Difference Between Standard Proctor Test  Vs Modified Proctor Test

Modified Proctor Test

The modified proctor test is known as a heavy compaction test for soil. A modified proctor test is usually used in situations where heavy compaction is required.

In 1933, Ralph R. Proctor of the University of California established a laboratory to obtain the practical maximum density of soil samples easily. The practical maximum density of the soil sample can be known along with the required moisture content in the soil.

This concept is known as the moisture-density relationship test or the standard proctor test.

During 1950, moving heavy Equipment were frequently demanding improvements to traffic pavements and clay subgrades. Sometimes the standard proctor values in compacted soil density tests were causing the pavements to be highly disrupted under the load to carry the increased forces.

The modified Proctor test with a high load on the ground was introduced in 1958 as ASTM D1557 and AASHTO T 180.

This article will learn about the difference between Modified Proctor Test and Modified Proctor Test and Standard Proctor Test.

Proctor Compaction Test

The Proctor Compaction Test is a laboratory method for experimentally determining the optimum moisture content. This test indicates the type of soil that will compact the most and attain its maximum dry density.

According to this test, the dry density of soil for a given compaction effort depends on the amount of water contained in the soil during compaction. This test is commonly referred to as the standard Proctor compaction test; His test was later updated to form the Modified Proctor Compaction Test.

What Is Modified Proctor Test?

Modified proctor test with changes in water content is widely used in determining the compaction of different types of soils and their properties.

Modified proctor compaction test showed a relationship between dry density and soil water content.

The main purpose of compaction is to increase the shear stress strength of the soil by reducing its permeability and compressibility.

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Purpose of Modified Proctor Test

1. This test is done to know the compaction capacity of the soil for road pavements for heavy vehicles.
2. The modified proctor test reduces the permeability of the soil as required by the compaction process.
3. Modified proctor test will help increase soil shear strength and soil bearing capacity through compaction to withstand heavy loads.
4. Due to the modified Proctor Test, the reduction in settlement of the structure after construction can be fixed.

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Need For Modified Proctor Test

• The bearing capacity of the soil should be considered during the construction of any structure or building.
• Proper inspection of the bearing capacity of the soil on-site should be done before starting any construction.
• There are only two solutions if the bearing capacity of the clay available for building on a site is less than required. The first solution is to increase the depth of the foundation so that the total load is transferred to the groundwater table.
• Another option is to improve the bearing capacity of the soil by various methods. Soil compaction is the simplest method of increasing soil capacity.
• Soil density can be increased by reducing air barriers in the soil compaction process.

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Modified Proctor Compaction Test Apparatus

The following are the different devices for the modified Proctor compaction test.

1. Cylindrical Metal Mould

These moulds have a diameter of 100 mm and a volume of 1000 cm. Or these moulds are 150 mm in diameter and 2250 mm in cubic cm.

2. Sample Extruder

A design made by fixing moulds together to extract a compacted sample.

3. Thermostatically Controlled Oven

To keep the soil sample at a temperature between 105 C and 110 C.

4. IS Sieve

75 mm, 19 mm, 37.5 mm

5. Balance of Capacity

6. Metal Frames

7. Mixing Tools

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Modified Proctor Test Procedure

The process of modified proctor test is followed step by step,

Step 1. About 5 kg of dry soil is sampled at the site.

Step 2. Take the appropriate sieve of the sample through a 19 mm sieve.

Step 3. Add water as required to the soil sample and mix.

Step 4. In sandy or gravel soil, about 3% to 5% water of the sample and for cohesive soil, 12% to 15% water of the sample is required.

Step 5. Take the weight of the empty mould and base plate in grams. Record the weight as W1.

Step 6. Attach another extension collar to the mould.

Step 7. Compact the sample of moist soil into the mould in about five layers.

Step 8. The soil is filled in each layer by compacting it 25 times using a 9 kg rammer.

Step 9. When compacting the rammer in the mould, its height should be a drop of about 450 mm from the ground so that it can be properly compacted to the soil sample.

Step 10. After the compaction process, remove the extension collar from the mould and level the top of the sample in the mould using a straightedge.

Step 11. Weigh the mould with the soil compacted in this way. And note this weight as W2.

Step 12. The compacted clay from the mould is extracted into a tray outside.

Step 13. Now a sample is taken for the moisture content of this sample. And this sample is placed in the oven.

Step 14. This way, at least 5 samples are tested. It is shown on the graph. Showing dry density and moisture content.

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Calculation of Modified Proctor Test

The bulk density Yw in g / cm3 of each compacted sample is calculated by the following formula

Is = (m2 – m1) / Vm

m1 = Weight of mould with the base plate,

m2 = Weight of mould with the compacted soil,

Vm = Volume of mould in cm3.

The dry density Yd of g / cm3 is calculated by the following formula

Yes = Yes / (1 + W / 100),

Ye = Bulk density,

W = % of moisture content.

The maximum dry density depends on the percentage of soil moisture, which will be noted as the maximum moisture content.

The maximum moisture content in the soil depends on the water content. Which helps to compress the soil to maximum density.

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Standard Proctor Test

The standard proctor test can be defined as a light compaction test. The use of standard proctor test is useful for road construction for schools, colleges.

In 1933, Ralph R. Proctor of the University of California established a laboratory to obtain the practical maximum density of soil samples easily. The practical maximum density of the soil sample can be known along with the required moisture content in the soil.

This concept is known today as the moisture-density relationship test or the standard proctor test.

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Difference Between Standard Proctor Test and Modified Proctor Test

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