- 1 - California Test 304 STATE OF CALIFORNIA— BUSINESS, TRANSPORTATION AND HOUSING AGENCY December 1999 DEPARTMENT OF TRANSPORTATION ENGINEERING SERVICE CENTER Transportation Laboratory 5900 Folsom Blvd. Sacramento, California 95819-4612 METHOD OF PREPARATION OF BITUMINOUS MIXTURES FOR TESTING CAUTION: Prior to handling test materials, performing equipment setups, and/or conducting this method, testers are required to read “ SAFETY AND HEALTH”in Section D of this method. It is the responsibility of the user of this method to consult and use departmental safety and health practices and determine the applicability of regulatory limitations before any testing is performed. A. OVERVIEW This method provides procedures for the preparation of bituminous mixtures for the following California Tests 303, 305, 307, 308, 310, 360, 366, and 367. The preparation procedures are for laboratory design mixtures, mixtures from the field for job control, and cores taken from the pavement for special studies. The procedures are presented in two parts. Part 1. Method of Preparation of Design Sets and Field Samples Prior to Compaction Part 2. Method of Compacting Bituminous Materials for Swell, Stability, Moisture Vapor Susceptibility and Specific Gravity Tests B. APPARATUS 1. Ovens, capable of maintaining temperatures up to 200 ± 5°C. 2. Oven, capable of maintaining a tempera- ture of 60 ± 3°C with provisions for free circulation of air throughout the oven. 3. One balance, 5-kg capacity, accurate to 1 g. 4. Sieves, Standard Sizes; 25 mm, 19 mm, 12.5 mm, 9.5 mm, 4.75 mm, 2.36 mm, 1.18 mm, 600 μm, 300 μm, 150 μm and 75 μm. 5. Sample splitter for aggregates – riffle type or equal. 6. Sample splitter for bituminous mixtures – rotating pan type (optional, see Figure 1). 7. Pans, approximately 250 mm diameter by 50 mm deep. 8. Pans, approximately 280 by 180 by 25 mm deep. 9. Pans, approximately 200 mm diameter by 45 mm deep. 10. Pans, approximately 305 mm diameter by 65 mm deep. 11. Thermometers, metal stems, with range of 35° to 260°C. 12. Metal scoop, No. 3. 13. Beakers, 800 mL. 14. Hot plate, approximately 300 by 450 mm (if hand mixing is employed). 15. Trowels, small pointed. 16. Mechanical mixing machine (optional, see Figure 2). 17. Gloves, heat resistant.
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California Test 304STATE OF CALIFORNIA— BUSINESS, TRANSPORTATION AND HOUSING AGENCY December 1999
DEPARTMENT OF TRANSPORTATIONENGINEERING SERVICE CENTERTransportation Laboratory5900 Folsom Blvd.Sacramento, California 95819-4612
METHOD OF PREPARATION OF BITUMINOUS MIXTURES FOR TESTING
CAUTION: Prior to handling test materials, performing equipment setups, and/or conducting thismethod, testers are required to read “SAFETY AND HEALTH” in Section D of this method.It is the responsibility of the user of this method to consult and use departmental safetyand health practices and determine the applicability of regulatory limitations before anytesting is performed.
A. OVERVIEW
This method provides procedures for thepreparation of bituminous mixtures for thefollowing California Tests 303, 305, 307, 308,310, 360, 366, and 367. The preparationprocedures are for laboratory design mixtures,mixtures from the field for job control, andcores taken from the pavement for specialstudies.
The procedures are presented in two parts.
Part 1. Method of Preparation of DesignSets and Field Samples Prior toCompaction
Part 2. Method of Compacting BituminousMaterials for Swell, Stability,Moisture Vapor Susceptibility andSpecific Gravity Tests
B. APPARATUS
1. Ovens, capable of maintainingtemperatures up to 200 ± 5°C.
2. Oven, capable of maintaining a tempera-ture of 60 ± 3°C with provisions for freecirculation of air throughout the oven.
