ASTM D1883-99
(Test Method)Standard Test Method for CBR (California Bearing Ratio) of Laboratory-Compacted Soils
Standard Test Method for CBR (California Bearing Ratio) of Laboratory-Compacted Soils
SCOPE
1.1 This test method covers the determination of the CBR (California Bearing Ratio) of pavement subgrade, subbase, and base/course materials from laboratory compacted specimens. The test method is primarily intended for but not limited to, evaluating the strength of cohesive materials having maximum particle sizes less than 3/4 in. (19 mm). Note 1-The agency performing this test can be evaluated in accordance with Practice D3740. Not withstanding statements on precision and bias contained in this Standard: The precision of this test method is dependent on the competence of the personnel performing it and the suitability of the equipment and facilities used. Agencies which meet the criteria of Practice D3740 are generally considered capable of competent and objective testing. Users of this method are cautioned that compliance with Practice D3740 does not in itself assure reliable testing. Reliable testing depends on many factors; Practice D3740 provides a means of evaluating some of those factors.
1.2 When materials having maximum particle sizes greater than 3/4 in. (19 mm) are to be tested, this test method provides for modifying the gradation of the material so that the material used for tests all passes the 3/4-in. sieve while the total gravel (+No. 4 to 3 in.) fraction remains the same. While traditionally this method of specimen preparation has been used to avoid the error inherent in testing materials containing large particles in the CBR test apparatus, the modified material may have significantly different strength properties than the original material. However, a large experience base has developed using this test method for materials for which the gradation has been modified, and satisfactory design methods are in use based on the results of tests using this procedure.
1.3 Past practice has shown that CBR results for those materials having substantial percentages of particles retained on the No. 4 sieve are more variable than for finer materials. Consequently, more trials may be required for these materials to establish a reliable CBR.
1.4 This test method provides for the determination of the CBR of a material at optimum water content or a range of water content from a specified compaction test and a specified dry unit weight. The dry unit weight is usually given as a percentage of maximum dry unit weight from the compaction tests of Test Methods D698 or D1557.
1.5 The agency requesting the test shall specify the water content or range of water content and the dry unit weight for which the CBR is desired.
1.6 Unless specified otherwise by the requesting agency, or unless it has been shown to have no effect on test results for the material being tested, all specimens shall be soaked prior to penetration.
1.7 For the determination of CBR of field compacted materials, see Test Method D4429.
1.8 The values stated in inch-pound units are to be regarded as the standard. The SI equivalents shown in parentheses may be approximate.
1.9 This standard does not purport to address all of the safety problems, 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.
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Designation:D1883–99
Standard Test Method for
CBR (California Bearing Ratio) of Laboratory-Compacted
Soils
This standard is issued under the fixed designation D 1883; 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 (e) indicates an editorial change since the last revision or reapproval.
This standard has been approved for use by agencies of the Department of Defense.
1. Scope* 1.4 This test method provides for the determination of the
CBR of a material at optimum water content or a range of
1.1 This test method covers the determination of the CBR
water content from a specified compaction test and a specified
(California Bearing Ratio) of pavement subgrade, subbase, and
dry unit weight. The dry unit weight is usually given as a
base/course materials from laboratory compacted specimens.
percentage of maximum dry unit weight from the compaction
The test method is primarily intended for but not limited to,
tests of Test Methods D 698 or D 1557.
evaluating the strength of cohesive materials having maximum
3 1.5 The agency requesting the test shall specify the water
particle sizes less than ⁄4 in. (19 mm).
content or range of water content and the dry unit weight for
NOTE 1—The agency performing this test can be evaluated in accor-
which the CBR is desired.
dance with Practice D 3740.
1.6 Unless specified otherwise by the requesting agency, or
Not withstanding statements on precision and bias contained in this
unless it has been shown to have no effect on test results for the
Standard: The precision of this test method is dependent on the compe-
material being tested, all specimens shall be soaked prior to
tence of the personnel performing it and the suitability of the equipment
and facilities used. Agencies which meet the criteria of Practice D 3740 penetration.
aregenerallyconsideredcapableofcompetentandobjectivetesting.Users
1.7 For the determination of CBR of field compacted
of this method are cautioned that compliance with Practice D 3740 does
materials, see Test Method D 4429.
not in itself assure reliable testing. Reliable testing depends on many
1.8 The values stated in inch-pound units are to be regarded
factors; Practice D 3740 provides a means of evaluating some of those
as the standard. The SI equivalents shown in parentheses may
factors.
be approximate.
