Determination of maximum dry density and optimum moisture content of soil by modified proctor test (Heavy compaction test).

**Test standard :** IS 2720-Part 8: 1983

**Test Apparatus **

- Cylindrical mould of 150mm diameter of 2250 cm
^{3}or 100mm diameter of 1000 cm^{3}capacity with base plate and collar. - Metal rammer of 4.9kg weight with an height of fall of 45 cm.
- Weighing balances of 1gm and 0.01gm capacities.
- Thermostatically controlled hot air oven to maintain temperature between 105 °C -110 °C .
- Air tight container for determining the moisture content.
- IS Sieve 37.5mm or 19mm sizes.
- Tray for mixing of soil, trowel, spatula, measuring jar.

**Test Procedure**

**Compaction in 2250 cm ^{3} Volume mould :**

- First note the empty weight of the cylindrical mould of 2250 cm
^{3}capacity. - Place the mould on a solid base, such as concrete floor or plinth, than take an air-dried / oven dried sample of 30kg passing 37.5mm sieve.
- Divide it into five equal parts (approximately) a minimum wt. of 5500 gms by quartering method.
- Take one part of the above sample and add a known percentage of water by the weight of the soil. Once again make it into five equal parts.
- Place one part into the mould fitted with collar and compact the soil with the metal hammer by distributing the 55 blows equally on the surface of the soil. Continue this process till the fourth layer. Make an impression on the fourth layer of the compacted soil to a depth of 25 mm, so that the next layer will plug into this and avoid separation of the top layer form the previous while removing the collar. Add fifth layer and compact it with metal hammer by giving 55 blows. Remove the collar and also remove the excess soil up-to the level exactly equal to the cylindrical mould by using trowel or spatula.
- Note the weight of the sample with the mould to the nearest 1gm. De-mould the soil form the mould and take a representative sample from the middle, fill it in the airtight container for moisture determination.
- Note down the container number, the weight of the container and the sample including container to the nearest 0.01gm and place the container in a thermostatically controlled oven for 24 hrs at 105 °C to 110 °C.
- Repeat same procedure, by taking each other four parts of soil by adding water of equal increments and noting down the weight of compacted soil with mould and container for the moisture determination for each increment of the water.
- Report the same in the format and calculate wet density, moisture content and dry densities.

**Compaction in 1000 cm ^{3} Volume mould :**

Note the empty weight of the cylindrical mould of 1000 cm^{3} capacity to the nearest 1gm.

Place the mould on a solid base, such as concrete floor or plinth, than take an air-dried / oven dried sample of 5kg passing 19mm sieve.

Make it into to five equal parts by quartering method. Take one part of the above sample and add a known percentage of water by the weight of the soil. Once again make it into five equal parts, and place one part into the mould fitted with collar. Compact the soil in five layers with the metal hammer by distributing the 25 blows equally on the surface of the soil. The test procedure is same as given above.

**Calculation**

Plot a graph with the above values for moisture content Vs dry density, draw an average line passing through each point on the graph with French curves.

Report MDD & OMC from the graph, which is the peak point of the curve.

**Example of Maximum dry density of soil**

Read more :

- Determination of Specific gravity of soil
- Determine the liquid limit and plasticity index of soil by casagrande apparatus
- Shrinkage limit test of soil | Laboratory Soil testing
- Specific gravity test of soil, IS 2720-Part 3

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