676 METHOOS OF SAMPLlNG ANO TESTING TI93

Standard M ethod of Test for

Tbe California Bearing Ratlo

AASHTO DESIGNATlON: T 193-81

l. SCOPE

1.1 This method of test is intended for determining the bearing value of soils and soil-aggregates when they are compacted in the laboratory at optimum moisture content to varying

degrees of density using a S.S lb (2.49 kg) hammer dropped from a height of 12 in. (30S mm). The testis useful for evaluating subgrade soils and some subbase and base course materials containing only asmall amount of material retained on the 19.0 mm (3/4 in.) sieve.

2. APPARATUS

2.1 Molds- The molds shall be cylindrical in shape, made of metal, with an internal ¡liameter of6.0 IO.026 in. (lS2.4 IO.66 mm) and a height of 7.0 IO.016 in. (177.8 IO.66 mm) provideu with anextension collar approximately 2.0 in. (Sl mm) in height and a perforated base plate that can be fitted toeilher end of the mold (See Fig. 1). It is desirable to have at least 3 molds for each soil to be tested.

2.2 Spacer Disk-A circular spacer disk made of metal, 5 15/16:i: 1/32 in. (150.8:i: 0.8 mm)in diameter and 2.4 l 6:i: 0.005 in. (61.4:i: 0.1 mm) in height (see Fig. 1).

NOTEI-When usingmoldshavinga heightof7.0 in. (177.8mm)(seeFig. 1).a spacerdiskheighlof 2.416in. (61.37mm)is neededtoobtaina thicknessof compacledspecimenIhalconformslo Ihethickness:4.584in. (116.43mm)of specimensinAASHTOT 99andT 180.

2.3 Rammer-A rammer weighing 5.50 lb. (2.49 kg) and having a 2 in. (50.8 mm) diameter cir-cular striking Cace,or sector Caceof the same afea. It is equipped to control the height of drop to afree fall of 12 in. (305 mm) above the top elevation of the soil. These are the metal rammers specifiedin AASHTO T 99.

2.4 Apparatus for Measuring Expansion- This consists of a swell plate with adjustable stem(Fig. 1) and a tripod support for a dial indicator (Fig. 1). The swell plate is made of metal, S 718 in.(l49.2 mm) in diameter and is perforated with 1/16 in. (l.6 mm) diameter botes. The tripod used tosupport the dial indicator is arranged to nt the mold extension collar.

2.5 lndicators- Two dial indicators; each indicator shall have a l in. (25 mm) throw and read to0.001 in. (0.02 mm).

2.6 Surcharge Weights-One annular metal weight with a center bale 2-118 in. (54.0 mm) indiameter and several slotted or split metal weights, all 5.718 in. (149.2 mm) in diameter and eachweighing 5 IO.lO lb. (2.27 IO.04 kg) <Fig. 1) (Note 2).

NOTE 2-when using split weighls. Ihe mass of the pair shall 6e S + 0.10 lb (2.27 + 0.04 kg.)

2.7 Penetrarían Piston-A metal piston of circular cross-section having a diameter of 1.954 .I.0.005 in. (49.63 IO.13 mm) (afea = 3 in.',1935 mm') and not less Iban 4 in. (102 mm) long. (See Fig.l.)

2.8 Loading Device-A compression-type apparatus capable of applying a uniformly increasingload up ,to 10,000 lb (44.5N) at arate of 0.05 in. (1.3 mm) per min., used to force the penetrationpiston joto the specimen.

2.9 Soaking Tank-A soaking tank suitable for maintaining the water level l in. (25 mm) abovethe top of the specimens.

2.10 Drying Oven-A thermostatically controlled drying oyen capable of maintaining a temper.ature of 110 I5 e (230 I9 F) for drying moisture samples.

2.11 Miscellaneous-Miscellaneous tools such as mixing pans, spoons, straightedge, fillerpaper, balances, etc.

Tl93 METHODS OF SAMPLlNG AND TESTlNG 677

3. SAMPLE

3.1 Prepare a sample in accordance with AASHTO T 99 (Method C) except that it shall weigh75 lb. (35 kg) or more. Material passing tire 50.00 mm (2 in.) sieve and retained on the 19.0 mm (3/4 in.)sieve shall be replaced with material passing the 19.0 mm sieve and retained on the 4.75 mm (No. 4)sieve as explained in the above AASHTO method. Select a representative portion weighingapproximately 25 lb. (11 kg) for a moisture-density test and divide the remainder of the sample toobtain 3 representative portions weighing approximatlly 1S lb. (6.8 kg) each.

4. MOISTURE.DENSITY RELATION

4.1 Using the 25 lb. (11 kg) 'partion, determine the optimum moisture content and maximumdry density in accordance with AASHTO T 99 (Method D).

