PART 8 DETERMINATION OF WATER CONTENT-DRY DENSITY RELATION USING HEAVY COMPACTION

SCOPE
1.1 This standard ( Part 8) lays down the method for the determination
of the relation between the water content and the dry density of soils
using heavy compaction.
2. TERMINOLOGY
2.1 For the purpose of this standard, the definitions given in IS : 2809-
19727 shall apply.
3. APPARATUS
3.1 Cylindrical Metal Mould - It shall be either of 100 mm diameter
and I 000 cm3 volume or 150 mm diameter, and 2 250 cm3 volume
and shall conform to IS : 10074-1982:.
3.2 Sample Extruder ( Optior.al) - It consists of a jack, lever frame
or other device adopted for the purpose of extruding compacted
specimens from the mould.
3.3 Balances - One of 10 kg capacity sensitive to 1 g, and other of 200 g
capacity and sensitive to 0’01 g.
3.4 Oven -Thermostatically controlled, with interior of non-corroding
material to maintain temperature between 105% and 110°C.
3.5 Container - Any suitable non-corrodible airtight container to
determine the water content for tests conducted in the laboratory.
3.6 Steel Straightedge - A steel straightedge about 30 cm in length
and having one bevelled edge.
3.7 Sieve - 4*75-mm, 19-mm and. 37.5 mm IS sieves conforming to
IS: 460 ( Part I )-1978s.
*Rllles for roundirlg off numerical values ( revised).
~Glossary ofterms and symbols relating to soil engineering (jirst revision ).
;Specification for compaction mould assembly for light and heavy compaction of
soils.
$Specification for test sieves: Part 1 Wire cloth test sieves ( srcond revirion ).
4
IS : 2720 ( Part 8) - 1983
3.8 Mixing Tools - Miscellaneous tools, such as tray or pan, spoon,
trowel and spatula, or a. suitable mechanical device for thoroughly
mixing the sample of soil with additions of water.
3.9 Metal ‘Rammer - Heavy compaction rammer conforming to
IS : 9 189-1979*.
4. SOIL SPECIMEN
4.1 A representative portion of air-dried soil material and large enough
to provide about 6 kg of material passing a 19-mm IS sieve (for soils
not susceptible to crushing during compaction ), or about 15 kg of
material passing a 19 mm IS sieve ( for soils susceptible to crushing
during compaction ), shall be taken ( see Note ). This portion shall be
sieved on a 19 mm IS sieve and the coarse fraction rejected after its
proportion of the total sample has been recorded.
~NOTR -The soil should be considered susceptible to crushing during
comtxrction if the samole contains granular material of a soft nature. such as soft
lime‘ stone, sandstone, ‘etc , I which ii reduced in size by the action of the 4.9-kg
rammer. The procedure given in 5.2 for soils susceptible to crushing during
compaction can be applied to all soils if it is convenient to do so.
4.1.1 Aggregations of particles shall be broken down so that if the
sample was sieved on a 4.75-m IS sieve, only separated individual
particles would be retained.
5. PROCEDURE
5.1 Soil Not Susceptible to Crushing During Compaction ( see
Note under 4.1 ) - The procedure is as follows:
5.1.1 A 5-kg sample of air dried soil passing the 1%mm IS test sieve
shall be taken (see Note 1 ). The sample shall be mixed thoroughly
with a suitable amount of water depending on the soil type ( see Notes
2 and 3 ).
5.1.2 The mould, of 1 000 cm3 capacity with baseplate attached, shall
be weighed to the nearest 1 g ( m, ). The mould shall be placed on a
solid base, such as a concrete floor or plinth and the moist soil shall
be compacted into the mould, with the extension attached, in five
layers of approximately equal mass, each layer being given 25 blows
from the 4*9-kg rammer droped from a height of 450 mm above the
soil. The blows shall be distributed uniformly over the surface of each
layer. The operator shall ensure that the tube of the rammer is kept
clear of soil so that the rammer always falls freely. The amount of soil
*Specification for compaction rammer for soil testing.
5
IS : 2720 ( Part 3 ) - 1983
used shall be suficient to fill the mould, leaving not more than about
6 mm to be struck off when the extension is removed (see Note 4 ),
The extension shall be removed and the compacted soil shall be levelled
off carefully to the top of the mould by means of the straightedge. The
monld and soil shall then be weighed neaIest to 1 g ( ~2“ ).
5.1.3 The compacted soil specimen shall be removed from the mould
and placed on the mixing tray. The water content of a representative
sample of the specimen shall be determined as in IS : 2720 ( Par: 2 )-
1973*.
5.1.4 The remainder of the soil specimen shall be broken up, rubbed
through the 19-mm IS test sieve, and then mixed with the remainder
of the original sample. Suitable increments of water ( SCE Note 5 ) shall be
added successively and mixed into the sample, and the above procedure
from operations 5.1.2 to 5.1.4 shall be repeated for each increment of
water added. The total number of determinations made shall be at
least five, and the moisture contents should be such that the optimum
moisture content, at which the maximum dry density occurs, is within
that range.
