Description
Proctor Compaction Test 1
Florida Institute of Technology
CVE 3021 Lab 4
Lab #4: Proctor Compaction Test
Objectives
The standard proctor compaction and modified proctor compaction tests will be employed to:
1. Determine the relationship between moisture content and the dry density of a soil for a
specified compactive effort
2. Ascertain the maximum dry unit weight (?dmax) and optimum moisture content (mopt) tests
of said sample of fine-grained uniformly graded sand soil
Introduction
The main references for the identified proctor tests to determine the ?dmax and mopt of the
soil sample are ASTM D 698 and ASTM 1557 respectively.
The standard proctor test utilizes the standard proctor mold which is 4.6 inches in depth,
and 4.0 inches in diameter. This results in a mold volume of 1/30 cubic feet. The standard hammer
weighs 5.5 pounds. The modified proctor?s mold size and volume are the same as the standard.
The modified hammer weighs 10 pounds. In each case, a drop of the hammer (one blow count per
each hammer drop) transfers a set amount of energy to the soil. As a result of the differing weights
of the hammer, the modified proctor transfers a greater amount of energy to the soil. This implies
that the soil compacted with the modified proctor has a higher maximum density than the soil
compacted under the standard proctor. Additionally, the optimum moisture content decreases with
the increased maximum dry unit density for the modified proctor test.
As the hammer is applied to the soil to compact it, mechanical energy is being transferred
and the soil particles arrange themselves such that the void ratio is reduced. There is need to
compact soils since this avoids issues of settlement in the soil subjected to live loads. As a result
the shear strength of the soil increases. Large water pressures are not allowed to build up in
compacted soils, therefore, liquefaction of the soil during certain natural disasters as earthquakes
can be mitigated. Further, since the reduction of void ratio is a consequence of compaction, the
soil then becomes best suited for projects requiring water-retention capabilities in the sense of not
allowing passage of water through the soil; an earth dam for example.
The pertinent materials and apparatus along with the procedures for the aforementioned
tests, follow. Note that the procedure in its entirety should be referenced in the ASTM Standards.
Only a summary follow.
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Proctor Compaction Test 2
Methodology1
Equipment
Molds, Manual rammer, Extruder, Balance, Drying oven, Mixing pan, Trowel, #4 sieve,
Moisture cans, Graduated cylinder, Straight Edge.
Procedure
1. Depending on the type of mold you are using obtain a sufficient quantity of air-dried soil in
large mixing pan. For the 4-inch mold take approximately 10 lbs, and for the 6-inch mold take
roughly 15 lbs. Pulverize the soil and run it through the # 4 sieve.
2. Determine the weight of the soil sample as well as the weight of the compaction mold with its
base (without the collar) by using the balance and record the weights.
3. Compute the amount of initial water to add by the following method:
a. Assume water content for the first test to be 8 percent.
b. Compute water to add from the following equation:
(???? ???? ?? ?????) ? 8
????? ?? ??? (?? ??) =
100
Where ?water to add? and the ?soil mass? are in grams. Remember that a gram of water is
equal to approximately one milliliter of water.
4. Measure out the water, add it to the soil, and then mix it thoroughly into the soil using the
trowel until the soil gets a uniform color (See Photos B and C).
1
Disclaimer: The methodology herein is based on Experiment 9 of Engineering Properties of Soils Based on
Laboratory Testing by Prof. Krishna Reddy, UIC. All credit is attributed to Prof. Krishna Reddy.
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Proctor Compaction Test 3
5. Assemble the compaction mold to the base, place some soil in the mold and compact the soil
in the number of equal layers specified by the type of compaction method employed (See
Photos D and E). The number of drops of the rammer per layer is also dependent upon the type
of mold used (See Table 1). The drops should be applied at a uniform rate not exceeding around
1.5 seconds per drop, and the rammer should provide uniform coverage of the specimen
surface. Try to avoid rebound of the rammer from the top of the guide sleeve.
6. The soil should completely fill the cylinder and the last compacted layer must extend slightly
above the collar joint. If the soil is below the collar joint at the completion of the drops, the
test point must be repeated. (Note: For the last layer, watch carefully, and add more soil after
about 10 drops if it appears that the soil will be compacted below the collar joint.)
