For determination of the relation between the water content and the dry density of soils using light compaction.
IS: 2720(Part 7)-1980- Methods of test for soils: Determination of water content-dry density relation using light compaction.
Equipments & Apparatus
- Cylindrical mould & accessories [volume = 1000cm3]
- Rammer [2.6 kg]
- Balance [1g accuracy]
- Sieves [19mm]
- Mixing tray
- Graduated cylinder [500 ml capacity]
- Metal container
Obtain a sufficient quantity (10 kg) of air-dried soil and pulverize it. Take about 5 kg of soil passing through 19mm sieve in a mixing tray.
- 5 Kg. of soil is taken and the water is added to it to bring its moisture content to about 4 % in coarse grained soils and 8% in case of fine grained soils with the help of graduated cylinder
- The mould with base plate attached is weighed to the nearest 1 gm (M1). The extension collar is to be attached with the mould.
- Then the moist soil in the mould is compacted in three equal layers, each layer being given 25 blows from the 2.6 Kg rammer dropped from a height of 310 mm. above the soil.
- The extension is removed and the compacted soil is leveled off carefully to the top of the mould by means of a straight edge.
- Then the mould and soil is weighed to the nearest 1 gm. (M2).
- The soil is removed from the mould and a representative soil sample is obtained water content determination.
- Steps 3 to 6 are repeated after adding suitable amount of water to the soil in an increasing order.
Bulk density, gm in g/cm3 at each compacted specimen is calculated from the equation.
where Vm = volume of mould in cm3
The dry density, gd, in g/cm3, is calculated from the equation.
where w = moisture content of soil in percent.
The dry densities, gd obtained in a series of determinations are plotted against the corresponding moisture content. A smooth curve is then drawn through the resulting points and the position of the maximum on this curve is determined.
The maximum dry density in g/cm3 is to be reported to the nearest 0.01 and the optimum moisture content is to be reported to the nearest 0.5.
Safety & Precautions
- Use hand gloves & safety shoes while compacting.
- Adequate period (about 15 minutes for clayey soils and 56 minutes for coarse grained soils) is allowed after mixing the water and before compacting into the mould.
- The blows should be uniformly distributed over the surface of each layer.