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an optimum level which if exceeded dry unit weight decreases. It can be attributed to the fact that
water occupies spaces meant for soil particles. Optimum moisture content is the amount of
moisture content which translates to a maximum dry unit. In 1993 Proctor developed a
compaction test procedure applicable in the laboratory which can be used in determining
maximum dry unit weight during compaction of soil. The results from this laboratory procedure
can be used in field compaction. Proctor named this procedure standard Proctor compaction.
Some of the equipment required for this experiment include compaction mold, U.S No. 4
sieve, standard Proctor hammer weighing 24.4N, balance sensitive to 0.01lb, balance sensitive to
0.1g, larger flat pan, jack, steel straightedge, moisture can, drying oven, plastic squeeze bottle
with water.
For this experimentation, the following process should be followed. Collect a small
sample of the soil from the field or job site. Sieve the soil using 4.75mm sieve. Empty the
Proctor mold and weigh the base plate and collar. Also, weigh the empty containers. Thoroughly
mix the soil with around 9% of the total soil volume then divide the soil sample into three parts.
Using one of the three divisions, place it in the mold and compact it. Uniformly distribute
25blows on the surface and ensure that the hammer freely falls and there is no obstruction due to
the soil in the tube. Use the second division and later the third division. When compaction is
complete, remove the attached collar and use the straightedge to trim the compacted soil creating
a uniform compaction on the top of the mold. Take a small amount of soil from the upper side of
the mold and place in a container and weigh the soil sample. Take a small amount of soil from
the bottom side of the mold and weigh. Weigh the container without the soil samples then place
both containers in the oven to determine moisture content. To determine unit weight, divide the
weight of compacted soil with the volume of the mold.
