Determination of dry density and optimum moisture content by Standard proctor test

Standard proctor compaction method

standard proctor test

Determination of maximum dry density and optimum moisture content.

Aim:

To determine the optimum content and maximum dry density of a soil sample by standard proctor test.

Specification:

The experiment is conducted as per IS 2720-7(1980).

Equipments Required:

  • Proctor mould having a capacity of 1000cc with an internal diameter of 100mm and effective height of 127.3mm. The mould shall have a detachable collar assembly and detachable base plate.
  • Rammer: A mechanical operated metal rammer of weight of 2.6Kg , drop of 310mm. The rammer shall be equipped with a suitable arrangement to control the height of drop to free fall.
  • Sample extruder.
  • Balance of 15Kg capacity.
  • Sensitive balance.
  • Straight edge.
  • Graduate cylinder.
  • Mixing tools such as mixing pan, spoon, trowel, and spatula.

Theory:

Compaction is the application of mechanical energy to a soil so as to rearrange its particles and reduce the void ratio. It is applied to improve the properties of an existing soil or in the process of placing fill such as in the construction of embankments, road bases, runways, earth dams, and reinforced earth walls. Compaction is also used to prepare a level surface during construction of buildings. There is usually no change in the water content and in the size of the individual soil particles.

The objectives of compaction are:

  1. To increase soil shear strength and therefore its bearing capacity.
  2. To reduce subsequent settlement under working loads.
  3. To reduce soil permeability making it more difficult for water to flow through To assess the degree of compaction, it is necessary to use the dry unit weight, which is an indicator of compactness of solid soil particles in a given volume. The laboratory testing is meant to establish the maximum dry density that can be attained for a given soil with a standard amount of compactive effort.

To assess the degree of compaction, it is necessary to use the dry unit weight, which is an indicator of compactness of solid soil particles in a given volume. The laboratory testing is meant to establish the maximum dry density that can be attained for a given soil with a standard amount of compactive effort.

Precautions:

  • Thoroughly breakup the sample by running it through the screen before compacting it in the mould.
  • Pound within a moisture range from optimum to 4 percent below optimum. The closer to optimum the moisture content is, the more accurate the test will be.
  • Make sure the clamp on each mold section is tight.
  • Make sure the wing nuts on the base plate are secured with equal tension.
  • Place the mould on a solid block that is supported on firm soil or pavement.
  • Hold the rammer vertically so that it will fall freely.
  • Drop the 25 kg rammer weight freely
  • Use exactly 25 blows on each layer.
  • Place 3 equal layers in the mold

Procedure:

  1. Take a representative oven-dried sample, approximately 3Kg in the given pan. Thoroughly mix sample with sufficient water to dampen it to approximately four to six percentage below optimum moisture content.
  2. Weigh the proctor mould with base plate (W1). Fix the collar and base plate. Place the soil in the proctor mould and compact it in three layers giving 25 blows per layer with the 2.6 Kg rammer falling through a height of 310mm.
  3. Remove the collar, trim the compacted soil evenly with the top of the mould by means of straight edge and weigh.
  4. Divide the weight of the compacted specimen and record the result as the wet weight (γwet )gms/ cm3 of the compacted soil.
  5. Remove the sample from the mould and slice vertically through and obtain a small sample for moisture determination.
  6. Thoroughly break up the remainder of the material and add water in sufficient amounts to increase the moisture content of the soil sample by one or two percentage. Finally, repeat the above procedure for each increment of water added.
  7. Plot a graph between water content (w) and maximum dry density (γdry )gms/cm3 which exhibits optimum moisture content (OMC).
  8. Continue this series of determination until there is either a decrease or no change in the wet unit weight of the compacted soil.

Observation:

Height of mould ( H ) = _____________.

Diameter mould ( d ) = _______________.

Volume of mould (V) =(πd2)/4 x H= ______________.