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Proctor Compaction Test 4
7. Carefully remove the collar and trim off the compacted soil so that it is completely even with
the top of the mold using the trowel. Replace small bits of soil that may fall out during the
trimming process (See Photo F).
8. Weigh the compacted soil while it?s in the mold and to the base, and record the mass (See
Photo G). Determine the wet mass of the soil by subtracting the weight of the mold and base.
9. Remove the soil from the mold using a mechanical extruder (See Photo H) and take soil
moisture content samples from the top and bottom of the specimen (See Photo I). Fill the
moisture cans with soil and determine the water content.
10. Place the soil specimen in the large tray and break up the soil until it appears visually as if it
will pass through the # 4 sieve, add 2 percent more water based on the original sample mass,
and re-mix as in step 4. Repeat steps 5 through 9 until, based on wet mass, a peak value is
reached followed by two slightly lesser compacted soil masses.
The procedure outlined for the standard proctor test is the same for the modified proctor test
except for the hammer used for compaction and the number of intervals. The modified proctor
compaction test is based on ASTM Standard D1557. The mold size and volume are the same
as the standard. The modified hammer weighs 10 pounds. Again, four trials will be done as
with the standard proctor test. The second change is the quantity of intervals for each
compaction trial. The modified proctor compaction test includes five intervals and at each
interval 25 hammer blows must be applied to the soil in the mold.
Results ? See Data Sheet.
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Proctor Compaction Test 5
Analysis of results
1. Calculate the moisture content of each compacted soil specimen by using the average of the
two water contents.
2. Compute the wet density in grams per cm3 of the compacted soil sample by dividing the wet
mass by the volume of the mold used.
3. Compute the dry density using the wet density and the water content determined in step 1.
Use the following formula:
?
?? =
1+?
where: w = moisture content in percent divided by 100, and ? = wet density in grams per cm3.
4. Plot the dry density values on the y-axis and the moisture contents on the x-axis. Draw a
smooth curve connecting the plotted points.
5. On the same graph draw a curve of complete saturation or ?zero air voids curve?. The values
of dry density and corresponding moisture contents for plotting the curve can be computed
from the following equation:
?? 1
??
???? = ( – ) ? 100
??
?? =
?
1
?? ??
(100 – ? )
?
where:
?d = dry density of soil grams per cm3
Gs = specific gravity of the soil being tested (assume 2.70 if not given)
?w = density of water in grams per cm3 (approximately 1 g/cm3)
wsat = moisture content in percent for complete saturation.
6. Identify and report the optimum moisture content and the maximum dry density. Make sure
that you have recorded the method of compaction used (e.g., Standard Proctor, Method A) on
data sheet.
References
ASTM D698-12e2 Standard Test Methods for Laboratory Compaction Characteristics of Soil
Using Standard Effort (12 400 ft-lbf/ft3 (600 kN-m/m3)), ASTM International, West
Conshohocken, PA, 2012, https://doi.org/10.1520/D0698-12E02
ASTM D1557-12e1 Standard Test Methods for Laboratory Compaction Characteristics of Soil
Using Modified Effort (56,000 ft-lbf/ft3 (2,700 kN-m/m3)), ASTM International, West
Conshohocken, PA, 2012, https://doi-org.portal.lib.fit.edu/10.1520/D1557-12E01
Coduto, D. P., Yeung, M. R & Kitch, W. A. (2010). Geotechnical Engineering: Principles and
Practices.
Mamlouk, Michael S., and John P. Zaniewski. Materials for civil and construction engineers.
Pearson Higher Ed, 2011.
Reddy, K. (2002). Experiment 9 of Engineering Properties of Soils Based on Laboratory
Testing, UIC. (qtd. Engineering Properties of Soils. Tata McGraw-Hill Publishing
Company).
