Geo-technical Engineering

1. Experiment No.: 08 Date:
STANDARD PROCTOR TEST
Object and scope:
To determine the relationship between water content and dry density of soil using standard Proctor test
(light compaction) and then to determine the optimum water content and the corresponding maximum
dry density of soil. Also find relationship between penetration resistance and water content for the
compacted soil.
Reference:
IS: 2720 (Part -18) - 1965
Theory:
Soil which is natural material is used as construction material for construction of sub grades of roads,
embankments for roads and railways and earthen dams. Normally suitable type of soil is borrowed from
borrow pits located nearby and it is laid in layers of specified thickness, water is applied and rollers are
operated over the soil to compact it. This compaction process modifies its properties like density, voids
ratio, permeability, shear strength etc. Density achieved in the field depends upon the amount of water
added to the soil during compaction. At particular water content a given soil achieves maximum dry
density. Therefore the amount of water to be added must be estimated for the soil. This amount of water
at which a given soil can be compacted to maximum dry density is called optimum water content. This
optimum water content and maximum dry density are estimated using this test. These are called
compaction parameters of the soil.
During this test penetration resistance curve is also obtained using proctor needle which can be used in
field compaction control. The result of compaction test is also used to control the field compaction. The
water content and dry density of compacted soil in the field is obtained and the values are compared
with the test result. If the test result and field result are not confirming, then there must be modification
in amount of water to be added and number of passes of the compacting equipment.
Equipment:
1) Cylindrical metal mould of capacity 1000 cc, with an internal diameter of 100 ± 0.1 mm and an
internal effective height of 127.3 ± 0.1 mm or mould of density 2250 cc, with an internal diameter
150 ± 0.1 mm and internal effective height of 127.3mm ± 0.1 mm, each mould fitted with detachable
base and removable extension (collar) approx. 60 mm high.
2) Metal rammer 50mm diameter circular face, weighing 2.6 kg and having drop of 310 mm
3) Steel straight edge
4) 4.75 mm I.S. sieve
5) Balance 10 kg capacity sensitive to 1gm
6) Thermostatically controlled oven (105 -110ºC)
7) Water content container
8) Mixing equipment such as mixing pan, spoon, trowel, spatula
9) Measuring cylinder of 100ml capacity

2. Procedure:
1) Take a representative soil sample weighing approx. 20kg thoroughly mixed, air dried material
passing 4.75mm I.S. sieve. About 2.5 kg of soil is taken in six trays. Add enough water to bring its
water content to about 7% (sandy soil) or 10% (clayey soil) less than the estimate optimum moisture
content.
2) Clean the mould and fix it to the base. Take the empty mass of the mould and the base nearest to
1gm.
3) Attach the collar to the mould. The inside of the mould may be greased throughout.
4) Mix the matured soil throughout. Take out about 2.5 kg of the soil and compact it in the mould in
three equal layers. Each layer being given 25 blows from the rammer weighing 2.6 kg dropping from
a height of 310mm. Each layer of compacted soil should be scored sufficient to fill the mould
leaving about 5mm to be struck off when collar is removed. Find the penetration resistance of the
compacted soil, using the Proctor’s needle.
5) Remove the collar and cut the excess soil with the help of a straight edge. Clean the mould from
outside, and weigh it to the nearest gram. Eject out the soil, cut it in the middle and keep a
representative soil specimen for water content determination.
6) Repeat step 4 and 5 for about 5 or 6 times using a fresh part of the soil specimen.
Observation table:
Sr.
No.
Determination No. 1 2 3 4 5
A. Determination of density
1 Mass of empty mould M1 (kg)
2 Mass of mould + compacted soil M2 (kg)
3 Mass of compacted soil M=M2-M1 (kg)
4 Diameter of compaction mould d (m)
5 Height of compaction mould h (m)
6 Volume of compaction mould V (m3)
7 Bulk density γ = M/V ( kg/m3)
8 Load on proctor needle P ( kg)
9 C/S area of proctor needle used A (cm2)
10 Penetration resistance R=P/A ( kg/cm2)
B. Water content
1 Container No.
2 Mass of container m1( gm)
3 Mass container +wet soil m2 (gm)
4 Mass container +dry soil m3 (gm)
5 Water content ω (%)
6 Dry density γd (kg/m3)
Calculations:
The dry density of the compacted soil is
Dry density = γd = [
ϒ
1+0.01ω
]

3. A curve showing the relationship between dry density and water content is plotted. The water content
corresponding to maximum dry density is found from the curve which is optimum water content of soil.
On sample plot draw curve between penetration resistance and water content.
Result:
1) Optimum moisture content (OMC) =
2) Maximum dry density =

4. Fig. Standard Proctor test

5. Fig. Proctor Needle
Fig. Calibration Curve for Penetration Resistance, R