The Standard & Modified Proctor Density Tests

mixing tools
oven for drying moisture content samples.
PROCEDURE (Modified Test):
1. Take 6 000 g of sand and mix with 600 g of bentonite or if pre-mixed soil is available about 6½
kg.
2. Add about 7% water to the sample or as given by the instructor and mix thoroughly until all the
water is uniformly absorbed.
3. Weigh the empty mould without the collar or base and record its mass.
4. With the collar attached to the mould, compact a specimen in five equal layers to get a total
compacted depth of about 130 mm with 55 uniformly distributed blows of the rammer per layer
of the specimen. During compaction the mould should rest directly on the concrete floor of the
lab.
5. Remove the collar from the mould and strike off the soil with the straight edge. Weigh the mould
and soil and record their mass. Subtract the mass of the mould from the specimen and multiply
this mass by 471 and record the result as the wet density in kg per cubic metre of the compacted
specimen.
6. Remove the soil from the mould. Obtain a moisture content sample from the centre of the
specimen, weigh and place in the oven to dry. The moisture content sample should weigh
approximately 100 g.
7. Break up the sample and re-mix with the material that was not used in the test and add
approximately to 2% more water. Re-mix again and repeat the compaction procedure and obtain
the moisture content of the sample. This procedure is repeated again and again until, for two
trials, there is a decrease in the wet density of the compacted soil. A minimum of 5 points will be
required to plot the moisture density curve.
CALCULATIONS (Modified Test):
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Wet density The volume of the 6 inch mould is or (0.002124) m
471
where
ρ = M x 471
ρ = wet density in kg/m 3
M = mass of wet soil contained in the mould in kg (does not include the mould)
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