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Proctor Compaction Test 6
Florida Institute of Technology
CVE 3021 Data Sheet
Lab #4: Proctor Compaction Tests
Date Tested: _________________
Tested By: ____________________________________________________________________
Visual Classification of Soil: ______________________________________________________
______________________________________________________________________________
Standard Proctor Test
Standard Proctor Compaction Test
Test
1
2
3
Weight of Mold, W1 (lb)
Weight of Mold + Moist Soil, W2 (lb)
Weight of Moist Soil, W2 – W1 (lb)
Moist Unit Weight, ? (lb/ft3)
Moisture Can Number
Mass of Can, W3 (g)
Mass of Can + Moist Soil, W4 (g)
Mass of Can + Dry Soil, W5 (g)
Moisture Content, w (%)
Dry Unit Weight of Compaction, ?d (lb/ft3)
Table 1: Standard Proctor Compaction Test: Dry Unit Weight and Moisture Content
Sample Calculations
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4
Proctor Compaction Test 7
Modified Proctor Compaction Test
Modified Proctor Test
Test
1
2
3
Weight of Mold, W1 (lb)
Weight of Mold + Moist Soil, W2 (lb)
Weight of Moist Soil, W2 – W1 (lb)
Moist Unit Weight, ? (lb/ft3)
Moisture Can Number
Mass of Can W3 (g)
Mass of Can + Moist Soil, W4 (g)
Mass of Can + Dry Soil, W5 (g)
Moisture Content, w (%)
Dry Unit Weight of Compaction, ?d (lb/ft3)
Table 2: Modified Proctor Compaction Test: Dry Unit Weight and Moisture Content
Zero-Air-Void Unit Weight Determination
Specific Gravity of Soil Solids, Gs
Unit Weight of Water, ?w (lb/ft3)
Standard
Modified
Moisture Content
Zero Air Void Unit
Weight
Moisture Content
Zero Air Void
Unit Weight
w (%)
?zav (lb/ft3)
w (%)
?zav (lb/ft3)
Table 3: Zero-Air-Void (ZAV) Unit Weight Determination
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4
Proctor Compaction Test 8
Dry Unit Weight (pcf) vs. Moisture Content (%)
140
Dry Unit Weight, (pcf)
135
130
125
120
115
110
105
100
0
2
4
6
8
10
12
14
Moisture Content (%)
Standard Proctor
Modified Proctor
ZAV_Standard
Figure 1: Dry Unit Weight (pcf) vs. Moisture Content (%); Zero-Air-Void (ZAV) Curves
From Figure 1 the following may be had:
1. Standard Proctor Compaction Test:
a. Maximum Dry Unit Density =
b. Optimum Moisture Density =
2. Modified Proctor Compaction Test:
a. Maximum Dry Unit Density =
b. Optimum Moisture Density =
Sample Calculations:
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ZAV_Modified
16
18
Proctor Compaction Test 9
Lab Report Format and Guidelines
Section
Letter of
Transmittal
Introduction/
Description of
Soil Samples
Methodology/
Equipment
Analysis/
Results
Discussion
Description
?
?
?
?
Format
Lab performed, date, location
Description of tests/measurements preformed
Description of report contents
? Concluding statement
?
?
?
?
?
Conclusion
?
?
?
5
Include a picture and description of the equipment used to
perform this experiment. Label if necessary.
Briefly provide a list or paragraph of the steps performed
during the lab; accuracy of equipment
15
What sources of error did you encounter in the lab and
what magnitude of effect did it have on the results?
Briefly summarize the highlights of the lab
What did you learn from conducting this lab?
Give at least one recommendation to improve the
accuracy of this lab.
Include all raw data, sample calculations to support your
results obtained above and references.
Appendix/
?
References
Total Points
Attendance/Participation
Final Lab 4 Grade (%)
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10
Describe how the road fill changed with a change in
moisture content
Color, feel, grain size, moisture descriptions
Mention sieves passed for the samples?aka ?? or #4
? Data Table for Standard and Modified
? Graph of Dry Unit Weight vs. Moisture Content
including standard, modified, and zero air void
curves
? Find the max. dry density and the optimum
moisture content
? Discuss the 2 different proctor tests and why
different tests are used; research this online or in the
soils textbook!
? Discuss how the moisture content related to the dry
unit weight and the ease of compaction of the
samples; hint: what does the water do to the soil
particles? Use your result values to defend your
conclusions!
? Discuss why we compact soils and why knowing
the optimum moisture content is so important?to
reduce air content, increase strength, etc?
?
Points
Available
20
20
5
5
80
20
100
Points
Awarded
This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: D1557 – 12?1
Standard Test Methods for
Laboratory Compaction Characteristics of Soil Using
Modified Effort (56,000 ft-lbf/ft3 (2,700 kN-m/m3))1
This standard is issued under the fixed designation D1557; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (?) indicates an editorial change since the last revision or reapproval.