Table: Weight of Soil for varying water content

Serial No. Details Test No.1 Test No.2 Test No.3 Test No.4
1. Weight of mould with base plate and collar (W1), kg
2. Weight of mould + compacted soil (W2), kg
3. Weight of compacted soil (W), gm
4. Wet density (γ)=w/v, g/cm3
5. Container
6. Weight of container (W3), gm
7. Weight of container + wet soil (W4), gm
8. Weight of container + dry soil (W5), gm
9. Water content (Wc)=(Ww)/(Wd)=(W4-W5)/(W5-W3)
10. Average Water content, Wc=(Wc1+Wc2+Wc3+Wc4)/4
11. Dry density, γdry = γ/(1+wc), g/cm3

Result:

Optimum moisture content (OMC) = ______________%

Maximum dry density (γmax )gms/cm3 = ______________%.

Verification/ Validation:

The peak point of the compaction curve - The peak point of the compaction curve is the point with the maximum dry density dry density. Corresponding to the maximum dry density ρdmax is a water content known as the optimum water content.The optimum water content is the water content that results in the greatest density for a specified compactive effort. Compacting at water contents higher than the optimum. water content results in a relatively dispersed soil structure (parallel particle orientations) that is weaker , more ductile, less pervious, softer, more susceptible to shrinking, and less susceptible to swelling than soil compacted dry of optimum to the same density.

Zero air voids curve: The curve represents the fully saturated condition (S = 100 %). (It cannot be reached by compact ion)

Conclusion:

The maximum density of the soil is ______ with an OMC of _______. This indicates, after w%, any additional water addition, there is no gain in strength of soil.

Viva Questions:

  1. What is the difference between standard proctor test and modified proctor test ?
  2. What is relative density of soil ?
  3. What is voids ratio? What is zero air voids line ?
  4. What is the practical implication of conducting standard proctor test ?
  5. How to determine OMC of soil? Explain.
  6. How is compaction different from consolidation ?
  7. Did you watch any civil engineering construction compaction is carried out? Explain.
  8. Is there any other method other than standard proctor test to determine maximum density ?

Determination of maximum dry density and optimum moisture content.

Aim:

To determine the optimum content and maximum dry density of a soil sample by standard proctor test.

Specification:

The experiment is conducted as per IS 2720-7(1980).

Equipments Required:

  • Proctor mould having a capacity of 1000cc with an internal diameter of 100mm and effective height of 127.3mm. The mould shall have a detachable collar assembly and detachable base plate.
  • Rammer: A mechanical operated metal rammer of weight of 2.6Kg , drop of 310mm. The rammer shall be equipped with a suitable arrangement to control the height of drop to free fall.
  • Sample extruder.
  • Balance of 15Kg capacity.
  • Sensitive balance.
  • Straight edge.
  • Graduate cylinder.
  • Mixing tools such as mixing pan, spoon, trowel, and spatula.

Theory:

Compaction is the application of mechanical energy to a soil so as to rearrange its particles and reduce the void ratio. It is applied to improve the properties of an existing soil or in the process of placing fill such as in the construction of embankments, road bases, runways, earth dams, and reinforced earth walls. Compaction is also used to prepare a level surface during construction of buildings. There is usually no change in the water content and in the size of the individual soil particles.

The objectives of compaction are:

  1. To increase soil shear strength and therefore its bearing capacity.
  2. To reduce subsequent settlement under working loads.
  3. To reduce soil permeability making it more difficult for water to flow through To assess the degree of compaction, it is necessary to use the dry unit weight, which is an indicator of compactness of solid soil particles in a given volume. The laboratory testing is meant to establish the maximum dry density that can be attained for a given soil with a standard amount of compactive effort.

To assess the degree of compaction, it is necessary to use the dry unit weight, which is an indicator of compactness of solid soil particles in a given volume. The laboratory testing is meant to establish the maximum dry density that can be attained for a given soil with a standard amount of compactive effort.

