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