IS light compaction test
Objective:
To determine the compaction characteristics of a soil sample using IS
light
compaction test.
Theory:
Compaction is the process of packing soil particles closely together
by
mechanical means to increase its dry density.
There is an optimum amount of mixing water for a given soil and compaction
process,
which will give a maximum weight of soil per unit volume. This corresponds
to the
maximum dry density of the soil.
Apparatus
1. Standard Proctor mould with base plate and collar (should conform to
IS
10074:1982).
2. Standard Proctor hammer
3. G.I. trays (600×500×80mm deep)
4. Weighing balance of 1g accuracy to weigh up to 10kg
5. Weighing balance of 0.01g accuracy to weigh moisture cans
6. Trowels
7. Measuring cylinder
8. Moisture cans
9. Extractor jack
10. Scraper (straight edge)
11. Grease or oil
Procedure
1. Note the dimensions of mould, collar and the base plate.
2. Apply a thin film of grease on inside of the mould.
3. Take the empty weight of the mould (without collar and base
plate).
4. Fix the mould to the base plate with the help of wing nuts, place collar
on the mould.
5. Take about 3000g of deaired soil passing through sieve size 4.75 mm in
tray.
6. Add about 4 % water (approximately 120ml) to the soil and mix
thoroughly with
trowel and cover it with moist cloth.
7. To determine the Proctor density, place the soil in the mould in 3
layers of 50 mm
thick, each in a loose state and give 25 blows to each layer using
standard hammer.
Scrap the top surface of the compacted layer before placing the next
layer of a soil.
Ensure that after compaction of the third layer, the level of compacted
soil slightly
above the top of the mould (usually within 5mm).
8. Remove the collar trim the soil with a straight edge, disconnect the
mould from base
plate and weigh it.
9. Take two samples from top and bottom respectively of the mould for
water content
determination.
10. Extrude the compacted soil from the mould and break it in to original
size. Add
another 3-4% of water and repeat step 7 to 9.
11. Continue the operations until a decrease in the weight of a soil is
observed for at least
two successive readings.
12. Draw a plot of water content v/s. dry density. Determine the maximum
dry density
and optimum moisture content corresponding to the standard proctor
compaction.
13. On the same graph (in step 12), plot constant degree of saturation
lines for 100%,
90%, 80% degrees of saturation. Calculate the degree of saturation
corresponding to
the maximum dry density.