S. PROCEDURE

5.1 Normally, 3 specimens must be compacted so that their compacted densities range from 95percent (or lower) to 100 percent (or higher) of the maximum dry density determined in Section 4. /

NOTEJ-Generally about 10.30. and 65 blows per layer are suitable for eompacting specimens 1. 2. and 3 respectivelyo More than 56blows per layer are generally required to mold a CBR specimen to 100 pereent ofthe maxiOlum dry deosity deterOline~ by AASHTO T 99(Melhod DI; Ihis is due lo the sample fo.oIhe moislure-densily test being reused. while the sample for Ihe CBR specimen is mixed andcompaeted only ancl'o

NOTE 4-50me laboratories may prefer to test only one specimeo. whieh would be compacted to maxiOlum dry density at optimummoisture cootent as determioed by AA5HTO T 990

5.2 Clamp the mold to the base plate. attach the extension collar and weigh to the nearest 0.01lb. (S g). Insert the spacer disk into the molp and place a coarse filler paper on top of the disk.

5.3 Mix each of the three l S lb. (6.8 kg) p6rtions prepared in 3.1 with sufficient water to obtainthe optimum moisture content determined in Section 4.

5.4 Compact one of the portions of soil-water mixture into the mold in 3 equal layers to give atotal compacted depth of about 5 in. (127 mm) compacting each layer with the lowest selected number01"blows in arder to give a compacted density of 95 percent or less of the maximum density.

5.5 Determine the moisture content of the material being compacted at the beginning and endof the compaction procedure (2 samples). Each moisture sample shall weigh at least 100 g for fine-grained soils and 500 g for coarse-grained soils.

5.6 Remove the extension collar. and using a straightedge, trim the compacted soil even with thetop of the mold. Surface irregularities should be patched with small-sized material. Remove the spacerdisk. place a coarse filter paper on the perforated base plate. invert the mold and compacted soil andplace on the filler paper so the compacted soil is in contact with the filler paper. Clamp the perforatedbase plate to the mold and attach the collar. Weigh the mold and specimen to the nearest 0.01 lb. (S g).

5.7 Compact the other two 1S lb. (6.8 kg) portions in accordance with the procedure in 5.4through 5.6. except that an intermediateo number 01"blows per layer should be used to compact thesecond specimen and the highest number 01"blows per layer shall be used to compact the third speci-mello

6. SOAKING

6.1 Place the swell plate with adjustable stem on the soil sample in the mold and apply ?ufficientánnular weights to produce an intensity of loading equal to the mass of the subbase and base coursesand surfacing above the tested material,.i:c5 lb. (2.26 kg) but in no case shall the mass be less than 10lb. (4.54 kg).

6.2 Place the tripod with dial inditator on top of the mold and make an initial dial reading.6.3 Immerse the mold in water to allow free access of water to top and bottom of the specimen.

During soaking. maintain the water 1e"velin the mold and the soaking tan k approximately 1.0 in (25.4film) above the top of the specimen. Soak the specimen 96 h (4 days).

NOTES-A shorterimme"iol1period(ootlessthan 24h) maybe usedfur soil-aggregatematerialsthat drain readilyir testsshuwthatthe shorter period does not affect the test resultso For some day satis. a soaking period greater than 4 days Olay be requiredo

678 METHOOS OF SAMPLlNG ANO TESTING TI93

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TABLE OF MEASUREMENTS

FlCURE I - Califcrnia Bearino Ralia Tes! AQPluotus

TRIPOO FOR OETERMINING EXPANSION SURCHARGE SPACER01$(

MATERIAL STEEI."'.. SfEa.-DIMENSION A B C O E F G H 1 J K L o M. N. P

METRIC, mm. 6.3 IV 63.5 120.6 9.6 1.5 152.4 190.5 76.2 95.2. 19.0 54.0 149.2. 150.' 61.4

TOlERA NCE. mIno 0.1 O."ENGLISH in.. 1/4 1/2. 2. 1/2. 4 314 3/8 1/16 6 71/2 3 33/4 3/4 21/8 57/8 515/16 lA"

TOLERANCE in. 1/3l O.OO

MOlO WITH EXTENSION COLLAR PISTONMATERiAl STEEL."" STEEL.""

DIMfNSION A E F G" P Q T" U" V" w Ixl y ! A R S'

METRIC, mIli. 6.3 9.5 1.6 152.4117.8 61.4 88.9 158.0238.1 165.1 212..7123.8 I 33.3 50.8 6.3 69.8 496

TOLERAI'iCE,mm. 0.66 041 0.13 I I 0.13

ENGlISH. in. 1/4 3/8 1/16 6 7 2.416 3 '/2 67/32 9 3/8 6 1/2. 8 3/8115116 1 5{16 2 1/4 3/4 1.954

TOLERANCE ,in. 0026 0.(,16 005 I 0.005

AOJUSTABlE STEM AltO PlATEMATERIAL . EiRONZE

DlMENSION a b e d e. f g h k m n. p' , s t

METRIC., mm. 11.12 11.11 5.6 11.9 3.2 46.04 50.8 69.8 75.4 19.0 28.6 9.5 6.3 107.9 1492

lOL.ERANCE. mm.eo" 0.0"0'000 .oooa

ENGLISH, in. 378 375 7/32 15/32 119 113/16 2 23/4 23VJ2 314 1 1/8 3/8 1/4 4 V4 7/e

TOlERANCE ,in..ooos oos.coao J)Coo

Tl93 METHODS OF SAMPLlNG AND TESTING 679

6.4 At the end 01'96 h, make a final dial reading on the soaked specimens and calculate theswell as a percentage 01'the initial sample length:

P 1I - Change in lengt!>in in. during soaking X 100ercent swe - 4.584 in.

