What Is Standard Proctor Test?
Standard Proctor Test is performed to understand the characteristics of different types of soil.
The standard proctor test is performed on the field to find the relationship between optimum moisture content and maximum dry density.
In Standard Proctor Test, the dry density of soil is obtained by varying the soil volume in a cylinder of size 1000 c.c with different water volumes and standard compaction forces.
The standard proctor test is a basic test for soil compaction to know soil characteristics in geotechnical engineering. The standard proctor test is simple and gives useful results for understanding the behaviour of soil.
History of Standard Proctor Test
In the early 1930s, to determine the maximum density of soil, Ghayttha discovered that in controlled environments (or within control volumes), soils could be compacted. As a result, the effects of soil in different conditions can be simulated by completely removing air from the soil.
In the standard Proctor Test, the soil can be effectively prepared by construction equipment to get the dry density of the soil.
Uses of Standard Proctor Test
- Standard proctor test is used to study other properties of on-site soil such as compressibility, porosity, strength, etc.
- Standard Proctor Test is used to identify the bearing capacity of the land for the construction of highways, foundations, embankments, pavements and gravity dams.
Standard Proctor Compaction Test
The standard Proctor compaction test measures the maximum unit load for clay. In which proper compaction of soil can be done using the optimum amount of water and controlled compact force.
The standard Proctor Test is usually a field soil test. It is a standard proctor test for embankment, pavements and structural mills.
The standard Proctor test was invented in 1930 by a California field engineer. It Was performed by Ralph R. Proctor. This is known as the Standard Proctor Test.
The Standard Proctor test is commonly used for the construction of earthen dams and embankments. This test is a common way to achieve soil compaction.
Compaction is the process of making the soil more solid by reducing the air voids. The degree of soil compaction for this test is measured in terms of dry density.
Dry density depends on the maximum water content. Maximum dry density and maximum water content are obtained for on-site soil compaction. For that, a curve is drawn between the water content and the dry density by various sample tests.
Dry Density of Soil:
M = total mass of the soil
V= volume of soil,
w= water content.
Standard Proctor Compaction Test Apparatus
The Apparatus for standard proctor test for soil compaction test is as follows:
1. Cylindrical Metal Mold:
Diameter = 4”,Height =4.6″
Rammer weighs 5.5 lbs (2.5 kg) and falls 12 inches (30.5 cm), 2 “diameter flat circular surface.
3. Sieve No.4.
4. Sensitive Balance:
sensitivity Balance is ranging from 0.1 gram to 1 gram.
5. Steel straight edge
6. Thermostatically controlled oven (105°C +- 110°C)
7. Tray & scoop.
8. Graduated cylinder.
9. Mixing tools. (spoon, trowel)
Procedure of Standard Proctor Test
- About 20 kg of air-dry soil is sampled for the standard proctor test of on-site soil. The sample is then sieved through a 20mm and 4.7mm sieve.
- In the next step, the soil sample is calculated as the percentage of soil retain on 20 mm and 4.75 mm sieve. And 4.75 The percentage of soil passing through the sieve is calculated.
- If the percentage of ratain from a soil sample on a 4.75 mm sieve is more than 20, then a 150 mm diameter mould is used for the test. If the percentage of the quantity of rain from a soil sample on a 4.75 mm sieve is less than 20%, a 100 mm diameter mould is used.
- The mould and base plate are properly cleaned and dried. Also, oil is applied to the inside surface of the mould.
- Weigh the mould for this test to the nearest 1 gram with the base plate.
- Then take a soil sample of about 16 kg. If the soil is sandy, add 4% water content to the soil sample and if the soil is clay, add about 8% water to the sample.
- Mix the sample clay well in water. The clay of this sample is divided into 6 to 8 equal parts.
- Fix the mould with the base plate and attach the collar to the mould.
- Now, put about 2.5 kg of water mix clay in the mould in 3 equal layers. Compact each layer in the mould by giving 25 strokes of the rammer. During compact, the surface of each layer should be evenly distributed in the mould.
- Rough the top surface of the first layer before placing the second layer in the layer. The second layer is then also compacted by 25 blows of the rammer into the mould. The third layer is compacted by placing it in the mould as above.
- The amount of clay used as the soil sample should be sufficient to fill the empty space of the mould. The collar is removed from the mould when the soil in the mould is completely filled.
- Remove the collar from the mould. And cut off the excess clay on top of the mould using a straight edge.
- Now clean the outer surface of the base plate and mould filled with clay. Measure its weight in the nearest gram
- Now, the clay is removed from the mould.
- Take at least 3 soil samples to determine the optimum amount of water.
- Then add 3% more water to the clay sample and repeat the steps as above.
Observations from Test
- Mould Volume, V=
- Mould Height =
- Dia. of the mould =
- Spe, the gravity of soil sample G=
Important Points for Standard Proctor Test
1. Optimum Moisture Content
The optimum moisture content indicates the maximum moisture content in the soil. Through which the soil for plowing achieves maximum dry density. This OMC value is the maximum amount of water given during compaction applied to the soil.
2. Maximum Dry Density
The dry density of soil obtained during optimum moisture contents is called maximum dry density.
3. Zero air void line
If complete air can be expelled from the soil during soil compaction, the soil achieves maximum dry density. This type of soil condition is called zero air cancellation dry density.
It is impossible to obtain complete dry density by soil compaction.
Compaction is the process of increasing the density of soil using a mechanical machine. Compaction causes rearrangement of clay particles and reduction in the void.
Properly compacted soil has very low voids resulting in a higher unit weight of the soil. In the natural state, the soil particles are loosely bound to each other. As a result, proper compaction is required to increase the bearing capacity in natural soils.
Also Read : What Is Modified Proctor Test? | Purpose of Modified Proctor Test | Modified Proctor Compaction Test Apparatus | Modified Proctor Test Procedure | Calculation of Modified Proctor Test | Difference Between Standard Proctor Test Vs Modified Proctor Test
Advantages & Disadvantages of Standard Proctor Test
Advantages of Standard Proctor Test
- The standard Proctor Test gives information about the water content in the soil along with the dry unit weight required for the compaction process.
- The standard proctor test provides information on the load-bearing capacity of the soil on site.
- The standard proctor test helps to determine the degree of density for the filling material for compact soil.
- Due to the standard Proctor Test, erosion of pavement can be controlled using compacted soil required in various engineering works.
Disadvantages of Proctor Test
- According to the information given after performing the standard Proctor Test, voids cannot be completely removed from the soil.
- The standard proctor test cannot be used for the construction of a heavy structure.