This standard has been approved for use by agencies of the U.S. Department of Defense.
e1 NOTE?Editorially corrected variable for Eq A1.2 in July 2015.
1. Scope*
1.1 These test methods cover laboratory compaction methods used to determine the relationship between molding water
content and dry unit weight of soils (compaction curve)
compacted in a 4- or 6-in. (101.6- or 152.4-mm) diameter mold
with a 10.00-lbf. (44.48-N) rammer dropped from a height of
18.00 in. (457.2 mm) producing a compactive effort of 56 000
ft-lbf/ft3 (2700 kN-m/m3).
NOTE 1?The equipment and procedures are the same as proposed by
the U.S. Corps of Engineers in 1945. The modified effort test (see 3.1.3)
is sometimes referred to as the Modified Proctor Compaction Test.
1.1.1 Soils and soil-aggregate mixtures are to be regarded as
natural occurring fine- or coarse-grained soils, or composites or
mixtures of natural soils, or mixtures of natural and processed
soils or aggregates such as gravel or crushed rock. Hereafter
referred to as either soil or material.
1.2 These test methods apply only to soils (materials) that
have 30 % or less by mass of their particles retained on the
3/4-in. (19.0-mm) sieve and have not been previously compacted in the laboratory; that is, do not reuse compacted soil.
1.2.1 For relationships between unit weights and molding
water contents of soils with 30 % or less by weight of material
retained on the 3/4-in. (19.0-mm) sieve to unit weights and
molding water contents of the fraction passing the 3/4-in.
(19.0-mm) sieve, see Practice D4718.
1.3 Three alternative methods are provided. The method
used shall be as indicated in the specification for the material
being tested. If no method is specified, the choice should be
based on the material gradation.
1.3.1 Method A:
1.3.1.1 Mold?4-in. (101.6-mm) diameter.
1.3.1.2 Material?Passing No. 4 (4.75-mm) sieve.
1
These test methods are under the jurisdiction of ASTM Committee D18 on Soil
and Rock and are the direct responsibility of Subcommittee D18.03 on Texture,
Plasticity and Density Characteristics of Soils.
Current edition approved May 1, 2012. Published June 2012. Originally
approved in 1958. Last previous edition approved in 2007 as D1557 ? 09. DOI:
10.1520/D1557-12.
1.3.1.3 Layers?Five.
1.3.1.4 Blows per layer?25.
1.3.1.5 Usage?May be used if 25 % or less by mass of the
material is retained on the No. 4 (4.75-mm) sieve. However, if
5 to 25 % by mass of the material is retained on the No. 4
(4.75-mm) sieve, Method A can be used but oversize corrections will be required (See 1.4) and there are no advantages to
using Method A in this case.
1.3.1.6 Other Use?If this gradation requirement cannot be
met, then Methods B or C may be used.
1.3.2 Method B:
1.3.2.1 Mold?4-in. (101.6-mm) diameter.
1.3.2.2 Material?Passing 3/8-in. (9.5-mm) sieve.
1.3.2.3 Layers?Five.
1.3.2.4 Blows per layer?25.
1.3.2.5 Usage?May be used if 25 % or less by mass of the
material is retained on the 3/8-in. (9.5-mm) sieve. However, if
5 to 25 % of the material is retained on the 3/8-in. (9.5-mm)
sieve, Method B can be used but oversize corrections will be
required (See 1.4). In this case, the only advantages to using
Method B rather than Method C are that a smaller amount of
sample is needed and the smaller mold is easier to use.
1.3.2.6 Other Usage?If this gradation requirement cannot
be met, then Method C may be used.
1.3.3 Method C:
1.3.3.1 Mold?6-in. (152.4-mm) diameter.
1.3.3.2 Material?Passing 3/4-in. (19.0-mm) sieve.
1.3.3.3 Layers?Five.
1.3.3.4 Blows per layer?56.
1.3.3.5 Usage?May be used if 30 % or less (see 1.4) by
mass of the material is retained on the 3/4-in. (19.0-mm) sieve.
1.3.4 The 6-in. (152.4-mm) diameter mold shall not be used
with Method A or B.