1.2 When materials having maximum particle sizes greater
1.9 This standard does not purport to address all of the
than ⁄4 in. (19 mm) are to be tested, this test method provides
safety problems, if any, associated with its use. It is the
for modifying the gradation of the material so that the material
responsibility of the user of this standard to establish appro-
used for tests all passes the ⁄4-in. sieve while the total gravel
priate safety and health practices and determine the applica-
( +No.4to3in.)fractionremainsthesame.Whiletraditionally
bility of regulatory limitations prior to use.
thismethodofspecimenpreparationhasbeenusedtoavoidthe
error inherent in testing materials containing large particles in 2. Referenced Documents
the CBR test apparatus, the modified material may have
2.1 ASTM Standards:
significantly different strength properties than the original
D 422 Test Method for Particle-Size Analysis of Soils
material. However, a large experience base has developed
D 653 Terminology Relating to Soil, Rock, and Contained
using this test method for materials for which the gradation has
Fluids
been modified, and satisfactory design methods are in use
D 698 Test Method for Laboratory Compaction Character-
based on the results of tests using this procedure.
istics of Soil Using Standard Effort (12,400 ft-lbf/ft (600
3 2
1.3 Past practice has shown that CBR results for those
kN-m/m ))
materials having substantial percentages of particles retained
D 1557 Test Method for Laboratory Compaction Character-
on the No. 4 sieve are more variable than for finer materials.
istics of Soil Using Modified Effort (56,000 ft-lbf/ft
Consequently, more trials may be required for these materials
(2,700 kN-m/m ))
to establish a reliable CBR.
D 2168 Test Methods for Calibration of Laboratory
Mechanical-Rammer Soil Compactors
D 2216 TestMethodforLaboratoryDeterminationofWater
(Moisture) Content of Soil and Rock
This test method is underthejurisdictionofASTMCommitteeD18onSoiland
Rock and is the direct responsibility of Subcommittee D18.05 on Strength and
Compressibility of Soils.
Current edition approved Feb. 10, 1999. Published May 1999. Originally
published as D 1883 – 61T. Last previous edition D 1883 – 94. Annual Book of ASTM Standards, Vol 04.08.
*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.
D1883–99
D 2487 Classification of Soils for Engineering Purposes properly cured until bearing ratios representing long term
(Unified Soil Classification System) service conditions can be measured.
D 2488 Practice for Description and Identification of Soils
5. Apparatus
(Visual-Manual Procedure)
D 3740 Practice for Minimum Requirements of Agencies 5.1 Loading Machine—The loading machine shall be
Engaged in the Testing and/or Inspection of Soil and Rock
equipped with a movable head or base that travels at a uniform
as Used in Engineering Design and Construction (notpulsating)rateof0.05in.(1.27mm)/minforuseinforcing
D 4318 Test Method for Liquid Limit, Plastic Limit, and
the penetration piston into the specimen. The machine shall be
Plasticity Index of Soils equipped with a load-indicating device that can be read to 10
D 4429 Test Method for CBR (California Bearing Ratios) lbf (44 N) or less. The minimum capacity of the loading
of Soils in Place machine shall be based on the requirements indicated in Table
1.
5.2 Mold—The mold shall be a rigid metal cylinder with an
3. Summary of Test Method
inside diameter of 6 6 0.026 in. (152.4 6 0.66 mm) and a
3.1 For tests performed on materials compacted to one
heightof7 60.018in.(177.8 60.46mm).Itshallbeprovided
water content, three specimens are prepared. The specimens
with a metal extension collar at least 2.0 in. (50.8 mm) in
are compacted using three different compactive efforts to
height and a metal base plate having at least twenty eight
obtain unit weights both above and below the desired unit
⁄16-in. (1.59-mm) diameter holes uniformly spaced over the
weight.After allowing specimens to take on water by soaking,
plate within the inside circumference of the mold. When
or other specified treatment such as curing, each specimen is
assembled with spacer disc in place in the bottom of the mold,
subjected to penetration by a cylindrical rod. Results of stress
the mold shall have an internal volume (excluding extension
(load) versus penetration depth are plotted to determine the
collar) of 0.075 6 0.0009 ft (2124 6 25 cm). Fig. 1 shows a
CBR for each specimen. The CBR at the specified density is
satisfactory mold design. A calibration procedure should be
determined from a graph of CBR versus dry unit weight.