3. One balance, 5-kg capacity, accurate to1 g.
4. Sieves, Standard Sizes; 25 mm, 19 mm,12.5 mm, 9.5 mm, 4.75 mm, 2.36 mm,
1.18 mm, 600 µm, 300 µm, 150 µm and75 µm.
5. Sample splitter for aggregates – riffle typeor equal.
6. Sample splitter for bituminous mixtures –rotating pan type (optional, see Figure 1).
7. Pans, approximately 250 mm diameter by50 mm deep.
8. Pans, approximately 280 by 180 by 25 mmdeep.
9. Pans, approximately 200 mm diameter by45 mm deep.
10. Pans, approximately 305 mm diameter by65 mm deep.
11. Thermometers, metal stems, with range of35° to 260°C.
12. Metal scoop, No. 3.
13. Beakers, 800 mL.
14. Hot plate, approximately 300 by 450 mm (ifhand mixing is employed).
The temperature of the asphalt at the timeof mixing shall closely approximate theaggregate temperature, and in no instanceexceed 190°C.
2. Laboratory mixtures employing liquidasphalts are not governed by a mixingtemperature. The liquid asphalt is added tothe unheated aggregate at the minimumtemperature that will permit ready pouring.The heat produced by the mixing machine,or hot plate if hand mixed, shall besufficient to obtain a satisfactory mixture.Care shall be exercised not to overheat themixture when using a hot plate for mixing.
3. An acceptable mechanical mixer is shownin Figure 2. It consists of steel bowlshaving hemispherical shaped bottoms, intowhich mechanically-driven stirring paddlesare inserted. The paddle is shaped to fitthe bottom of the bowl and is rotatedat 3.1 ± 0.2 rad/s. Spring steel bafflessupplement the paddle to aid in theagitation of the mixture.
Preheat the aggregate and asphalt to therequired mixing temperature prior toplacing them in the mixer. Maintain thetemperature during the mixing period withsupplemental heat such as infrared lampsfocused on the bottom of the mixing bowls.The length of mixing time varies with thetype of aggregate. For instance, typicalnonabsorptive aggregates require from 3 to5 min mixing, while the more absorptivematerials will require correspondinglylonger periods of mixing.
D. SAFETY AND HEALTH
Personnel should use heat resistant gloveswhen working with hot materials. Use properlifting techniques when handling bags ofaggregate. Reasonable care should beexercised to avoid being burned by hot asphalt,aggregate or equipment.
Caution must be exercised in the operation ofthe compactor to prevent any object, other thanthe sample itself, from interceding between thecompactor foot and the mold at any time whilethe ram is in motion. The clearance betweenthe edge of the mold and the compactor footis approximately 2 mm. The applied shearingforce exerted could cause severe injury to bodyextremities or damage to equipment.
Caution should also be exercised in theoperation of the testing machine to keep anyobjects other than the sample and testingapparatus clear of the loading head during thetesting operation.
Prior to sampling, handling materials or testing,Caltrans personnel are required to readSections 2.2, 4.1, 5.1 and 5.3 of CaltransLaboratory Safety Manual and the MaterialsSafety Data Sheets (MSDS) for all materialsused. Users of this method do so at their ownrisk.
PART 1: METHOD OF PREPARATION OFDESIGN SETS AND FIELD SAMPLESPRIOR TO COMPACTION
A. PREPARATION OF DESIGN SETS
1. Aggregate
Refer to Item A.4 for special gradingsrequiring aggregates larger than 25 mm.
a. Aggregate samples from bins: Thesesamples represent aggregate after allprocessing has been completed; i.e.,just prior to addition of the bitumen.Thus, test these samples in as near the“as received” condition as possible.