NOTE 2?Results have been found to vary slightly when a material is
tested at the same compactive effort in different size molds, with the
*A Summary of Changes section appears at the end of this standard
Copyright ? ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
Copyright by ASTM Int’l (all rights reserved); Sat Feb 2 20:55:19 EST 2019
1
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Florida Institute Technology (Florida Institute Technology) pursuant to License Agreement. No further reproductions authorized.
D1557 – 12?1
smaller mold size typically yielding larger values of unit weight and
density (1).2
1.4 If the test specimen contains more than 5 % by mass of
oversize fraction (coarse fraction) and the material will not be
included in the test, corrections must be made to the unit
weight and molding water content of the test specimen or to the
appropriate field in-place unit weight (or density) test specimen
using Practice D4718.
1.5 This test method will generally produce a well-defined
maximum dry unit weight for non-free draining soils. If this
test method is used for free-draining soils the maximum unit
weight may not be well defined, and can be less than obtained
using Test Methods D4253.
1.6 All observed and calculated values shall conform to the
guidelines for significant digits and rounding established in
Practice D6026, unless superseded by these test methods.
1.6.1 For purposes of comparing measured or calculated
value(s) with specified limits, the measured or calculated
value(s) shall be rounded to the nearest decimal or significant
digits in the specified limits.
1.6.2 The procedures used to specify how data are collected/
recorded or calculated in this standard are regarded as the
industry standard. In addition, they are representative of the
significant digits that generally should be retained. The procedures used do not consider material variation, purpose for
obtaining the data, special purpose studies, or any considerations for the user?s objectives; it is common practice to
increase or reduce significant digits of reported data to be
commensurate with these considerations. It is beyond the scope
of these test methods to consider significant digits used in
analytical methods for engineering design.
1.7 The values in inch-pound units are to be regarded as the
standard. The values stated in SI units are provided for
information only, except for units of mass. The units for mass
are given in SI units only, g or kg.
1.7.1 It is common practice in the engineering profession to
concurrently use pounds to represent both a unit of mass (lbm)
and a force (lbf). This implicitly combines two separate
systems of units; that is, the absolute system and the gravitational system. It is scientifically undesirable to combine the use
of two separate sets of inch-pound units within a single
standard. These test methods have been written using the
gravitational system of units when dealing with the inch-pound
system. In this system, the pound (lbf) represents a unit of force
(weight). However, the use of balances or scales recording
pounds of mass (lbm) or the recording of density in lbm/ft3
shall not be regarded as a nonconformance with this standard.
1.8 This standard does not purport to address all of the
safety concerns, if any, associated with its use. It is the
responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
1.9 Warning?Mercury has been designated by EPA and
many state agencies as a hazardous material that can cause
2
The boldface numbers in parentheses refer to the list of references at the end of
this standard.
central nervous system, kidney, and liver damage. Mercury, or
its vapor, may be hazardous to health and corrosive to
materials. Caution should be taken when handling mercury and
mercury containing products. See the applicable product Material Safety Data Sheet (MSDS) for details and EPA?s website
(http://www.epa.gov/mercury/faq.htm) for additional information. Users should be aware that selling mercury or mercury
containing products or both into your state may be prohibited
by state law.
2. Referenced Documents
2.1 ASTM Standards:3
C127 Test Method for Relative Density (Specific Gravity)
and Absorption of Coarse Aggregate
C136 Test Method for Sieve Analysis of Fine and Coarse
Aggregates
C670 Practice for Preparing Precision and Bias Statements
for Test Methods for Construction Materials
D653 Terminology Relating to Soil, Rock, and Contained
Fluids
D698 Test Methods for Laboratory Compaction Characteristics of Soil Using Standard Effort (12 400 ft-lbf/ft3 (600
kN-m/m3))
D854 Test Methods for Specific Gravity of Soil Solids by
Water Pycnometer
D2168 Practices for Calibration of Laboratory MechanicalRammer Soil Compactors
D2216 Test Methods for Laboratory Determination of Water
(Moisture) Content of Soil and Rock by Mass
D2487 Practice for Classification of Soils for Engineering
Purposes (Unified Soil Classification System)
D2488 Practice for Description and Identification of Soils
(Visual-Manual Procedure)
D3740 Practice for Minimum Requirements for Agencies
Engaged in Testing and/or Inspection of Soil and Rock as
Used in Engineering Design and Construction
D4220 Practices for Preserving and Transporting Soil
Samples
D4253 Test Methods for Maximum Index Density and Unit
Weight of Soils Using a Vibratory Table
D4718 Practice for Correction of Unit Weight and Water
Content for Soils Containing Oversize Particles
D4753 Guide for Evaluating, Selecting, and Specifying Balances and Standard Masses for Use in Soil, Rock, and
Construction Materials Testing
D4914 Test Methods for Density and Unit Weight of Soil
and Rock in Place by the Sand Replacement Method in a
Test Pit
D5030 Test Method for Density of Soil and Rock in Place by
the Water Replacement Method in a Test Pit
D6026 Practice for Using Significant Digits in Geotechnical
Data
D6913 Test Methods for Particle-Size Distribution (Gradation) of Soils Using Sieve Analysis
3
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contact ASTM Customer Service at [email protected]. For Annual Book of ASTM
Standards volume information, refer to the standard?s Document Summary page on
the ASTM website.