used to confirm the actual volume of the mold with the spacer
3.2 For tests in which the result is to be determined for a
disk inserted. Suitable calibrations are contained in Test
water content range, a series of specimens at each of three
Methods D 698 and D 1557.
compactiveeffortsarepreparedovertherangeofwatercontent
5.3 Spacer Disk—A circular metal spacer disc (see Fig. 1)
of interest. The compactive efforts are chosen to produce unit
having a minimum outside diameter of 5 ⁄16 in. (150.8 mm)
weights above and below the desired unit weight. After
but no greater than will allow the spacer to easily slip into the
allowing the specimens to take on water by soaking, or other
mold. The spacer disc shall be 2.4166 0.005 in. (61.37 6
specified treatment such as curing, each specimen is pen-
0.127 mm) in height.
etrated. Results are plotted to obtain the CBR for each
5.4 Rammer—Arammer as specified in eitherTest Methods
specimen. A plot of CBR versus unit weight for each water
D 698 or D 1557 except that if a mechanical rammer is used it
content is made to determine the minimum CBR for the water
must be equipped with a circular foot, and when so equipped,
content range of interest.
must provide a means for distributing the rammer blows
uniformly over the surface of the soil when compacting in a
4. Significance and Use
6-in.(152.4-mm)diametermold.Themechanicalrammermust
4.1 This test method is used to evaluate the potential
be calibrated and adjusted in accordance with Test Methods
strength of subgrade, subbase, and base course material,
D 2168.
including recycled materials for use in road and airfield
5.5 Expansion-MeasuringApparatus—An adjustable metal
pavements. The CBR value obtained in this test forms an
stem and perforated metal plate, similar in configuration to that
integral part of several flexible pavement design methods.
7 15
shown in Fig. 1. The perforated plate shall be 5 ⁄8 to 5 ⁄16 in.
4.2 For applications where the effect of compaction water
(149.23 to 150.81 mm) in diameter and have at least forty-two
content on CBR is small, such as cohesionless, coarse-grained
⁄16-in. (1.59-mm) diameter holes uniformly spaced over the
materials, or where an allowance is made for the effect of
plate.Ametal tripod to support the dial gage for measuring the
differing compaction water contents in the design procedure,
amount of swell during soaking is also required.
the CBR may be determined at the optimum water content of
5.6 Weights—One or two annular metal weights having a
a specified compaction effort. The dry unit weight specified is
total mass of 4.54 6 0.02 kg and slotted metal weights each
normally the minimum percent compaction allowed by the
having masses of 2.27 6 0.02 kg. The annular weight shall be
using agency’s field compaction specification.
7 15
5 ⁄8 to 5 ⁄16 in. (149.23 to 150.81 mm) in diameter and shall
4.3 For applications where the effect of compaction water
have a center hole of approximately 2 ⁄8 in. (53.98 mm).
content on CBR is unknown or where it is desired to account
for its effect, the CBR is determined for a range of water
TABLE 1 Minimum Load Capacity
content, usually the range of water content permitted for field
Maximum Measurable CBR Minimum Load Capacity
compaction by using agency’s field compaction specification.
(lbf) (kN)
4.4 The criteria for test specimen preparation of self ce-
20 2500 11.2
menting (and other) materials which gain strength with time
50 5000 22.3
must be based on a geotechnical engineering evaluation. As
>50 10 000 44.5
directed by the engineer, self cementing materials shall be
D1883–99
TABLE 2 Metric Equivalents
Inch-Pound Metric Metric Metric
Inch-Pound Inch-Pound
Units, in. Equivalent, Equivalent, Equivalent,
Units, in. Units, in.
