Standard Proctor Test: Understanding Compaction with Lab Report

Standard Procter Test

Standard Proctor Test is carried out to study or understand the soil’s compaction characteristics with variable moisture content.

The test is performed to estimate the maximum load the soil could bear hence ultimately reducing the voids present in the soil.

The Proctor Test is one of the basic tests carried upon soil while dealing with soil in geotechnical engineering. Being a basic and easy Proctor Test gives a reliable result for understanding the behavior of soil.

Read More: Standard Penetration Test (SPT Test) – Procedure, Test Report

What Is Compaction of Soil

Soil compaction is a process in which soil dissipates mechanical stress and condenses. The soil consists of solid particles and water or/and air-filled pots. A more detailed explanation of the three-phase nature of the soil is provided in the soil as a three-phase system. 

When subjected to stress, the soil particles are redistributed within the soil mass and the void volume decreases resulting in condensation. Mechanical stress can be applied through kneading, or by dynamic or static methods.

Benefits Of Compaction of Soil

The following are the major benefits of soil compaction,

• Increases bearing capacity and stability
• Permeability (hydraulic conductivity) decreases
• Freeze-melt cycles have reduced heating
• Erosion can be controlled
• Subscription down

History And Use Of Proctor Test

It has been known for a long time that soil moisture, especially Kosiv soils, has a direct effect on how efficiently it can be prepared by construction equipment.

Normally the soil is one of the natural materials and the ideal moisture content and maximum dry weight vary for each soil type, the best unit load and ideal moisture content questions cannot be answered.

Read More: Concrete Core Test | Concrete Core Test Procedure | Concrete Cores | Concrete Core Sample

Proctor Compaction Test

The proctor compaction test measures the maximum unit load that a particular type of soil can be compacted to use a controlled compact force at an optimal water content.

It is the most common laboratory soil test and is the basis for all engineered compact soil placements for embankments, pavements, and structural mills.

The results of the Proctor test are compared to the measured densities of the compacted-filled space to determine the degree of soil density.

The Proctor test was invented in 1930 by Ralph R. Proctor, a field engineer at the Bureau of Waterworks and Supplies in Los Angeles, California.

This process, which typically simulates in-situ compaction processes performed during the construction of earth dams or embankments, is the most common laboratory test conducted to achieve soil compressibility.

Read More: Specific Gravity of Soil Test with Sample Report

Proctor Compaction Test Apparatus

The following are the apparatus used in the proctor test of soil,

Cylindrical Metal Mold: having an internal diameter of 4” or 6”, an internal height of 4.6”; and the mold should have a detachable base plate & collar of 2 inches (5.08 cm).

Rammer: weighing 5.5 lbs (2.5 kg) & having a fall of 12 inches (30.5 cm), with a flat circular face of 2” diameter.

Sensitive Balance: sensitivity ranging from 0.1 gram to 1 gram.

Thermostatically controlled oven (105°C  +- 110°C)

• Steel straight edge.
• Moisture containers.
• Sieve No.4.
• Tray & scoop.
• Graduated cylinder.
• Mixing tools. (spoon, trowel, spatula).

Read More: Modified Proctor Test | Standard Proctor vs Modified Proctor | Modified Proctor Test Procedure

Standard Proctor Test Procedure pdf

The proctor test procedure is as follows,

• Collect soil sample weight of about 20 kg by passing it through the IS sieve 4.75 mm and 20 mm.
• Then find out the % of soil samples retain on 20 mm and 4.75 mm sieves. If the % of retained soil on the 4.7 mm sieve is more than 20 then choose 150 mm dia mold for the test and if the % of soil retained on the 4.7 mm sieve is less than 20% then choose 100 mm dia mold for a test.
• Now, combine the % soil passing through 4.75 mm and retain 4.75 together to prepare at least 16 to 18 kg of soil sample for test.
• Take a standard Procter test mold with a base plate dry it and clean it properly and apply slight grease inside.
• Measure the weight of the mold with the base plate at an accuracy of 1 gm. (W1)
• Collect 16-18 kg of soil sample and add water to bring water content in soil up to 4% for any soil and 8% for a clayed type of soil.
• Prepare at least
• 6-8 parts from a whole soil sample.
• Fix the collar on the mold and place it on a hard surface.
• Take 2.5 kg from the prepared soil sample and fill the mold in 3 equal layers such that each layer is about 1/3rd of the total height of the mold. Compact each layer with a rammer by giving 25 nos. of blows. The compaction by the rammer is done properly such that the rammer hits the entire area of mold filled with soil.
• Fill the mold up to the top of the collar attached. Once the soil is filled up remove the collar from the top of the mold.
• Cut down and remove extra soil outings from a mold with a straight edge.
• Now weight mold with soil sample as W2.
• Take out all soil samples from the mold.
• Collect at least 3 samples of soil for water content determination.
• Add 3% more water to the remaining soil sample and repeat the above steps.
• Do this with more 6%, 9%, and 12% water content and repeat the same steps.
• From water content, the weight of mould, and the weight of mold with soil find out the bulk density of soil.

Observations from Test

Dia. of the mold =

Mould Height =

Mould Volume, V=

Spe, the gravity of soil solids, G=

Observation Table:

Sr. No.	Descriptions	Sample No.
		1	2	3
Observations:
1.	Weight of mould with base plate
2.	Weight of mould with soil sample
Calculations:
3.	Weight of compacted soil M = (2) – (1)
4.	Bulk Density,
5.	Water content, w
6.	Dry Density,
7.	Void ratio,

where,

ρd = dry density of soil in kg/m3
Gs = specific gravity of the soil to be tested
ρw = density of water in kg/m3
w = water content in percent.

Soil Compaction Test Report

The following is the soil compaction test report,

Conclusion

In conclusion, the standard proctor test is a widely used method to determine the compaction characteristics of soils, and it provides valuable information for engineering projects and involving soil compaction, such as road construction, foundation and embankment.

Also the standard proctor test measures the maximum dry density and this information is crucial in designing proper compaction method to ensure the stability and load-bearing capacity of the soil.

The standard proctor test serves as a fundamental tool in geotechnical engineering and aiding in the selection and control of soil compaction process to achieve optimal result in projects.

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