Copyright by ASTM Int’l (all rights reserved); Sat Feb 2 20:55:19 EST 2019
2
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Florida Institute Technology (Florida Institute Technology) pursuant to License Agreement. No further reproductions authorized.
D1557 – 12?1
E11 Specification for Woven Wire Test Sieve Cloth and Test
Sieves
E319 Practice for the Evaluation of Single-Pan Mechanical
Balances
IEEE/ASTM SI 10 Standard for Use of the International
System of Units (SI): The Modern Metric System
3. Terminology
3.1 Definitions:
3.1.1 See Terminology D653 for general definitions.
3.1.2 molding water content, n?the water content of the
soil (material) specimen in the mold after it has been reconstituted and compacted.
3.1.3 modified effort?in compaction testing, the term for
the 56 000 ft-lbf/ft3 (2700 kN-m/m3) compactive effort applied
by the equipment and methods of this test.
3.1.4 modified maximum dry unit weight, ?d,max (lbf/ft3
(kN/m3))?in compaction testing, the maximum value defined
by the compaction curve for a compaction test using modified
effort.
3.1.5 modified optimum water content, wopt (%)?in compaction testing, the water content at which the soil can be
compacted to the maximum dry unit weight using modified
compactive effort.
3.2 Definitions of Terms Specific to This Standard:
3.2.1 oversize fraction (coarse fraction), PC (%)?the portion of total specimen not used in performing the compaction
test; it may be the portion of total specimen retained on the No.
4 (4.75-mm) sieve in Method A, 3/8-in. (9.5-mm) sieve in
Method B, or 3/4-in. (19.0-mm) sieve in Method C.
3.2.2 test fraction (finer fraction), PF (%)?the portion of
the total specimen used in performing the compaction test; it
may be fraction passing the No. 4 (4.75-mm) sieve in Method
A, passing the 3/8-in. (9.5-mm) sieve in Method B, or passing
the 3/4-in. (19.0-mm) sieve in Method C.
4. Summary of Test Method
4.1 A soil at a selected molding water content is placed in
five layers into a mold of given dimensions, with each layer
compacted by 25 or 56 blows of a 10.00-lbf (44.48-N) rammer
dropped from a distance of 18.00 in. (457.2 mm), subjecting
the soil to a total compactive effort of about 56 000 ft-lbf/ft3
(2700 kN-m/m3). The resulting dry unit weight is determined.
The procedure is repeated for a sufficient number of molding
water contents to establish a relationship between the dry unit
weight and the molding water content for the soil. This data,
when plotted, represent a curvilinear relationship known as the
compaction curve. The values of optimum water content and
modified maximum dry unit weight are determined from the
compaction curve.
5. Significance and Use
5.1 Soil placed as engineering fill (embankments, foundation pads, road bases) is compacted to a dense state to obtain
satisfactory engineering properties such as shear strength,
compressibility, or permeability. In addition, foundation soils
are often compacted to improve their engineering properties.
Laboratory compaction tests provide the basis for determining
the percent compaction and molding water content needed to
achieve the required engineering properties, and for controlling
construction to assure that the required compaction and water
contents are achieved.
NOTE 3?The degree of soil compaction required to achieve the desired
engineering properties is often specified as a percentage of the modified
maximum dry unit weight as determined using this test method. If the
required degree of compaction is substantially less than the modified
maximum dry unit weight using this test method, it may be practicable for
testing to be performed using Test Method D698 and to specify the degree
of compaction as a percentage of the standard maximum dry unit weight.