Separate the sample on the coarseaggregate sieves according toCalifornia Test 202. This separationshould be done by hand if theaggregates are coated to prevent
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removal of these coatings. Use thisgrading and combine proportionalamounts to make test samples of thevarious sieve size fractions.
b. Aggregate samples from stockpiles:Treat stockpile samples in the samemanner as bin samples, provided therewill be no further processing prior tothe addition of bitumen.
c. Aggregate from pits or quarries. Pitor quarry preliminary samples areprocessed in various manners.Normally, instructions will be furnishedby the sampler as to whether theoversize material is to be crushed ordiscarded. If crushing is to beemployed, scalp the material on thedesignated sieve size and crush theretained material in such a manner thatwhen blended back with its naturalcomponent, it will conform to thegrading requirements for the project.Using procedures outlinedin California Test 201, remove thecoatings from the coated coarseaggregates and reduce soil lumps topassing the 4.75 mm. This isnecessary in order that all the finematerial will be accounted for in thesieve analysis and included in thesample when tested.
d. Use the sieve analysis of the sample orsamples and design the mix to conformto the specified grading limits byblending or adjusting. Designing to asmooth grading curve approximatingthe middle of a specified range isdesirable but not always essential.General practice is to produce the mostuniform grading possible within thespecification limits with the material onhand. Scalping out oversize, wastingportions, and combining are methodsused to attain a desired grading. Allfinal gradings shall be based upon awash sieve analysis.
e. Samples of aggregate which are toconform to a specific gradingrequirement and fail to do so oncertain sieve sizes can, in manycases, be adjusted to conform to thegrading requirement by wasting
certain portions of the sample. Anyadjustment of grading shall be suchthat it can be duplicated underactual field conditions. Computationsand examples for these adjustmentsare given in California Test 105.
f. The procedure for blending two ormore individual samples incombination to produce a final gradingconformingto certain requirements consists ofcalculations using various percentagesof each in combination until asatisfactory grading is produced. Asgrading limits are based on materialsof uniform specific gravity, a correctionshould be made to compensate for anydifferences of 0.20 or more in thespecific gravity of the individualsamples used in the blend. This alsoapplies to the final gradation if adifference between the coarse and finefraction is 0.20 or more.
To make this correction for specificgravity, design the mix first in the usualmanner without regard for the specificgravities of the aggregates. This willgive the desired by-mass grading. Toobtain the percent by volume, followthe procedure in the “C” portion ofCalifornia Test 105.
g. The cumulative mass required for the1000 g and 1200 g specimens normallyused are derived by multiplyingcumulative percent as used (fromthe grading of the aggregate) by 10 or12 for the 1000 g or 1200 g sample,respectively. In cases whenadjustment of the grading is necessary,the cumulative mass is based on theadjusted grading.
An example of the computationrequired is shown below:
Sieve Size, mm Percent Passing25.0 10019.0 899.5 784.75 67
The cumulative mass for the samplesare obtained as follows:
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Pass Ret. 1000 g Sample 1200 g Sample25.0 19.0 (100-89) X 10 = 110 (100-89) X 12 = 13219.0 9.5 (100-78) X 10 = 220 (100-78) X 12 = 2649.5 4.75 (100-67) X 10 = 330 (100-67) X 12 = 3964.75 (100-0) X 10 = 1000 (100-0) X 12 = 1200
The use of cumulative mass isconsidered the preferable method ofcombining the various sizecomponents of aggregates forbituminous mix tests; however, theindividual increments may be weighedseparately and combined if desired.
h. The material that is weighed out for thetest specimens shall be free frommoisture. Thoroughly quarter thepassing 4.75 mm sample portion, andplace it in pans approximately 250 mmin diameter by 50 mm deep. Do notadd the passing 4.75 mm material fromthe sample sack without quartering orsplitting as segregation may occur.
The dry mass of the aggregate for theswell specimen shall always be 1000 g.Normally, a 1200 g dry mass issufficient for the stabilometerspecimen. However, if the averagespecific gravity of the aggregate is 2.80or higher, a 1300 g dry mass isgenerally required for the stabilometerspecimen. Use the computed mass toprepare the specimens. Normally thenumber of specimens required per setconsists of two for the swell test, fourfor the stabilometer test, and two forthe MVS test. Weigh all material to thenearest gram.
i. Proportioning aggregate for centrifugekerosene equivalent (CKE) test(California Test 303).
