Determination of maximum dry density and optimum moisture content of soil using heavy compaction according to IS: 2720 (Part 8) - 1983.

Apparatus Required:

1. Cylindrical metal mould - it should be 100 mm diameter and 1000cc volume or 150mm diameter and 2250cc volume corresponding to IS: 10074 - 1982

2. Balances - one of 10 kg capacity, sensitive to 1 g and hence another 200 g capacity, sensitive to 0.01 g.

3. Oven - Thermostatically controlled with an indoor non-corrosive material to take care of temperatures between 105 and 110.

4. Steel straight edge - 30 cm long

5. IS Size - 4.75 mm, 19 mm and 37.5 mm

cylindrical mould

Sample Preparation:

A representative portion of the air-dried soil material, which is sufficient to supply about 6 kg of material to pass through a 19 mm IS sieve (the soil is not vulnerable to crushing during condensation) or through a 19 mm IS sieve about 15 kg of material passing through (susceptible to crushing during condensation), must be taken. This part must be sieved through a 19 mm IS sieve and therefore the coarse fraction is rejected after the proportion of the entire sample.

The aggregation of particles must be broken down in the order that if the sample was sieved through a 4.75 mm IS Sieve, only individual particles would be retained.


A) Soil not susceptible to crushing during compaction  or Soil is not weak during compaction -

i) A 5 kg sample of air-dried soil passing through a 19 mm IS sieve should be taken. The sample should be thoroughly mixed with the appropriate amount of water.

Soil type (for sandy and gravel soils - 3 to 5 % and for cohesive soils - 12 to 16% below the plastic limit). The soil sample should be stored for a minimum period of 16hrs within the sealed container.

ii) A 1000cc capacity mould should be attached to the base plate, weighing 1g (W1) to the nearest. The mould should be placed on a concrete base, like a concrete floor or plinth and therefore moist soil should be deposited and compacted in the mould, with extension fixed, in five layers of approximately equal mass, each layer being given 25 blows.

The 4.9 kg rammer fell from a height of 450 mm from the soil. Blows should be distributed evenly over the surface of each layer. Amount of soil used should be sufficient to fill the mould,leaving less than about 6 mm when the extension is removed. The extension must be removed and therefore compacted soil must be carefully sealed through the straight edge to the highest level of mould. The mould and soil is weighed to the nearest gram (W2).

iii) Compact soil samples should be removed from the mould and placed on a blending tray. The representative sample of the specimen’s water content  should be determined as well.

iv) The remaining soil sample should be rubbed and sliced ​​through a 19 mm IS sieve, then mixed with the remaining original sample. Appropriate increments of water should be added sequentially and mixed into the sample, and therefore the operations performed above (ii) to (iv) should be repeated for each increment of added water. The total number of determinations made must be a minimum of five and therefore the moisture content must be such an optimum moisture at which the maximum dry density lies within the range.

B) Soil susceptible to crushing during compaction  or Soil during compaction of soil -

Five or more 2.5 kg samples of air-dried soil passing through a 19 mm IS sieve should be taken. Samples must be mixed with varying amounts of water in each well and stored during a seal container as described in (para A)(i), above.

Follow the operations given in para A  (ii) to (iv), above.

C) Compaction in large size mould -

To deposit soil containing coarse material up to 37.5 mm size, a 2250cc mould should be used. A specimen weighing approximately 30 kg passing through the 37.5 mm IS Sieves should be employed for testing. The soil is compacted into five layers, each layer is given 55 blows of the 4.9 kg rammer. The remainder of the procedure is similar to Para (A) or( B) above.


The bulk density γ in g/cc of each compacted sample should be calculated from the equation

γ = (W2- W1) / V

Where, V = volume in the cc of the mould.

Dry density γd in g/cc = 100γ / (100+ w)

The dry density γd, obtained during a series of determination, should be plotted against the corresponding moisture content, w. A smooth curve must be drawn through the resulting points and hence the position of the maximum on the curve must be determined. A sample graph is shown below:

The dry density in g/cc corresponding to the maximum point on the moisture content / dry density curve

The dry density in g/cc corresponding to the maximum point on the moisture content / dry density curve should be reported nearest to 0.01 as the maximum dry density.

The percent moisture content corresponding to the maximum dry density on the moisture content / dry density curve should be reported as the optimal moisture content and quoted for the nearest 0.2 for values below 5%, 5 to 10 percent,to values closest to 0.5. Nearest whole number for values greater than 10 percent.


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For Testing:

Slump cone test, Silt content, Water absorption, Bulking of sand
Compaction factor test of concrete
Los Angeles Abrasion test on Aggregates

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