THIN LAYER MEASUREMENTS
Conventional backscatter gauges measure density to depths of
approximately 4 inches. To perform readings on layers of asphalt
with thickness of 3.33 inches or less, use the following method
(formula):
WD – DB
×
K
DT =
1 – K
where:
DT = Overlay density
WD = Density read by gauge
DB = Bottom layer density
K = Effect of top layer thickness on the gauge
To use the above method of overlay measurement, follow the
procedure below:
Determine the density of the bottom layer (underlying material)
(DB).
Apply the thin lift overlay.
Determine the thickness of the overlay and select the
corresponding (k) value from Table 3–1 on page 3–14.
Measure the thin lift overlay density with the gauge in
backscatter position (WD).
Enter all values into the above equation and calculate the
overlay density (DT).
3–12
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