(1) Passing 4.75 mm material fordetermination of Kf. Assume thatsamples A, B, and C are to becombined.
Let:a = Percent passing 4.75 mm for
Sample A
b = Percent passing 4.75 mm for Sample B
c = Percent passing 4.75 mm for Sample C
Then the mass in grams of passing4.75 mm material for each sampleneeded to give a total representativesample of 100 g is determined by thefollowing formulas:
Xa = [a/(a+b+c)] x 100
Xb = [b/(a+b+c)] x 100
Xc = [c/(a+b+c)] x 100
If it is desired to have extra material,as for instance, 5 g to allow for loss ofweight in drying, then substitute 105 for100 in the above formulas.
(2) Coarse material for determinationof Kc. Determine the percent ofpass 9.5 mm, retained 4.75 mmmaterial for each sample andcombine as above.
2. Bitumen
a. Use bitumen that is proposed for theproject (both grade and source).
b. Determine “K” values. Refer toCalifornia Test 303, “CentrifugeKerosene Equivalent. ”
c. Determine the approximate bitumenratio. Refer to Figure 4, “ApproximateBitumen Ratio,” of California Test 303.
d. On nonabsorptive material, fourstabilometer specimens are sufficientfor evaluating a sample. Generalpractice is to prepare one specimenwith the amount of asphalt asdetermined by the CKE test, two aboveCKE, in 0.5 % increments, and one0.5 % below the CKE amount. The0.5 % increment is satisfactory for themajority of samples; however, forextremely critical mixtures, theincrements should be lowered to 0.3 %and the number of specimensincreased to five. For highlyabsorptive, noncritical mixes, increasethe increment to 1.0 % and use morespecimens as necessary. In any case,the test series should have at least one
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specimen with an excess of asphalt asmanifested by moderate or heavyflushing after compaction.
e. Refer to California Test 367 andestablish the Optimum BitumenContent (OBC).
f. Prepare the swell and moisture vaporsusceptibility test specimens induplicate using the OBC.
g. For open graded mixtures, prepare a1000 g sample for inspection, using thebitumen content obtained fromCalifornia Test 368.
3. Mixing and Curing
a. Preheat the aggregate if necessary tocomply with temperatures listed in C,“Mixing.” Add the proper amount ofasphalt to the aggregate (e.g., OBC- 0.5 %, OBC, OBC + 0.5 %, etc.).
b. The mixing may then be performed byone of the following two methods:
(1) Transfer the mixture to a suitablepan, and place pan on a hotplate to maintain the mixingtemperature. Hand mixvigorously with a small pointedtrowel until all particles arecoated. Mix aggregates that donot require preheating at thelowest possible temperature.
(2) Where the volume of worknecessitates mass productionmethods, a mechanically operatedmixer may be preferred.
c. When mixing is completed, transfer themix to a suitable flat pan,approximately 280 by 180 by 25 mmand cure at a temperature of 60 ± 3°Cin an oven equipped with air circulationfor 15 to 18 h.
d. The mixture is then ready for thecompaction procedure as described inPart 2.
4. Samples in which aggregate larger than25 mm is to be used in mixture.
a. Preliminary or design samples.
(1) Design the grading to conform tothe specified limits.
(2) Calculate the surface area andperform the CKE test inaccordance with CaliforniaTest 303.
(3) In preparing test samples prior toadding the asphalt binder, use theentire grading up to and includingthe maximum size specified.
(4) Mix the amount of asphaltindicated by the CKE test with aspecimen and provide additionalspecimens covering the rangeabove the below the amountdetermined by the CKE test in0.5% increments.
(5) Cure the mixtures in the normalmanner.