Since more energy is applied for compaction using this test method, the
soil particles are more closely packed than when D698 is used. The
general overall result is a higher maximum dry unit weight, lower
optimum moisture content, greater shear strength, greater stiffness, lower
compressibility, lower air voids, and decreased permeability. However, for
highly compacted fine-grained soils, absorption of water may result in
swelling, with reduced shear strength and increased compressibility,
reducing the benefits of the increased effort used for compaction (2). Use
of D698, on the other hand, allows compaction using less effort and
generally at a higher optimum moisture content. The compacted soil may
be less brittle, more flexible, more permeable, and less subject to effects
of swelling and shrinking. In many applications, building or construction
codes may direct which test method, D698 or this one, should be used
when specifying the comparison of laboratory test results to the degree of
compaction of the in-place soil in the field.
5.2 During design of an engineered fill, testing performed to
determine shear, consolidation, permeability, or other properties requires test specimens to be prepared by compacting the
soil at a prescribed molding water content to obtain a predetermined unit weight. It is common practice to first determine
the optimum water content (wopt) and maximum dry unit
weight (?dmax) by means of a compaction test. Test specimens
are compacted at a selected molding water content (w), either
wet or dry of optimum (wopt) or at optimum (wopt), and at a
selected dry unit weight related to a percentage of maximum
dry unit weight (?dmax). The selection of molding water content
(w), either wet or dry of optimum (wopt) or at optimum (wopt)
and the dry unit weight (?dmax) may be based on past
experience, or a range of values may be investigated to
determine the necessary percent of compaction.
5.3 Experience indicates that the methods outlined in 5.2 or
the construction control aspects discussed in 5.1 are extremely
difficult to implement or yield erroneous results when dealing
with some soils. The following subsections describe typical
problem soils, the problems encountered when dealing with
such soils and possible solutions for these problems.
5.3.1 Oversize Fraction?Soils containing more than 30 %
oversize fraction (material retained on the 3/4-in. (19-mm)
sieve) are a problem. For such soils, there is no ASTM test
method to control their compaction and very few laboratories
are equipped to determine the laboratory maximum unit weight
(density) of such soils (USDI Bureau of Reclamation, Denver,
CO and U.S. Army Corps of Engineers, Vicksburg, MS).
Although Test Methods D4914 and D5030 determine the
?field? dry unit weight of such soils, they are difficult and
expensive to perform.
5.3.1.1 One method to design and control the compaction of
such soils is to use a test fill to determine the required degree
of compaction and the method to obtain that compaction. Then
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D1557 – 12?1
use a method specification to control the compaction. Components of a method specification typically contain the type and
size of compaction equipment to be used, the lift thickness,
acceptable range of molding water content, and number of
passes.
NOTE 4?Success in executing the compaction control of an earthwork
project, especially when a method specification is used, is highly
dependent upon the quality and experience of the contractor and inspector.
5.3.1.2 Another method is to apply the use of density
correction factors developed by the USDI Bureau of Reclamation (3,4) and U.S. Corps of Engineers (5). These correction
factors may be applied for soils containing up to about 50 to
70 % oversize fraction. Both agencies use a different term for
these density correction factors. The USDI Bureau of Reclamation uses D ratio (or D ? VALUE), while the U.S. Corps of
Engineers uses Density Interference Coefficient (Ic).
5.3.1.3 The use of the replacement technique (Test Method
D1557?78, Method D), in which the oversize fraction is
replaced with a finer fraction, is inappropriate to determine the
maximum dry unit weight, ?dmax, of soils containing oversize
fractions (5).
5.3.2 Degradation?Soils containing particles that degrade
during compaction are a problem, especially when more
degradation occurs during laboratory compaction than field
compaction, the typical case. Degradation typically occurs
during the compaction of a granular-residual soil or aggregate.
When degradation occurs, the maximum dry-unit weight increases (1) so that the resulting laboratory maximum value is
not representative of field conditions. Often, in these cases, the
maximum dry unit weight is impossible to achieve in the field.
5.3.2.1 Again for soils subject to degradation, the use of test
fills and method specifications may help. Use of replacement
t
