ASTM D1883-16

Designation: D1883 − 16Standard Test Method forCalifornia Bearing Ratio (CBR) of Laboratory-CompactedSoils1This standard is issued under the fixed designation D1883; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript 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.1. Scope*1.1 This test method covers the determination of the Cali-fornia Bearing Ratio (CBR) of pavement subgrade, subbase,and base course materials from laboratory compacted speci-mens. The test method is primarily intended for, but not limitedto, evaluating the strength of materials having maximumparticle size less than3⁄4 in. (19 mm).1.2 When materials having a maximum particle size greaterthan3⁄4 in. (19 mm) are to be tested, this test method providesfor modifying the gradation of the material so that the materialused for testing all passes the3⁄4-in. (19-mm) sieve while thetotal gravel fraction (material passing the 3-in. (75-mm) sieveand retained on the No. 4 (4.75-mm) sieve) remains the same.While traditionally this method of specimen preparation hasbeen used to avoid the error inherent in testing materialscontaining large particles in the CBR test apparatus, themodified material may have significantly different strengthproperties than the original material. However, a large experi-ence database has been developed using this test method formaterials for which the gradation has been modified, andsatisfactory design methods are in use based on the results oftests using this procedure.1.3 Past practice has shown that CBR results for thosematerials having substantial percentages of particles retainedon the No. 4 (4.75 mm) sieve are more variable than for finermaterials. Consequently, more trials may be required for thesematerials to establish a reliable CBR.1.4 This test method provides for the determination of theCBR of a material at optimum water content or a range ofwater content from a specified compaction test and a specifieddry unit weight. The dry unit weight is usually given as apercentage of maximum dry unit weight determined by TestMethods D698 or D1557.1.5 The client requesting the test may specify the watercontent or range of water contents and the dry unit weight forwhich the CBR is desired.1.6 Unless specified otherwise by the requesting client, orunless it has been shown to have no effect on test results for thematerial being tested, all specimens shall be soaked prior topenetration.1.7 For the determination of CBR of field in-placematerials, see Test Method D4429.1.8 Units—The values stated in inch-pound units are to beregarded as standard. The SI units given in parentheses aremathematical conversions, which are provided for informationpurposes only and are not considered standard. Reporting oftest results in units other than inch-pound units shall not beregarded as nonconformance with this test method.1.8.1 The gravitational system of inch-pound units is usedwhen dealing with inch-pound units. In this system, the pound(lbf) represents a unit of force (weight), while the unit for massis slugs. The slug unit is not given, unless dynamic (F = ma)calculations are involved.1.8.2 The slug unit of mass is almost never used incommercial practice; that is, density, balances, etc. Therefore,the standard unit for mass in this standard is either kilogram(kg) or gram (g), or both. Also, the equivalent inch-pound unit(slug) is not given/presented in parentheses.1.8.3 It is common practice in the engineering/constructionprofession, in the United States, to concurrently use pounds torepresent both a unit of mass (lbm) and of force (lbf). Thisimplicitly combines two separate systems of units; that is, theabsolute system and the gravitational system. It is scientificallyundesirable to combine the use of two separate sets ofinchpound units within a single standard. As stated, thisstandard includes the gravitational system of inch-pound unitsand does not use/present the slug unit for mass. However, theuse of balances or scales recording pounds of mass (lbm) orrecording density in lbm/ft3shall not be regarded as noncon-formance with this standard.1.8.4 The terms density and unit weight are often usedinterchangeably. Density is mass per unit volume whereas unitweight is force per unit volume. In this standard, density is1This test method is under the jurisdiction ofASTM Committee D18 on Soil andRock and is the direct responsibility of Subcommittee D18.05 on Strength andCompressibility of Soils.Current edition approved March 1, 2016. Published March 2016. Originallyapproved in 1961. Last previous edition approved in 2014 as D1883 – 14. DOI:10.1520/D1883-16.