1.3.2 Moisture Measurement
Moisture at 160 kg/m³ (10 pcf)
1.3.3 Calibration Method
The gauges are calibrated in accordance with the method recommended by
ASTM D6938, D7759, D2950 and AASHTO 310
. Five density standards
consisting of three metallic blocks of Magnesium, Magnesium/Aluminum
and Aluminum and two mineral blocks of Granite and Limestone to cover
the measurement range of 1100 to 2700 kgm³ (70-170 PCF). The density
of these standards has been determined to an accuracy of better than ±0.1
%. The working moisture standard has been calibrated against saturated
silica sand with an accuracy of better than ±0.5 % to cover the measurement
range of 0 to 640 kgm³ (0-40 PCF).
Four entirely different calibrations are available to the engineers or techni-
cians controlling the use of the gauge but they are not accessible to the
operator without use of a password. Two of these are adjustments to the
main calibrations to compensate for materials widely different from normal
soils. No additional equipment is required for the adjustment other than a
sample of the material at a known density. No additional equipment is re-
quired for an entirely new calibration other than a suitable set of standards.
Count rate data is converted to densities using USNIST gamma attenuation
coefficients and the known density of the standards.
1.3.4 Field Data Conversion
Wet Density
and
% Compaction (Marshall)
Dry Density
and
% Compaction (Proctor)
Moisture Content
and
% Moisture
Void Ratio
and
% Air Voids
1.3.5 Radiological
Gamma
Source
HSI
2200064
Amount and Type of Material
10 mCi (nom) cesium 137
Special Form Registration
USA/0634/S-96, USA/0356/S
ANSI and ISO Class
C66546
SLOW
4 min
NORMAL
1 min
FAST
15 sec
Precision kg/m³ (pcf)
± 2 (0.13)
± 4 (0.25)
± 8 (0.5)
Surface Error kg/m³ (pcf)
- 4 (0.25)
- 4 (0.25)
- 4 (0.25)
Depth
mm (inch)
100 to 200
(4 to 8)
100 to 200
(4 to 8)
100 to 200
(4 to 8)
4