5.2 Soil Susceptible to Crushing During Compaction (see Note
under 4.1 ) - The procedure is as follows :
5.2.1 Five or more 2.5 kg samples of air-dried soil passing the 1%mm
IS sieve, shall be taken ( see Note 1 ). The samples shall each be mixed
thoroughly with different amounts of warer to give a suitable range of
moisture contents (see Notes 2 and 3 ). The range of moisture content,
at which the maximum dry density occurs, is within that range ( .W
Kate 5 ).
5.2.2 Each sample shall be treated as in 5.1.2.
5.2.3 Each specimen shall be treated as in 5.1.3.
5.2.4 The remainder of each soil specimen shall be discarded.
5.3 Compaction ilm Large Size Mould - For compacting soil
containing coarse material up to 37.5 mm size, the 2 250 cm3 mould
should be used. A sample weighing about 30 kg and passing the 37.5 mm
IS sieve is used for the test. Soil is compacted in fibe layers, each layer
being given 55 blows of the 4*9-kg rammer. The test of the procedure
is the same as in 5.1 or 5.2.
NOTE 1 - The removal of small amounts of stone ( up to 5 percent ) retained on
a 1%mm IS sieve will effect the density obtainable only by amounts comparable
l Sfcthods of test for soil : Part 2 Determination of water contcnr (scconri rsukion)
6
IS ,: 2720 ( Part 8 ) - 1983
with the experimental error involved in measuring the maximum dry density; The
exclusion of a large proporation of stone coarser than 19-mm may have a major
effect on the density obtained compared with that obtainable with soil as a whole,
and on the optimum moisture content. There is at present no generally accepted
method of test of calculation for dealing with this difficulty in comparing
laboratory compaction test results with densities obtained in the field. For soils
containing larger proportions of gravel, the use of a bigger mould ( 2250 ems ) will
avoid major errors.
NOTE 2-The amount of water to be mixed with air-dried soil at the
commencement of the test will vary with the type of soil under test. In general,
with sandy and gravelly soils a moisture content of 3 to 5 percent would be-suitable,
whiie with cohesive soils a moisture content about 12 to 16 percent below the plastic
limit of the soil should usually be suitable.
NWTE 3 - It is important that the water is mixed thoroughly and adequately
with the soil, since inadequate mixing gives rise to variable test results. This is
particularly important with cohesive souls when adding a substantial quantity of
water to the air-dried soil. With clays of high plasticity, or where hand mixing is
employed, it may be difficult to distribute the water uniformly through the air-dried
soil by mixing alone, and it may be necessary to store the mixed sample in a sealed
container for a minimum period of about 16 hours before continuing with the test,
NOTE 4.- It is necessary to control the total volume of soil compacted, since it
has been found that if the amount of soil struck off after removing the extension is
too great, the test results will be inaccurate.
NOTE 5 - The water added for each stage of the test should be such that a
range of moisture contents is obtained which includes the optimum moisture. In
general, increments of 1 to 2 percent are suitable for sandy and gravelly soils and
of 2 to 4 percent for cohesive soils. To increase the accuracy of the test it is often
advisable to reduce the increments of water in the region of the optimum moisture
content.
6. CALCULATIONS
6.1 Bulk Density -Bulk density, Y,, in g/ems of each compacted
specimen shall be calculated from the equation:
Trn L!!?+L?%
m
where
m, = mass in g of mould and base;
ml = mass in g of mould, base and soil; and
Vm = volume in cm3 of mould.
6.2 Dry Density - The dry density, Yd, in g/cm’, shall be calculated
from the equation :
where
w = moisture content of soil
7
in percent.
IS : 2720 ( Part 8 ) - 1983
6.3 The dry densities, Yd obtained in a series of determinations shall be
plotted against the corresponding moisture contents ZC. A smooth curve
shall be drawn through the resulting points and the position of the
maximum on this curve shall be determined.
7. REPORTING OF RESULTS
7.1 The experimental points and the smooth curve drawn through them
showing the relationship between moisture content and dry density shall
be reported.
7.2 The dry density in g/cm3 corresponding to the maximum point on
the moisture content/dry density curve shall be reported as the maximum
dry density to the nearest 0.01.
7.3 The percentage moisture content corresponding to the maximum
dry density on the moisture content,‘dry density curve shall be reported
as the optimum moisture content and quoted to the nearst O-2 for values
below 5 percent to the nearest 0.5 for values from 5 to 10 percent, and to
the nearest whole number for value exceeding 10 percent ( SPC Note
under 7.5 ).
7.4 The amount of stone retained on the 19-mm IS sieve shall be reported
to the nearest 1 percent.
7.5 The method of obtaining the result shall be stated, ( 4*9-kg rammer
method ). The procedure used shall also he stated that is single sample
or separate sample and the size of the mouid used.
NOTE -For~sorne highly permeable soils such as clean gravels, uniformily
graded and coarse cleen sands the results of the laboratory compaction test ( 4.9-
rammer method ) may provide only. a poor guidr tor specifications on !ield
compaction. The laboratory test often Indicates higher values of optimum moisture
content than would be desirable for field compaction and thr maximum dry density
is often much lower than the state of compaction, that can readily be obtained in the