1
Civil & Environmental Engineering Department
HYDROMETER ANALYSIS (ASTM D 422)
Application
Hydrometer analysis is done to measure the proportion of particles smaller than
0.075 mm.
Equipment
ASTM 152H Hydrometer
Mixer cup
Two 1000 cc graduated cylinder
Thermometer
Constant Temperature Bath
Sodium hexametaphosphate
Spatula
Beaker
Balance
Squeeze bottle
Rubber Stopper
Procedure
1.
2.
3.
4.
5.
6.
7.
8.
9.
Combine 50g (Md) of the soil passed through #40 sieve with 125 ml of sodium
hexametaphosphate solution (4%) in a 250 ml glass beaker. Allow the mixture to
soak for 16 hours (for demonstration today, 30 minutes will be enough).
Transfer all of the mixtures to an ASTM D422-specified dispersion cup. Wash
all the soil solids from inside of the beaker into the dispersion cup. Fill the cup
with water (half of the cup).
Stir the mixture with a mechanical stirrer at the rate of 10,000 rpm for one
minute.
Pour the slurry into a 1000 ml etched cylinder and fill with distilled water to
just below the etch mark. Wash all the slurry from cup into the cylinder using
squeeze bottle.
Using a rubber stopper, mix the soil water mixture by turning it upside down and
back at a rate of 1 turn per second for 1 minute.
Set the cylinder on a water bath (or table) and start the timer immediately.
Wash the remaining soil off the stopper and lip of the cylinder with the squeeze
bottle and fill the cylinder to the etch mark with distilled water.
Insert the hydrometer slowly and take the first hydrometer reading at 2 min,
with subsequent readings at 5, 15, 30, 60, 240, and 1440 minutes. The
hydrometer reading is taken at top of the meniscus.
Remove the hydrometer after each reading, and place it in a 1000 ml cylinder
filled with distilled water between readings. Spin the hydrometer in the watercylinder to take off the adhered soil particles.
Record the temperature of the mixture.
EGCE 324L (Soil Mechanics Laboratory)
Instructor: Binod Tiwari, PhD
Spring 2008
Date: 2/4/2008
2
Civil & Environmental Engineering Department
Calculations
1.
Calculate diameter of particle at time t.
D=k
L
t
K can be calculated for given Gs and temperature using Table 1.
L (in cm) = 16.3 – 0.463 R
2. Percentage passing for the specific diameter is calculated as,
P' =
( R − b) a
× 100%
Md
Values of a and b can be calculated using Table 2.
3. Calculate overall % passing as,
P = P'× P− # 40
Table 1 Value of K for different Gs and Temperature
EGCE 324L (Soil Mechanics Laboratory)
Instructor: Binod Tiwari, PhD
Spring 2008
Date: 2/4/2008
3
Civil & Environmental Engineering Department
Table 2 Values of Correction Factors a with Gs
Gs
2.5
2.55
2.6
2.65
2.7
2.75
2.8
2.85
a
1.03
1.02
1.01
1.00
0.99
0.98
0.97
0.96
Table 3 Values of Correction Factors b with temperature
Temperature
(oC)
17
18
19
20
21
22
23
24
EGCE 324L (Soil Mechanics Laboratory)
Instructor: Binod Tiwari, PhD
b
5.9
5.6
5.3
5.0
4.7
4.4
4.1
3.8
Spring 2008
Date: 2/4/2008
4
Civil & Environmental Engineering Department
GRAIN SIZE ANALYSIS – HYDROMETER MEASUREMENT (ASTM D422)
LABORATORY DATA SHEET
I. GENERAL INFORMATION
Tested by:
Lab partners/organization:
Client: CSUF CEED
Boring no.: N/A
Recovery date: N/A
Soil description:
Date tested:
Project: EGCE 324L
Recovery depth: N/A
Recovery method: N/A
II. TEST DETAILS
Hydrometer manufacturer/serial no.:
Mixer manufacturer/serial no.:
Scale type/serial no./precision:
Duration of initial soaking period:
Concentration of sodium hexametaphosphate solution: 4%
Dry mass of soil used (Md):
Specific gravity of soil solids:
Temperature:
K:
a:
Notes, observations, and deviations from ASTM D422 test standard:
b:
III. MEASUREMENTS AND CALCULATIONS
Clock Time
(hh:mm:ss)
t
(min)
R
L
(cm)
D
(mm)
P’
(%)
P
(%)
IV. EQUATION AND CALCULATION SPACE
L = 16.3 – 0.163R
( R − b )a
P' =
x 100%
Md
EGCE 324L (Soil Mechanics Laboratory)
Instructor: Binod Tiwari, PhD
D=K L/t
P = P’(P-#40)
Spring 2008
Date: 2/4/2008