(6) For the swell, stabilometer andMVS tests, screen the test samplethrough a 25 mm sieve anddiscard all retained material. Themass of the total test sample priorto screening on the 25 mm sieveshould be sufficient to provideenough minus 25 mm material toform the usual 63.5 mm highbriquette for the stabilometer test.Base the final recommendedasphalt content for the entiremixture to be used on the projecton the results and informationfurnished by the tests performedon the minus 25 mm portion of themixture. Do not attempt to makeallowances for the retained25 mm portion.
(7) For the specific gravity test,use the entire grading. Batchenough material to obtain 152 mmdiameter by 100 mm highspecimens.
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B. PREPARATION OF FIELD SAMPLES
1. For samples of uncompacted dense-gradedasphalt concrete with a paving gradeasphalt, heat the sample to approximately95°C for workability. Thoroughly mix andquarter the sample, either by mechanical orhand quartering method, into amountsneeded for the following tests:
1-Stabilometer 1200 - 1400 g1-Moisture Vapor Susceptibility 1200 - 1400 g1-Swell 1100 g1-Extraction (California Test 310) 650 - 800 g3-Surface Abrasions 1100 g each
Place the material for the above tests thatrequire compaction (the extraction samplesmay be immediately placed in theextraction thimble and tested) in suitableflat pans, approximately 280 by 180 by25 mm, and cure at 60 ± 3°C for aminimum period of 15 h in an oven withprovision for air circulation. The samplesare then ready for compaction as describedin Part 2.
2. Samples of uncompacted dense-gradedasphalt concrete with liquid asphalt shouldbe received in a sealed container. DONOT HEAT. Thoroughly mix and quarterthe sample either by mechanical or handquartering method into the amountsneeded for the following tests:
2-Stabilometer 1200 - 1400 g each1-Moisture Vapor Susceptibility 1200 - 1400 g1-Swell 1100 g1-Extraction (California Test 310) 650 - 800 g1-Moisture 500 g
Immediately place one stabilometersample and a moisture sample in separatesealed containers until ready for testing,then test without curing or additionalprocessing. Place the material for theremaining tests that require compaction insuitable approximately 280 by 180 by25 mm flat pans (the extraction samplemay be placed immediately in anextraction thimble and tested) and cure at60 ± 3°C for a minimum period of 15 h inan oven with provision for air circulation.The samples are then ready forcompaction. Report data from both “asreceived” (uncured) specimens, and curedspecimens, on the same report.
3. Samples of uncompacted dense-gradedasphalt concrete with aggregate larger than25 mm.
a. Quarter the sample and prepare testspecimens in accordance withinstructions above relating to type ofasphalt used in the mixture. Prepare a2000-g extraction sample and a 2700 gspecific gravity sample.
b. After quartering, screen through a25 mm sieve and use only the passingportion for all tests except theextraction and specific gravity tests.
c. Be sure that the samples for extractionand sieve analysis and for specificgravity are representative of thecomplete mixture as placed in theroadway.
d. Divide the 2000-g extraction sampleinto three approximately equal parts forthe test (California Test 310).
e. After extracting the three portions,calculate the asphalt content basedupon the mass for the total sample asone asphalt content.
4. Samples of compacted dense-gradedasphalt concrete. Compacted samplesusually consist of 200 by 200 mm slabs or101.6 mm diameter cores that have beencut from the pavement. Compactedsamples to be tested for stability or specificgravity should be shipped and stored on asand bed to maintain integrity prior totesting. They should be dried at 38°C for48 to 72 h before obtaining a specificgravity determination.
a. Slabs: Saw the slab to obtain a 1000to 3000 g mass for the specific gravitytest.
Do not cut the sample with a chisel asthis may alter the integrity and providean erroneous value.
To minimize the effects of the sawnsample on the grading, heat asubstantial mass to 110 ± 10°C andsplit or quarter this material to obtain
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650 to 800 g for an extraction andsieve analysis.
b. Cores: Cores 101.6 mm in diametermay be tested at 60°C or lessertemperatures for stability.Temperatures exceeding 60°C,however, may cause damage to thecore and should be avoided. For coresin excess of 63.5 mm in height, trimthe core with a diamond saw to a63.5 mm height for the stabilometertest. Use plaster of Paris to cap andpatch obvious surface irregularities inthe core before testing for stability.
