Compaction test of soil is also additionally called as Proctor’s test. It is normally undertaken to understand compaction properties of varied soils with alteration in moisture proportion.
For assessment of the compaction properties of a soil sample by proctor’s test
Theory
Compaction refers to the procedure of densification of soil by plummeting air voids. The extent of compaction of a specified soil is weighed in basis of its dry density. The dry density is greatest at the optimal water proportion. A curve is drawn between the water proportion and the dry density to acquire the maximum dry density and the best suitable water proportion.
Dry density of soil:
Where M = total mass of the soil,
V= volume of soil,
w= water content.
Equipment for compaction test of soil (proctor’s test):
- Oven
- Desiccator
- Weighing balance, accuracy 1g.
- Large mixing pan
- Rammer, mass 2.6 kg.
- Detachable base plate.
- Collar, 60mm high.
- IS sieve, 4.75 mm.
- Straight edge.
- Spatula
- Graduated jar
- Mixing tools, spoons, trowels, etc.
Process for the Compaction Test of Soil
1. First of all, take approximately 20kg of air-dried soil. Filter it through 20mm and 4.7mm sieve.
2. Compute the amount recollected on 20mm sieve and 4.75mm sieve, and the percentage passing through the 4.75mm sieve.
3. In those case where the percentage recollected on 4.75mm sieve is higher than 20, utilize the big mould of 150mm diameter. In those case, where the percentage is lower than 20%, the normal mould of 100mm diameter could be utilized. The following process is utilized for the standard mould.
4. Blend the soil recollected on 4.75mm sieve and that filtering through 4.75mm sieve in extents assessed in step (2) to attain approximately 16 to 18 kg of soil sample.
5.Thoroughly clean and dry the mould and the base plate. Grease them mildly.
6. Measure the weight of the mould with the base plate to the closest 1 gram.
7. Now take approximately 16 – 18 kg of soil sample. Put some water to it to bring the water proportion to about 4% in case the soil is sandy and to approximately 8% if the soil is clayey.
8. Transform the soil in an air-tight vessel for approximately 18 to 20 hours for maturing. Blend the soil methodically. Split the processed soil into 6 to 8 parts.
9. Fix the collar to the mould. Put the mould on a solid foundation.
10. Now take approximately 2.5kg of the processed soil, and therefore keep it in the mould in 3 uniform levels. Now take approximately one-third the proportion first, and compress it by delivering 25 blows of the rammer. The blows have to be evenly dispersed over the surface of every level.
The apex surface of the original layer has to be scratched with spatula prior to positioning the second layer. The second layer also has to be compressed by 25 blows of rammer. Similarly, keep the third layer and compact it as well.
The quantity of the soil utilized has to be just adequate to fill the mould and leaving approximately 5 mm beyond the top of the mould to be struck off when the collar is detached.
11. Eliminate the collar and trim off the additional soil protruding ahead of the mould with help of a straight edge.
12. Thoroughly clean the base plate and the mould from exterior part. Measure the weight of it to the closest gram.
13. Now detach the soil from the mould. The soil can additionally be ejected out.
14. Take the soil specimens the water proportion determination from the crest, middle and base segments. Compute the water content.
15. Augment approximately 3% of the water to a fresh content of the processed soil, and undertake the steps 10 to 14 repeatedly.
Fig: Standard Proctor Test (Compaction Test)
Data sheet for compaction test
Diameter of the mould =
Height of mould =
Volume of the mould, V=
Specific gravity of solids, G=
| Sl. No.
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Observations and Calculations
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Determination No.
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| 1
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2
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3
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| Observation
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| 1 | Mass of empty mould with base plate | |||
| 2 | Mass of mould, compacted soil and base plate | |||
| Calculations
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| 3 | Mass of compacted soil M = (2) – (1) | |||
| 4 | Bulk Density  |
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| 5 | Water content, w | |||
| 6 | Dry density  |
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| 7 | Void ratio  |
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| 8 | Dry density at 100% saturation (theoretical)
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| 9 | Degree of saturation  |
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Plot a curve between w as abscissa and 
as ordinate.
Result of Soil Compaction Test
Maximum dry density (from plot) =
Optimum water content (from plot) =