*A Summary of Changes section appears at the end of this standardCopyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States1given only in SI units. After the density has been determined,the unit weight is calculated in SI or inch-pound units, or both.1.9 All observed and calculated values shall conform to theguidelines for significant digits and rounding established inPractice D6026.1.9.1 The procedures used to specify how data are collected/recorded or calculated in this standard are regarded as theindustry standard. In addition they are representative of thesignificant digits that generally should be retained. The proce-dures used do not consider material variation, purpose forobtaining the data, special purpose studies, or any consider-ations for the user’s objectives, and it is common practice toincrease or reduce significant digits of reported data to becommensurate with these considerations. It is beyond the scopeof this standard to consider significant digits used in analyticalmethods for engineering design.1.10 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2C670 Practice for Preparing Precision and Bias Statementsfor Test Methods for Construction MaterialsD422 Test Method for Particle-Size Analysis of Soils (With-drawn 2016)3D653 Terminology Relating to Soil, Rock, and ContainedFluidsD698 Test Methods for Laboratory Compaction Character-istics of Soil Using Standard Effort (12,400 ft-lbf/ft3(600kN-m/m3))D1557 Test Methods for Laboratory Compaction Character-istics of Soil Using Modified Effort (56,000 ft-lbf/ft3(2,700 kN-m/m3))D2168 Practices for Calibration of Laboratory Mechanical-Rammer Soil CompactorsD2216 Test Methods for Laboratory Determination of Water(Moisture) Content of Soil and Rock by MassD2487 Practice for Classification of Soils for EngineeringPurposes (Unified Soil Classification System)D2488 Practice for Description and Identification of Soils(Visual-Manual Procedure)D3740 Practice for Minimum Requirements for AgenciesEngaged in Testing and/or Inspection of Soil and Rock asUsed in Engineering Design and ConstructionD4318 Test Methods for Liquid Limit, Plastic Limit, andPlasticity Index of SoilsD4429 Test Method for CBR (California Bearing Ratio) ofSoils in PlaceD4753 Guide for Evaluating, Selecting, and Specifying Bal-ances and Standard Masses for Use in Soil, Rock, andConstruction Materials TestingD6026 Practice for Using Significant Digits in GeotechnicalDataE11 Specification for Woven Wire Test Sieve Cloth and TestSieves3. Terminology3.1 Definitions:3.1.1 For common definitions of terms in this standard, referto Terminology D653.3.2 Definitions of Terms Specific to This Standard:3.2.1 water content of the compaction specimen, wi—watercontent in percent of material used to compact the testspecimen.3.2.2 water content top 1 in. (25.4-mm) after soakingws—water content in percent of upper 1 in. (25.4 mm) ofmaterial removed from the compacted specimen after soakingand penetration.3.2.3 water content after testing, wf—water content in per-cent of the compacted specimen after soaking and finalpenetration; does not include material described in 3.2.2.3.2.4 dry density as compacted and before soaking, ρdi—drydensity of the as compacted test specimen using the measuredwet mass and calculating the dry mass using the water contentdefined in 3.2.1.4. Summary of Test Method4.1 The California Bearing Ratio (CBR) test is used inevaluating subgrade, subbase and base materials as an aid tothe design of pavements. The laboratory test uses a circularpiston to penetrate material compacted in a mold at a constantrate of penetration. The CBR is expressed as the ratio of theunit load on the piston required to penetrate 0.1 in. (2.5 mm)and 0.2 in (5.1 mm) of the test material to the unit load requiredto penetrate a standard material of well-graded crushed stone.4.2 This test method is used to determine the CBR of amaterial compacted in a specified mold. It is incumbent on therequesting client to specify the scope of testing to satisfy theclient’s protocol or specific design requirements. Possiblescope of testing includes:4.2.1 CBR penetration tests can be performed on each pointof a compaction test performed in accordance with Method Cof D698 or D1557. The CBR mold with the spacer diskspecified in this standard has the same internal dimensions asa 6.000-in. (152.4-mm) diameter compaction mold.4.2.2 Another alternative is for the CBR test to be per-formed on material compacted to a specific water content anddensity. Alternatively, a water content range may be stated forone or more density values and will often require a series ofspecimens prepared using two or three compactive efforts forthe specified water contents or over the range of water contentsrequested. The compactive efforts are achieved by followingprocedures of D698 or D1557 but varying the blows per layerto produce densities above and below the desired density.