PART 2. METHOD OF COMPACTINGBITUMINOUS MATERIALS FORSWELL, STABILITY, MOISTUREVAPOR SUSCEPTIBILITY ANDSPECIFIC GRAVITY TESTS.
A. APPARATUS
1. Mechanical compactor, as shown inFigure 3, designed to consolidate thematerial by a series of individual or roving“kneading action” impressions made by aram having a face shaped as a sector of a101.6 mm diameter circle. The compactormust be capable of exerting a force of7120 N (3.45 MPa pressure by the tamperfoot).
2. Compactor accessories: 101.6 ± 0.13 mminside diameter by 127 ± 2 mm-high steelmolds, a mold holder, and 101 ± 1 mmdiameter cardboard disks.
3. Testing machine, 220 kN capacity.
4. Metal followers (two): one101.2 ± 0.13 mm outside diameter by140 ± 6 mm high, and the other ram101.2 ± 0.13 mm outside diameter by40 ± 6 mm high.
5. Two ovens to maintain temperaturesof 60 ± 3°C and 110 ± 5°C, respectively.
6. Mechanical spader (optional), designed toprevent segregation of coarse and finematerial or the formation of rock pockets inthe test specimen by introducing themixture into the compaction mold from an
endless belt at the same time imparting aspading action with four mechanicallyoperated 12.7 mm diameter by 580 mm-long, bullet-nosed steel rods. See Figure4.
7. Special feeder trough, 100 mm wide and400 mm long, that may be used in lieu ofthe mechanical spader. See Figure 5.
8. Flat metal scoop, approximately 250 by360 mm.
9. 12.5 mm sieve.
10. Special pressing standard for applyingaluminum seal caps. See Figure 6.(Dimensions shown are in mm.)
11. Aluminum seal caps, 100.0 ± 0.5 mmdiameter by approximately 1 mm thick.
12. Balance, 2000-g capacity, 1 g accuracy.
13. Suitable device for measuring height oftest specimens to the nearest 0.1 mm.
14. Metal disc, 100 ± 1 mm diameter by12 mm thick minimum. (For asphalt rubberspecimens only.)
For large stone mixes, the following apparatuswill be required:
1. Tamper foot, approximately 3.48 x 10-3 m2.
2. Compaction molds, 152.4 ± 1 mm diameterby 203 ± 1 mm high.
3. Pressing ram, 151 ± 1 mm diameter by127 ± 5 mm.
4. Mold holder.
5. 152 mm specimen extractor.
6. Mechanical compactor, capable of exertinga force of 12 kN (3.45 MPa pressure by thetamper foot).
B. FABRICATION
1. Swell test specimen.
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a. Prepare the mold by placing a paraffinimpregnated strip of ordinary wrappingpaper 19 mm wide around the inside ofthe mold, so that the bottom of the stripis 12 to 19 mm from the bottom of themold. Dip the paper strip in hotparaffin and apply while hot to theinside of the room temperature mold.
b. Place the mold in the mold holder. Putthis unit into position in the mechanicalspader. (If a mechanical spader is notavailable, proceed to paragraph “h”).Place a metal shim 6 mm thick,approximately 19 mm wide by 65 mmlong under the mold adjacent to theportion of the mold holder that extendsup into the mold. Place the 100 mmdiameter cardboard disk into the moldon top of the mold holder base.
c. Weigh out 1000 ± 1 g of mix that hasbeen brought to the proper compactiontemperature:
60 ± 3°C for mixtures containingliquid grade asphalt.
110 ± 5°C for mixtures containingpaving grade asphalt.
