1. Specific Gravity of Soils

2. Specific Gravity
This number indicates how much heavier/lighter a material is than water.
In soils, SG refers to the mass of solid matter of a given soil sample as compared to an equal volume of water.

3. Specific Gravity
For example: A material with SG of 2 is twice as heavy as water (2x 62.4 lbs/ft3 ) = lbs/ft3
Equation Form: SG = Ms/VsΥwater
We use the SG of soils to calculate other engineering properties like the volume of solids in a sample….
This leads to the phase diagram (like last class) and…
S, n, e

4. Specific Gravity Soil Solids Water W = 187.2 lbs W= 62.4 lbs
SG= 187.2/62.4 = 3.0
1 ft3
1 ft3

5. General Ranges of SG For Soils
Sand – 2.67
Silt
Clay & Silty Clay
Organic Soils <2.0

6. Procedures For Specific Gravity Lab ASTM D 854
See Chapter 3, Page 55 For Your Data Sheet
APPARATUS:
500 ml flask
Ice
Heating Plate
Thermometer C
Scale (readability .1g)
Evaporating Dish
Distilled Water

7. Procedures (Method B) Dry specimens to constant mass in oven at 110 C.
Select a 500 ml flask and record mass (g)
Fill with distilled water to 500 ml line and record mass (g)
Record temperature of water in degrees Celsius (T1).
Pour 2/3 of water back into distilled container

8. Weigh out 100g of sandy soil and transfer to flask
Add distilled to 2/3 full and boil gently for 10 minutes
Bring temperature back to T1 using cooling bucket w/ice.
Add distilled to 500 ml line and record mass (g)
Record mass of evaporating dish (g)
Pour ALL sample into dish and dry to constant weight.
Record mass of oven dried dish/sample.
Complete calculations on data sheet, including correction for temperature …. SG is always reported at 20 C.
See page 44 for correction factors.