17-01-2014, 03:11 PM
TESTS ON BLANKET MATERIAL
AIM
To determine the particle size distribution of blanket material as
per IRS: GE - 3, July 2003.
PRINCIPLE
i) An oven-dried sample of known weight is washed in the
prescribed manner and the decanted wash water containing
suspended and dissolved matter is passed through 75μm IS
Sieve. The percentage reduction in weight of the original
material by washing is then reported as percentage fines in
the blanket material.
ii) An oven-dried sample of known weight is separated through
a set of IS Sieves of progressively smaller opening for
obtaining the percentage of the material passing through
each sieve and determining the particle size distribution.
APPARATUS
i) Balance, readable and accurate to 0.1g for fine particles and
to 0.5g for coarse fraction or to 0.2% of the test load,
whichever is greater
ii) IS Sieves of sizes - 40mm, 20mm, 10mm, 4.75mm, 2mm,
600μm, 425μm, 212μm, 75μm and bottom pan
iii) Thermostatically controlled oven of appropriate size to
o
maintain the temperature inside between 105 and 110 C,
having an interior of non-corroding material
iv) Mechanical sieve shaker
v) Tray - two or more of 30cm x 20cm x 10cm
vi) Wire brushes/sieve brushes
PROCEDURE
i)
Dry the test sample to a constant weight in a
thermostatically controlled oven at a temperature of 105 to
o
110 C and weigh it to the nearest 0.5g or 0.1% of the weight
of the sample.
Note: If large quantity of particle size greater than 4.75mm
is present, it may be separated to avoid overloading of
individual sieves by sieving, using 4.75mm sieve. Material
retained on the 4.75mm sieve is kept separately.
ii) After drying and weighing, place the test sample in the
container and soak it in water. The soaking of soil should be
continued for 10 to 12hrs. No dispersing agent or any other
substance should be added to the water.
iii) Agitate the sample with sufficient vigour to result in complete
separation of all particles finer than the 75μm IS Sieve, from
the coarser particles and bring the fine material into
suspension.
iv) The sample is washed through 4.75mm IS Sieve and 75μm
IS Sieve with water till substantially clean water comes out.
Material retained on sieves should be oven-dried at 105 to
o
110 C for 24hrs. The material retained on each sieve is
weighed to the nearest 0.1g or 0.1% of the original weight of
the sample, whichever is greater.
REPORTING OF RESULTS
i) Report percentage to the nearest whole number and the
percentage of material finer than 75μm sieve got by washing
to the nearest 0.1%.
ii) A particle size distribution curve should be drawn on semi-
log graph plotting size on the log scale against percentage
finer than the corresponding size on the ordinary scale (see
page 12).