Room temperature for mixturescontaining liquid grade asphaltswhen it is desired to test withwhatever moisture may be presentin the sample.
d. Separate the coarse and fine materialby screening the mix through a12.5 mm sieve onto the flat metalscoop.
e. Arrange the separated material into twoparallel rows across the width of thescoop.
f. Slide the mix onto the feeder belt ofthe mechanical spader, exercising careso as not to disturb the sizearrangement affected on the metalscoop.
g. Start the mechanical spader anddistribute all of the material into thecompaction mold.
h. In lieu of the mechanical spaderdescribed above, a speciallyconstructed feeder trough, approxi-mately 100 mm wide by 400 mm long,may be used to place the mix into themold. See Figure 5. Thoroughly mixand disperse the heated material onthe trough (which has also beenpreheated to approximately thecompaction temperature to be used) toensure a uniform sample whentransferred to the mold. Place themold in position in the mold holder andplace a 100 mm diameter cardboarddisc into the mold on top of the moldholder base.
Use a paddle, shaped to fit the trough,to push one half of the material into themold. Rod the material 20 times in thecenter of the mass and 20 timesaround the edge with a bullet-nosedsteel rod 9.5 mm in diameter, by400 mm long. Then, push theremainder of the sample into the moldand repeat the rodding procedure justpenetrating the first lift. Perform theseoperations as rapidly as possible toprevent cooling of the sample. If twofeeder troughs and two mold holdersare available, the work can beexpedited by preparing another samplewhile one is being compacted. Theextra trough containing the sample iskept in the oven until ready forcompaction.
i. Place the mold holder containing themix and the mold into position in themechanical compactor.
j. Start the compactor and adjust the airpressure to a point where 1.7 MPa willbe exerted by the tamper foot. Keepthe tamper foot hot enough to preventthe mix from adhering to it.
k. Apply approximately 20 tamping blowsat 1.7 MPa to accomplish a semi-compacted condition of the mixso it will not be unduly disturbedwhen the full load is applied.The exact number of blows toaccomplish the semi-compaction shallbe determined by observation. Thenumber of blows may vary between 10
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and 50, depending upon the type ofmaterial, and in some instances wheresandy or unstable material is to becompacted, it may not be possible toaccomplish the compaction in themechanical compactor because ofexcessive movement of the mixtureunder the compactor foot. In theseinstances, apply a 178 kN compressionload at a speed of 6.35 ± 0.02 mm/minby the double plunger method, in whicha free-fitting plunger is placed belowthe sample as well as on top, tocomplete the compaction. Whencompacting the first specimen of a set,which is normally one of the swell testspecimens, if it is found that thematerial will not consolidate under thefull tamper load, subject the remainingspecimens in the set to a 178 kNcompression load only.1
l. Remove the 6 mm shim and releasethe tightening screw sufficiently toallow approximately 3 mm lateral sidemovement during the compactionstroke. Then raise the compactionpressure to 3.4 MPa and apply 150tamping blows to complete thecompaction in the mechanicalcompactor.
m. Remove the mold and specimen fromthe compactor and push the testspecimen to the opposite end of thecompaction mold. This is done toprovide water contact to the face of thespecimen that has not been in contactwith the compactor foot for the swelltest.
n. Apply a leveling-off load of 56 kN inthe testing machine1 at a head speedof 6.4 ± 0.05 mm/min with the bottomof the sample in contact with the lowerplaten of the press. Release theapplied load immediately.
o. Measure the height of the testspecimen to the nearest 0.1 mm andrecord for later use.
1 If the testing machine had a spherically seated type of upperhead, use the proper shims to lock it in such a manner that thecontact face is fixed firmly in a horizontal plane.
p. Let the compacted swell specimensremain at room temperature forapproximately 1 h prior to the start ofthe swell test.
q. Test according to California Test 305.
2. Stability test specimen. The steps used inthe fabrication of these test specimens arethe same as for the swell test specimenexcept for the following variations:
a. Use the amount of mix required toproduce a test specimen 63.5 mmhigh. This amount may be calculatedfrom the height that was recorded forthe 1000 g of material used for theswell test specimen by the followingformula:
(X/63.5) = 1000/Hor
X = (63 500/H)
Where:
X = Mass of mix in grams to give a63.5 mm-high specimen
H = Height in mm of the 1000 g swellspecimen
Example:
If 1000 g of mix gives a height of55.8 mm, what mass will be needed fora 63.5 mm high specimen?
