3. Proctor Compaction Test
Compaction test of soil is carried out using Proctor’s test to understand compaction
characteristics of different soils with change in moisture content. Compaction of soil is the
optimal moisture content at which a given soil type becomes most dense and achieve its
maximum dry density by removal of air voids.
Factors affecting compaction: 1- Moisture content 2- Soil type 3- Compaction effort (energy per
unit volume), There are two types of compaction test: 1- Standard proctor compaction test 2-
Modified proctor compaction test.
Part one: Standard proctor compaction test
For construction of highways, airports, and other structures, it is often necessary to compact soil
to improve its strength. Proctor (1933) developed a laboratory compaction test procedure to
determine the maximum dry unit weight of compaction of soils which can be used for
specification of field compaction. This test is referred to the standard Proctor compaction test
and is based on the compaction of the soil fraction passing No.4.
Equipment:
1- Compaction mold.
2- No.4 sieve
3- Standard Proctor hammer (5.5)lb. (24.5)N
4- Pan
5- Jack
6- Steel straight edge
7- Moisture cans
8- Drying oven
9- Plastic squeeze bottle with water.
Standard Proctor Compaction Mold and Hammer
A schematic diagram of the Proctor compaction mold, which is 4in. (101.6mm) in diameter and
(4.58in.) (116.4in) height is shown in Figure below. There is a base plate and an extension that
can be attached to the bottom and top of the mold, respectively. The inside volume of the mold
is (1/30) ft3 (943.9 cm3). The hammer can be lifted and dropped through a vertical distance of
(12 in) (304.8 mm).
, Procedure:
1. Obtain about 10 lb. (4.5 kg) of air-dry soil on which the compaction test is to be conducted.
Break all the soil lumps.
2. Sieve the soil on a No.4 sieve. Collect all of the minus-4 material in a large pan.
3. Add enough water to the minus-4 material and mix it in thoroughly to bring the moisture
content up to about 5%.
4. Determine the weight of the Proctor mold + base plate (not the extension), W1.
5. Now attach the extension to the top of the mold.
6. Pour the moist soil into the mold in three equal layers. Each layer should be compacted
uniformly by the standard Proctor hammer 25 times before the next layer of loose soil is
poured into the mold.
Note: The layers of loose soil that are being poured into the mold should be such that, at the end
of the three-layer compaction, the soil should extend slightly above the top of the rim of the
compaction mold.
7. Remove the top attachment from the mold. Be careful not to break off any of the compacted
soil inside the mold while removing the top attachment.
8. Using a straight edge, trim the excess soil above the mold. Now the top of the compacted soil
will be even with the top of the mold.
9. Determine the weight of the mold + base plate + compacted moist soil in the mold, W2.
10. Remove the base plate from the mold. Using a jack, extrude the compacted soil cylinder
from the mold.
11. Take a moisture can and determine its mass, w1.
12.From the moist soil extruded in Step 10, collect a moisture sample in the moisture can and
determine the mass of the can + moist soil, w2.
13. Place the moisture can with the moist soil in the oven to dry to a constant weight.
14. Break the rest of the compacted soil (to No.4 size) by hand and mix it with the leftover moist
soil in the pan. Add more water and mix it to raise the moisture content by about 2%
15. Repeat Steps 6 through 14. In this process, the weight of the mold + base plate + moist soil
(W2) will first increase with the increase in moisture content and then decrease. Continue the
test until at least two successive down readings are obtained.
16. The next day, determine the mass of the moisture cans + soil samples, w3.
Compaction test of soil is carried out using Proctor’s test to understand compaction
characteristics of different soils with change in moisture content. Compaction of soil is the
optimal moisture content at which a given soil type becomes most dense and achieve its
maximum dry density by removal of air voids.
Factors affecting compaction: 1- Moisture content 2- Soil type 3- Compaction effort (energy per
unit volume), There are two types of compaction test: 1- Standard proctor compaction test 2-
Modified proctor compaction test.
Part one: Standard proctor compaction test
For construction of highways, airports, and other structures, it is often necessary to compact soil
to improve its strength. Proctor (1933) developed a laboratory compaction test procedure to
determine the maximum dry unit weight of compaction of soils which can be used for
specification of field compaction. This test is referred to the standard Proctor compaction test
and is based on the compaction of the soil fraction passing No.4.
Equipment:
1- Compaction mold.
2- No.4 sieve
3- Standard Proctor hammer (5.5)lb. (24.5)N
4- Pan
5- Jack
6- Steel straight edge
7- Moisture cans
8- Drying oven
9- Plastic squeeze bottle with water.
Standard Proctor Compaction Mold and Hammer
A schematic diagram of the Proctor compaction mold, which is 4in. (101.6mm) in diameter and
(4.58in.) (116.4in) height is shown in Figure below. There is a base plate and an extension that
can be attached to the bottom and top of the mold, respectively. The inside volume of the mold
is (1/30) ft3 (943.9 cm3). The hammer can be lifted and dropped through a vertical distance of
(12 in) (304.8 mm).
, Procedure:
1. Obtain about 10 lb. (4.5 kg) of air-dry soil on which the compaction test is to be conducted.
Break all the soil lumps.
2. Sieve the soil on a No.4 sieve. Collect all of the minus-4 material in a large pan.
3. Add enough water to the minus-4 material and mix it in thoroughly to bring the moisture
content up to about 5%.
4. Determine the weight of the Proctor mold + base plate (not the extension), W1.
5. Now attach the extension to the top of the mold.
6. Pour the moist soil into the mold in three equal layers. Each layer should be compacted
uniformly by the standard Proctor hammer 25 times before the next layer of loose soil is
poured into the mold.
Note: The layers of loose soil that are being poured into the mold should be such that, at the end
of the three-layer compaction, the soil should extend slightly above the top of the rim of the
compaction mold.
7. Remove the top attachment from the mold. Be careful not to break off any of the compacted
soil inside the mold while removing the top attachment.
8. Using a straight edge, trim the excess soil above the mold. Now the top of the compacted soil
will be even with the top of the mold.
9. Determine the weight of the mold + base plate + compacted moist soil in the mold, W2.
10. Remove the base plate from the mold. Using a jack, extrude the compacted soil cylinder
from the mold.
11. Take a moisture can and determine its mass, w1.
12.From the moist soil extruded in Step 10, collect a moisture sample in the moisture can and
determine the mass of the can + moist soil, w2.
13. Place the moisture can with the moist soil in the oven to dry to a constant weight.
14. Break the rest of the compacted soil (to No.4 size) by hand and mix it with the leftover moist
soil in the pan. Add more water and mix it to raise the moisture content by about 2%
15. Repeat Steps 6 through 14. In this process, the weight of the mold + base plate + moist soil
(W2) will first increase with the increase in moisture content and then decrease. Continue the
test until at least two successive down readings are obtained.
16. The next day, determine the mass of the moisture cans + soil samples, w3.