mm mm mm
19 1
0.003 0.076 ⁄32 15.08 3 ⁄2 88.90
5 3
0.005 0.127 ⁄8 15.88 3 ⁄4 95.25
3 1
0.135 3.43 ⁄4 19.10 4 ⁄4 108.0
15 1
0.201 5.11 ⁄16 23.81 4 ⁄2 114.3
0.4375 11.11 1 25.40 4 ⁄4 120.7
1 7
0.4378 11.12 1 ⁄8 28.58 5 ⁄8 149.2
1 15
0.510 12.95 1 ⁄4 31.8 5 ⁄16 150.8
0.633 16.08 1 ⁄8 34.9 6 152.0
1 7
1.370 34.60 1 ⁄2 38.10 6 ⁄32 158.0
3 1
1.375 34.93 1 ⁄4 44.5 6 ⁄2 165.1
1.954 49.63 1 ⁄16 46.04 7 177.8
15 1
2.416 61.37 1 ⁄16 49.21 7 ⁄2 190.1
1 3
⁄16 1.59 2 50.80 8 ⁄8 212.7
7 1 1
⁄32 5.56 2 ⁄8 53.98 8 ⁄2 215.9
1 1 3
⁄4 6.35 2 ⁄5 55.9 9 ⁄8 238.1
3 1 1
⁄8 9.53 2 ⁄4 57.2 14 ⁄4 362.0
7 1
⁄16 11.11 2 ⁄2 63.50 18 457.2
15 3 1
⁄32 11.91 2 ⁄4 69.85 32 ⁄4 719.2
1 31 5
⁄2 12.70 2 ⁄32 75.41 36 ⁄8 930.3
⁄32 13.49 3 76.20 39 990.6
Inch-Pound Metric Inch-Pound Metric
Units, lb Equivalent, kg Units, psi Equivalent, MPa
0.04 0.02 200 1.4
0.05 0.02 400 2.8
0.12 0.05 600 4.1
0.59 0.27 800 5.5
0.71 0.32 1000 6.9
0.75 0.34 1200 8.3
3.20 1.45 1400 9.7
5.00 2.27
10.00 4.54
5.7 Penetration Piston—A metal piston 1.954 6 0.005 in. compaction test with a sufficient number of test specimens to
(49.63 6 0.13 mm) in diameter and not less than 4 in. (101.6 definitely establish the optimum water content for the soil
mm) long (see Fig. 1). If, from an operational standpoint, it is using the compaction method specified, either Test Methods
advantageous to use a piston of greater length, the longer D 698 or D 1557. A previously performed compaction test on
piston may be used. the same material may be substituted for the compaction test
5.8 Gages—Two dial gages reading to 0.001 in. (0.025 mm) just described, provided that if the sample contains material
with a range of 0.200 minimum. retainedonthe ⁄4-in.(19-mm)sieve,soilpreparedasdescribed
5.9 Miscellaneous Apparatus—Other general apparatus in 6.1 is used (Note 1).
such as a mixing bowl, straightedge, scales, soaking tank or
NOTE 2—Maximum dry unit weight obtained from a compaction test
pan, oven, fast filtering high wet strength filter paper, dishes,
performed in a 4-in. (101.6-mm) diameter mold may be slightly greater
and 2-in., ⁄4-in. and No. 4 sieves.
than the maximum dry unit weight obtained from compaction in the 6-in.
(152.4-mm) compaction mold or CBR mold.
6. Sample
7.1.1 For cases where the CBR is desired at 100 % maxi-
6.1 The sample shall be handled and specimen(s) for com-
mum dry unit weight and optimum water content, compact a
paction shall be prepared in accordance with the procedures
specimen using the specified compaction procedure, eitherTest
given in Test Methods D 698 or D 1557 for compaction in a
Methods D 698 or D 1557, from soil prepared to within 60.5
6-in. (152.4-mm) mold except as follows:
percentage point of optimum water content in accordance with
6.1.1 If all material passes a ⁄4-in. (19-mm) sieve, the entire
Test Method D 2216.
gradationshallbeusedforpreparingspecimensforcompaction
without modification. If there is material retained on the ⁄4-in.
NOTE 3—Where the maximum dry unit weight was determined from
compaction in the 4-in. (101.6-mm) mold, it may be necessary to compact
(19-mm) sieve, the material retained on the ⁄4-in. (19-mm)
specimens as described in 7.1.2, using 75 blows per layer or some other
sieve shall be removed and replaced by an equal amount of
value sufficient to produce a specimen having a density equal to or greater
material passing the ⁄4-in. (19-mm) sieve and retained on the
than that required.
No. 4 sieve obtained by separation from portions of the sample
not otherwise used for testing. 7.1.2 Where the CBR is desired at optimum water content
and some percentage of maximum dry unit weight, compact
7. Test Specimens
three specimens from soil prepared to within 60.5 percentage
7.1
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