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at service@astm.org. For Annual Book of ASTMStandards volume information, refer to the standard’s Document Summary page onthe ASTM website.3The last approved version of this historical standard is referenced onwww.astm.org.D1883 − 1625. Significance and Use5.1 This test method is used to evaluate the potentialstrength of subgrade, subbase, and base course materials,including recycled materials for use in the design of road andairfield pavements. The CBR value obtained in this test formsan integral part of several flexible pavement design methods.5.2 For applications where the effect of compaction watercontent on CBR is small, such as cohesionless, coarse-grainedmaterials, or where an allowance is made for the effect ofdiffering compaction water contents in the design procedure,the CBR may be determined at the optimum water content ofa specified compaction effort. The specified dry unit weight isnormally the minimum percent compaction allowed by theusing client’s field compaction specification.5.3 For applications where the effect of compaction watercontent on CBR is unknown or where it is desired to accountfor its effect, the CBR is determined for a range of watercontents, usually the range of water content permitted for fieldcompaction by using the client’s protocol or specification forfield compaction.5.4 The criteria for test specimen preparation of self-cementing (and other) materials which gain strength with timemust be based on a geotechnical engineering evaluation. Asdirected by the client, self-cementing materials shall be prop-erly cured until bearing ratios representing long term serviceconditions can be measured.NOTE 1—The quality of the results produced by this standard isdependent on the competence of the personnel performing it, and thesuitability of the equipment and facilities used. Agencies that meet thecriteria of Practice D3740 are generally considered capable of competentand objective testing/sampling/inspection/etc. Users of this standard arecautioned that compliance with Practice D3740 does not in itself ensurereliable results. Reliable results depend on many factors; Practice D3740provides a means of evaluating some of those factors.6. Apparatus6.1 Loading Machine—The loading machine shall beequipped with a movable head or base that travels at a uniform(not pulsating) rate of 0.05 in. (1.3 mm)/min for use in pushingthe penetration piston into the specimen. The load rate of 0.05in. (1.3 mm)/min shall be maintained within 620% over therange of loads developed during penetration. The minimumcapacity of the loading machine shall be based on the require-ments indicated in Table 1.6.1.1 The machine shall be equipped with a load-indicatingdevice matched to the anticipated maximum penetration load.The load-indicating device shall have a minimum accuracy of:10 lbf (44 N) or less for a 10,000 lbf (44 kN) capacity; 5 lbf (22N) or less for 5,000 lbf (22 kN) and 2 lbf (9 N) or less for 2,500lbf (11 kN).6.2 Penetration Measuring Device—The penetration mea-suring device (such as a mechanical dial indicator or electronicdisplacement transducer) shall be capable of reading to thenearest 0.001 in. (0.025 mm) and provided with appropriatemounting hardware. The mounting assembly of the deforma-tion measuring device shall be connected to the penetratingpiston and the edge of the mold providing accurate penetrationmeasurements. Mounting the deformation holder assembly to astressed component of the load frame (such as tie rods) willintroduce inaccuracies of penetration measurements.6.3 Mold—The mold shall be a rigid metal cylinder with aninside diameter of 6.000 6 0.026 in. (152.4 6 0.66 mm) anda height of 7.000 6 0.018 in. (177.8 6 0.46 mm). It shall beprovided with a metal extension collar at least 2.0 in. (50.8mm) in height and a metal base plate having at least twentyeight1⁄16-in. (1.59-mm) diameter holes uniformly spaced overthe plate within the inside circumference of the mold. Whenassembled with the spacer disc placed in the bottom of themold, the mold shall have an internal volume (excludingextension collar) of 0.0750 6 0.0009 ft3(2124 6 25 cm3). Amold assembly having the minimum required features is shownin Fig. 1. A calibration procedure shall be used to confirm theactual volume of the mold with the spacer disk inserted.Suitable calibration procedures are contained in Test MethodsD698 and D1557.6.4 Spacer Disk—A circular metal spacer disc (see Fig. 1)having a minimum outside diameter of 515⁄16 in. (150.8 mm)but no greater than will allow the spacer disc to easily slip intothe mold. The spacer disc shall be 2.416 6 0.005 in. (61.37 60.13 mm) in height.6.5 Rammer—A rammer as specified in either Test MethodsD698 or D1557 except that if a mechanical rammer is used it