EXPERIMENT (2)
SPECIFIC GRAVITY DETERMINATION
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By:
Eng. Othman Tayeh.
Eng. Doaa Safi.
Test Designation
ASTM D-854; AASHTO T-IOO
PURPOSE:

Determine the specific gravity of soil which
is important in calculating void ratio, porosity,
unit weight, degree of saturation ……etc.
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DEFINITIONS :
The specific gravity of a given material is defined as the
ratio of the weight of a given volume of the material to
the weight of an equal volume of distilled water. In soil
mechanics, the specific gravity of soil solids (which is
often referred to as the specific gravity of soil) is an
important parameter for calculation of the weightvolume relationship. Thus specific gravity, Gs is defined
as
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where
. W= mass of soil solids (g)
. V= volume of soil solids (cm3)
. Pw= density of water (g/cm3).
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
The general ranges of the values of Gs for various
soils are given in the following Table:
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APPARATUS
1. Volumetric flask (500 ml)
2. Thermometer
3. Balance sensitive up to 0.01 g
4. Distilled water
5. Bunsen bumer and a stand (and/or vacuum
pump or aspirator)
6. Evaporating dishes
7. Spatula
8. Plastic squeeze bottle
9. Drying oven
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PROCEDURES :
1. Clean the volumetric flask well and dry it.
2. Carefully fill the flask with de-aired, distilled
water up to the 500 ml mark (bottom of the
meniscus should be at the 500 ml mark).
3. Determine the mass of the flask and the water
filled to the 500 ml mark (W1)
4. Insert the thermometer into the flask with the
water and determine the temperature
of the water
5. Put approximately 100 grams of air dry soil into
an evaporating dish.
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6. If the soil is cohesive, add water (de-aired and distilled) to the
soil and mix it to the form of a smooth paste. Keep it soaked for
about one-half to one hour in the evaporating dish. (Note: This
step is not necessary for granular, i.e., noncohesive, soils.)
7. Transfer the soil (if granular) or the soil paste (if cohesive) into
the volumetric flask.
8. Add distilled water to the volumetric flask containing the soil
(or the soil paste) to make it about two-thirds full.
9. Remove the air from the soil-water mixture. This can be done
by:
a. Gently boiling the flask containing the soil-water mixture for
about 15 to 20 minutes. Accompany the boiling with continuous
agitation of the flask. (If too much heat is applied, the soil may
boil over.) Or
b. Apply vacuum by a vacuum pump or aspirator until all of the
entrapped air is out.
This is an extremely important step. Most ofthe errors in the
results of this test are due to entrapped air which is not removed.
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10. Bring the temperature of the soil-water mixture in the
volumetric flask down to room temperature, i.e., T1-see Step 4.
(This temperature of the water is at room temperature.)
11. Add de-aired, distilled water to the volumetric flask until the
bottom of the meniscus touches the 500 m1 mark. Also dry the
outside of the flask and the inside of the neck above. the meniscus.
12. . Determine the combined mass of the bottle plus soil plus
water (W2).
13. Just as a precaution, check the temperature of the soil and
water in the flask to see if it is
or not.
14. Pour the soil and water into an evaporating dish. Use a plastic
squeeze bottle and wash the inside of the flask. Make sure that no
soil is left inside.
15. Put the evaporating dish in a oven to dry to a constant weight.
16. Determine the mass of the dry soil in the evaporating dish
(Ws).
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CALCULATIONS

Calculate the specific gravity
Specific gravity is generally reported on the value
of the density of water at 20°C. So
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
The values of A are given in the following Table
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At least three specific gravity tests should be conducted. For correct
results, these values should not vary by more than 2 to 3%. A
sample calculation for specific gravity is shown in the Table.
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PART 2 : UNIT WEIGHT DETERMINATION
ASTM D7263
PURPOSE:

To determine the unit weight of soil which is
used for determining weight-volume relationship.
Knowing the weight of soil is very important for
design of structures exposed to soil stress as
retaining walls.
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DEFINITIONS :

Unit weight ( ): the weight per unit volume.
APPARATUS :
1- Sensitive balance.
2- Wax (  = 0.9 g/cm3)
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PROCEDURES :
1- Prepare a sample of soil from the field and weigh
it (Msoil).
2- Immerse the sample in melted wax and weigh it
covering with wax (Msoil + wax).
3- Submerge the sample covering with wax in
water and weigh it
(Msoil + wax (sub))
4- Calculate the unit weight of the sample.
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Wsoil = Msoil * 9.81
 Vsoil = Vsoi + wax – Vwax
 Vsoil = Vsoi + wax – Vwax
 Vsoi + wax = Msoil + wax - Msoil + wax (sub)
 Vwax = M

wax
 wax
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