Proctor Compaction Test
for Maximum Dry Density
What Is Compaction?


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Compaction is the process of increasing the bulk
density of a soil or aggregate by driving out air.
For any soil, at a given compactive effort, the
density obtained depends on the moisture
content.
For any soil, an “optimum water content” exists
at which it will achieve it’s maximum density.
Soils are compacted for the
following reasons:
1.
2.
3.
4.
To increase strength and stability
To decrease permeability
To enhance resistance to erosion
Decrease compressibility under load and
minimize settlement
Common Equipment
Shown:
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Sheepsfoot
Padfoot
Vibratory Roller
Grid Roller
Dynamic Compaction:
Profile of Overlap
Definition: Maximum Dry Density
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
The peak dry unit weight is called the
"maximum dry density”.
The Optimum Water Content, wopt, is the
water content at the soil’s maximum dry
density.
Achieving Maximum Compaction
In The Field
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Proctor Compaction Test determines the optimum water
content and maximum dry density of for a soil.

A required range for moisture is often specified by the
engineer:
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Ie, 3% below and 2% above optimum.

For example, if optimum water content is 16%, the
acceptable range would be from 13% to 18%.
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Percent compaction is also specified:

Meaning “required percentage of max dry density”
% Compaction = ρdry field /ρdry max
Dry Density Curve: Proctor Test
How Does A Contractor Modify
Compaction in the Field?
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Adjust Water Content
More Passes
Thinner Lifts
Bigger Rollers
How Do We Determine
Actual Field Density?

Sand Cone Test
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Nuclear Densometer
Getting Back To The Proctor
Compaction Test
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Test developed to help
specify levels (%)
compaction (1933).
Ralph R. Proctor first
defined this standard
compaction test in
Engineering News Record
Proctor Compaction Procedure
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Soil is air dried, pulverized
& passed thru #4 sieve.
Separated into 4 to 6 samples.
Adjust the water content of each sample by adding
water.
Proctor Compaction Procedure
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
Using the proctor mould (1/30th cubic foot)
place & compact soil in 3 layers.
Each layer should receive 25 drops of the
compaction hammer.
Proctor Compaction Procedure

After the last layer, use a straight edge to
trim the excess soil leveling to the top of
the mould.
Proctor Compaction Procedure
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Determine the weight of the mould with
the compacted moist soil.
Extrude from mould and collect a sample
for water content determination.
Repeat for each sample over a range of
moisture contents.
Proctor Compaction Procedure

After collecting all
pertinent weights,
calculate dry density
and plot vs. water
content
Typical Proctor Data
1
2
3
4
5
8
9
Mold (lbs)
Mold + Wet
Soil (lbs)
Moist Soil (lbs)
Moisture
Content
Dry Unit Wt.
9.31
13.23
3.92
117.60
61.00
273.50
249.70
0.13
104.43
9.20
13.60
4.40
132.00
61.00
280.00
249.20
0.16
113.44
9.31
13.52
4.21
126.30
61.00
242.90
214.90
0.18
106.86
9.30
13.34
4.04
121.20
61.00
306.70
265.60
0.20
100.93
9.20
13.25
4.05
121.50
61.00
222.60
190.20
0.25
97.14
9.31
13.16
3.85
115.50
61.00
212.20
178.10
0.29
89.45
Moist Unit Wt. Mass of Can
(pcf)
(g)
(Line 3)/(1/30)
6
7
Mass Can + Mass of Can +
Moist Soil (g)
Dry Soil
(Line 4)/(1+Line 8)
Graph from Proctor Data
Proctor Compaction Results
120
115
Dry Density (pcf)
110
105
100
95
90
85
80
0.00
0.10
0.20
Water Content
0.30
0.40
Achieving Maximum
Compaction
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For any job requiring fill/compaction the engineer will
specify the compaction requirements:
ODOT Roadway Embankment Requirements:
Maximum Laboratory
Dry Weight
[lb/ft3 ]
90 to 104.9
Minimum Compaction
Requirements in Percent of
Laboratory Maximum
102
105 to 119.9
100
120 and higher
98
Achieving Maximum
Compaction
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Since the maximum dry density is material
specific,
AND
Since material being hauled in may
change from truck to truck,
It is necessary to verify the maximum dry
density number for the material being
placed.
One-Point Proctor
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Thus, the one-point proctor is used to
verify the maximum dry density of soils in
the field.
One proctor test is done to determine the
wet density vs. moisture content.
Then a “family of curves” is used to
determine the maximum dry density.
ODOT Family of Curves
Percent Compaction

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Then, comparing the maximum dry
density to the ACTUAL density being
achieved (nuclear densometer), we can
calculate % compaction.
% Compaction = ρdry field /ρdry max