Precautions:

  • Thoroughly breakup the sample by running it through the screen before compacting it in the mould.
  • Pound within a moisture range from optimum to 4 percent below optimum. The closer to optimum the moisture content is, the more accurate the test will be.
  • Make sure the clamp on each mold section is tight.
  • Make sure the wing nuts on the base plate are secured with equal tension.
  • Place the mould on a solid block that is supported on firm soil or pavement.
  • Hold the rammer vertically so that it will fall freely.
  • Drop the 25 kg rammer weight freely
  • Use exactly 25 blows on each layer.
  • Place 3 equal layers in the mold

Procedure:

  1. Take a representative oven-dried sample, approximately 3Kg in the given pan. Thoroughly mix sample with sufficient water to dampen it to approximately four to six percentage below optimum moisture content.
  2. Weigh the proctor mould with base plate (W1). Fix the collar and base plate. Place the soil in the proctor mould and compact it in three layers giving 25 blows per layer with the 2.6 Kg rammer falling through a height of 310mm.
  3. Remove the collar, trim the compacted soil evenly with the top of the mould by means of straight edge and weigh.
  4. Divide the weight of the compacted specimen and record the result as the wet weight (γwet )gms/ cm3 of the compacted soil.
  5. Remove the sample from the mould and slice vertically through and obtain a small sample for moisture determination.
  6. Thoroughly break up the remainder of the material and add water in sufficient amounts to increase the moisture content of the soil sample by one or two percentage. Finally, repeat the above procedure for each increment of water added.
  7. Plot a graph between water content (w) and maximum dry density (γdry )gms/cm3 which exhibits optimum moisture content (OMC).
  8. Continue this series of determination until there is either a decrease or no change in the wet unit weight of the compacted soil.

Observation:

Height of mould ( H ) = mm.

Diameter mould ( d ) = mm.

Volume of mould (V) =(πd2)/4 x H= cm3.

Table: Weight of Soil for varying water content

Serial No. Details Test No.1 Test No.2 Test No.3 Test No.4
1. Weight of mould with base plate and collar (W1), kg 3.894 3.893 3.894 3.891
2. Weight of mould + compacted soil (W2), kg 5.268 6.062 6.014 5.950
3. Weight of compacted soil (W), gm
4. Wet density (γ)=w/v, g/cm3
5. Container 4 15 11 23
6. Weight of container (W3), gm 26 18 18 26
7. Weight of container + wet soil (W4), gm 46 34 38 46
8. Weight of container + dry soil (W5), gm 44 32 36 44
9. Water content (Wc)=(Ww)/(Wd)=(W4-W5)/(W5-W3)
10. Average Water content, Wc=(Wc1+Wc2+Wc3+Wc4)/4
11. Dry density, γdry = γ/(1+wc), g/cm3



Result:

Optimum moisture content (OMC) = % .

Maximum dry density (γmax ) = gms/cm3 .

Verification/ Validation:

The peak point of the compaction curve - The peak point of the compaction curve is the point with the maximum dry density dry density. Corresponding to the maximum dry density ρdmax is a water content known as the optimum water content.The optimum water content is the water content that results in the greatest density for a specified compactive effort. Compacting at water contents higher than the optimum. water content results in a relatively dispersed soil structure (parallel particle orientations) that is weaker , more ductile, less pervious, softer, more susceptible to shrinking, and less susceptible to swelling than soil compacted dry of optimum to the same density.

Zero air voids curve: The curve represents the fully saturated condition (S = 100 %). (It cannot be reached by compact ion)

Conclusion:

The maximum density of the soil is with an OMC of . This indicates, after w%, any additional water addition, there is no gain in strength of soil.

1. First video

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Websites and blog

Click on the link below to study about standard proctor test.

1. First blog

2. Second blog

3. Third blog

Refrence

1. Venkataramaiah, C. (2018). Geotechnical Engineering (6th ed.). New Age International Publishers Pvt Ltd.

2. Punmia, B.C( 2017)Soil mechanics and foundations(17th ed.).Laxmi publications Pvt Ltd.

3. Gopal R, Rao, A, S, R( 2016)Basic and applied Soil mechanics(3rd ed.).New Age International Publishers Pvt Ltd.

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