Standard Test Method for CBR (California Bearing Ratio) of Laboratory-Compacted Soils

SIGNIFICANCE AND USE
This test method is used to evaluate the potential strength of subgrade, subbase, and base course material, including recycled materials for use in road and airfield pavements. The CBR value obtained in this test forms an integral part of several flexible pavement design methods.  
For applications where the effect of compaction water content on CBR is small, such as cohesionless, coarse-grained materials, or where an allowance is made for the effect of differing compaction water contents in the design procedure, the CBR may be determined at the optimum water content of a specified compaction effort. The dry unit weight specified is normally the minimum percent compaction allowed by the using agency’field compaction specification.
For applications where the effect of compaction water content on CBR is unknown or where it is desired to account for its effect, the CBR is determined for a range of water contents, usually the range of water content permitted for field compaction by using agency’field compaction specification.
The criteria for test specimen preparation of self cementing (and other) materials which gain strength with time must be based on a geotechnical engineering evaluation. As directed by the engineer, self cementing materials shall be properly cured until bearing ratios representing long term service conditions can be measured.
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 1The agency performing this test can be evaluated in accordance with Practice D 3740.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 D 3740 are generally considered capable of competent and objective testing. Users of this method are cautioned that compliance with Practice D 3740 does not in itself assure reliable testing. Reliable testing depends on many factors; Practice D 3740 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 determined by Test Methods D 698 or D 1557.
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 ...

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31-Oct-2005
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ASTM D1883-05 - Standard Test Method for CBR (California Bearing Ratio) of Laboratory-Compacted Soils
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NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information
Designation:D1883–05
Standard Test Method for
CBR (California Bearing Ratio) of Laboratory-Compacted
1
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 determined by Test
The test method is primarily intended for but not limited to,
Methods D 698 or D 1557.
evaluating the strength of cohesive materials having maximum
1.5 The agency requesting the test shall specify the water
3
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
unlessithasbeenshowntohavenoeffectontestresultsforthe
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
penetration.
and facilities used. Agencies which meet the criteria of Practice D 3740
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
3
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-
3
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
2
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 698 Test Method for Laboratory Compaction Character-
3
using this test method for materials for which the gradation has
istics of Soil Using Standard Effort (12,400 ft-lbf/ft (600
3
been modified, and satisfactory design methods are in use
kN-m/m ))
based on the results of tests using this procedure.
D 1557 Test Method for Laboratory Compaction Character-
3
1.3 Past practice has shown that CBR results for those
istics of Soil Using Modified Effort (56,000 ft-lbf/ft
3
materials having substantial percentages of particles retained
(2,700 kN-m/m ))
on the No. 4 sieve are more variable than for finer materials.
D 2168 Test Methods for Calibration of Laboratory
Consequently, more trials may be required for these materials
Mechanical-Rammer Soil Compactors
to establish a reliable CBR.
D 2216 TestMethodforLaboratoryDeterminationofWater
(Moisture) Content of Soil and Rock
1
ThistestmethodisunderthejurisdictionofASTMCommitteeD18onSoiland
Rock and is the direct responsibility of Subcommittee D18.05 on Strength and 2
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Compressibility of Soils.
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
Current edition approved Nov. 1, 2005. Published December 2005. Originally
Standards volume information, refer to the standard’s Document Summary page on
approved in 1961. Last previous edition appr
...

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