6.5 Remove the specimens from the soaking tank, pour the water off the top and allow to draindownward for 1S mino Cate shall be taken not to disturb the surface of the specimens during removal01' the water. After draining, remove the surcharge weights and perforated plates.

NOTE ó- The specimens may be weighed after draining when it is desired to determine the average wet density 01' the soaked anodrained material.

7. PENETRA TION TEST

7.1 Application o( Surcharge-Place a surcharge of annular and slotted weights on thespecimens equal to that used during soaking. To prevent displacement 01'soft materials into the hole ofthe surcharge weights, seat the penetration piston after one surcharge weight has been placed on thespecimen. After seating the penetration piston the remainder 01'the surcharge weights shall then beplaced around the piston.

7.2 Seatillg Piston-Seat the penetration piston with a 10 lb (4.54 kg) load, th.:n set both thepenetration dial indicator and the load indicator to zero.

7.3 Application q(Load-Apply the loads to the penetration piston so the cate oí' penetration isuniform al 0.05 in. (t.3 mm) per mino Record the load when the penetration is 0.025, 0.050, 0.075,0.100,0.150,0.200 and 0.300 in. (0.64,1.27,1.91,2.54,5.08, and 7.62 mm). Load readings atpenetrations 01'0.400 and 0.500 in. (t 0.16 and 12.70 mm) may be obtained if desired.

NOTE7- The moisture content of the upper 1.0 in. (25 mm) may be determined after testing if desired. Moisture samples shall weighat least 100 g for fine-grained soils and 500 g for granular soils.

8. CALCULATIONS

8.1 Stress-Strain Cun'e-Plot the stress-strain (resistance to penetration-depth 01' penetration)

curve ror each specimen as shown in Fig. 2. In so me instances, the initial penetration t;.akes placewithout a proportional inerease in the resistanee to penetration and the eurve may be eoneave upward.To oblain the true stress-strain relationships, correet the eurve having eoneave upward shape near the

origin by adjusting the location 01' the origin by extending the straightline portion 01' the stress-straincurve downward until it intereseets the abscissa. (See dashed lines).

8.2 Cali(omia Bearing Ratio- The eorreeted load values shall be determined for each specimenal 0.10 and 0.20 in. (2.54 and 5.08 mm) penetration. California Bearing Ratio values are obtained in

pereent by dividing the eorreeted load values at 0.10 and 0.20 in. (2.54 and 5.08 mm) by the standardloads 01' 1000 and 1500 psi (6.9 and 10.3 MPa) respeetively, and muItiplying these ratios by 100.

CBR = Correctedload valueX 100Sw11llard Load

8.2.1 The CBR is generally seleeted at 0.10 in (2.54 mm) penetration. 11'the ratio at 0.20 in.(5.08 mm) penetration is greater, the test shall be rerun. If the check test gives a similar result, the ratioat 0.20 in. (5.08 mm) penetration shall be used.

8.3 Using the data obtained from the 3 specimens, plot the CBR-Dry Uensity as Moldedrelation as shown in Fig. 3. The design CBR may then be determined at the desired percentage 01'themaximum dry density, normally the minimum pereentage eompaetion permitted by the ageney'seompaetion specifieations.

9. REPORT

9.19.1.19.1J9.1.3

The report shall include the following information for eaeh specimen:Compaetion effort (number 01' blows per layer)Drydensityasmolded petoMoistureeontentasmolded pct.

680 METHOOS OF SAMPLING ANO TESTING TI93

9.1.4 Swe1T(pereentoforiginallength) peto9.1.5 CaliforniaBearingRatio pe!.

100

100

CORRECTEO LOAO VALUESAT O;Z IN. PENETRATION

500

..LI~ 400~e::...z~ 300o..wgz: 200.-;tw.

CORRECTED LOAD VALUESAT 0.1 IN. PENETRATlON

~2 .

AOJUSTEO ORIGINS FOA CONCAVE-UPWAROSHAPE OF CURVES

0.2 0.3 0.4'ENETRATlON-INCHES

FIG. 2.-Correction 01 Stre88-Strain Curvell.

O.S

Tl93 METHODS OF SAMPLlNG ANO TESTlNG 681

125

«CD 75o

o...~c(o ~Oel)

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.10 BLOWS PER LAYER

I

100

25

o100 .105 110 ~15 120

DRV DENSITV AS MOlDED- PCF125 130

EXAMPUGIVEN: MAXIMUIIDRYD!NSITY 8Y TOI-&1(IIETHOO 01-124 P.C.~FINO: THE C 8" AT 05 PE RCENT Of THE AIOVE MAXIMUIIDR"( DINany.SOLUTION: e5 PERCENT Of 124 P.C.f.. 117.8 P.C.'.

AT 117.8 P.O.'. TH! C 8 R IS 51

FIG. 3.-Dry DenBÍty VeTBu8 e B R