Humboldt H-3750.5F Relative Density Apparatus - Manual (Page 3)

g) Dial Indicator Gage Holder.
h) Dial Indicator.
i) Calibration Bar.
Calibration
Determine the volume of the mold by direct measurement and check the
volume by filling with water as provided in a).
Determine the initial dial reading for computing the volumes of the specimen
as provided in b).
a) Volume by Direct Measurement. Determine the average inside diameter
and height of the mold to 0.001 inches. Calculate the volume of the
0.1 cu ft mold to the nearest 0.0001 cu ft and the 0.5 cu ft mold to the
nearest 0.0001 cu ft. Calculate also the average inside cross-sectional
area of the mold in square feet.
b) Initial Dial Reading. Determine the thickness of the surcharge base plate
and the calibration bar to 0.001 inches using a micrometer. Place the
calibration bar across a diameter of the mold along the axis of the guide
brackets. Insert the dial indicator gage holder in each of the guide brackets
on the measure with the dial gage stem on top of the calibration bar and on
the axis of the guide brackets. The dial gage holder should be placed in the
same position in the guide brackets each time by means of matchmarks on
the guide brackets and the holder. Obtain six dial indicator readings, three
on the left side and three on the right side, and average these six readings.
Compute the initial dial reading by adding together the surcharge base
plate thickness and the average of the six dial indicator readings and
subtract the thickness of the calibration bar. The initial dial reading is
constant for a particular measure and surcharge base plate combination.
Sample
Select a representative sample of soil. The weight of sample required is
determined by the maximum size of particle as follows:
Maximum Size
of Soil Particle
Weight of Sample
Required
(lb.)
Pouring Device to be used
in Minimum Density Test
Size of Mold
to be used
(cu. ft.)
3 inch 100 Shovel or extra large scoop 0.5
1 – ½ inch 25 Scoop 0.1
3/4 inch 25 Scoop 0.1
3/8 inch 25
Pouring Device
(1" diameter spout)
0.1
No 4 (4.75 mm) 25
Pouring Device
(1/2" diameter spout)
0.1