X = (63 500/55.8) = 1138 g
b. Preheat the compaction molds andfeeder trough to approximately thecompaction temperature specifiedunder Part 2, B.1.c. [150 ± 5°C formixtures containing asphalt rubber].Paraffin strips are not used.
c. After compaction in the mechanicalcompactor, place the asphalt rubberspecimens on the metal disc to preventdistortion while cooling in the 60°Coven. Place the bituminous mixspecimens in the 60°C oven for thefollowing minimum length of time priorto applying a 56 kN leveling-off load:
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1 h if compacted at 60°C1-1/2 h if compacted at 110°C2 h if compacted at 150°C
Do not push the specimens to theopposite end of mold as is done in theswell test.
d. Apply the 56 kN leveling-off load1 bythe double plunger method in which afree-fitting plunger is placed below thesample as well as on top. Measure theheight of specimen to the nearest0.1 mm, record the measurement, andreturn the specimen to the 60°C ovento retain temperature for testing.
e. Compact road-mixed asphalt concretesamples at room temperature to retainthe moisture present. Select a time sothat the stability test may be performedimmediately following compaction. Ifthe stability test value is below thespecified value, repeat the test on amoisture-free sample compacted at60°C.
a. Fabricate the MVS test specimen thesame as the stability test specimenwith the following variations:
After heating as specified in paragraph2c, invert the mold and place on theMVS pressing standard, as shown inFigure 6. Press the specimen downthrough the mold until it seats on thepressing standard. Apply a 56 kNleveling off load1.
b. Test according to California Test 307.
4. Specific Gravity test specimen.
a. The specimens tested for stability areused to obtain specific gravities.
b. Large stone mixes.
1 If the testing machine has a spherically seated type of upperhead, use the proper shims to lock it in such a manner that thecontact face is fixed firmly in a horizontal plane.
(1) Using past experience and/orheight to mass ratios, determinethe mass needed to obtain a152 mm diameter by 100 mm highspecimen.
(2) Split the heated material intothree equal portions.
(3) Heat the mix and molds to110 ± 5°C.
(4) Place the mold in the mold holderon a 6 mm shim and insert a151 ± 1 mm diameter cardboarddisc into the mold on top of themold holder base.
(5) Place one portion of the mix intothe mold and systematically rodthe material 35 times with a bullet-nosed steel rod 9.5 ± 1 mm indiameter, approximately 400 mmlong.
(6) Place the remaining two portionsinto the mold at 110 ± 5°C,rodding each portion 35 times to adepth that just penetrates theprevious layer. Perform theseoperations as rapidly as possible.
(7) Place the mix assembly intoposition in the mechanicalcompactor.
(8) Compact the sample according toPart 2, B.1.j, k and l with thefollowing changes:
(a) If movement of the mixture isexcessive for compaction bythe compactor, reject this mixdesign. Do not apply acompression load using thetesting machine.
(b) After removing the 6 mmshim and releasing thetightening screw, raise thecompaction pressure to2.7 MPa instead of 3.4 MPaand apply 150 blows.
(9) Remove the mold from the moldholder, insert the pressing ram
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and immediately apply a 125.8 kNleveling load to the specimen.
(10) Allow the specimen to cool toroom temperature and push itfrom the mold.
(11) Observe and report any evidenceof flushing on the compactedsurface.
(12) Test according to California Test308, Method A.
C. PRECAUTIONS
1. To ensure proper particle orientation in thetest specimen, it is quite important that theoperator exercise particular care in placingthe mix on the feeder belt of themechanical spader or feeder trough.Indiscriminate screening and placing of themix may produce test specimens havingconsiderable segregation of the aggregatewith resulting inaccurate test results.
2. The compaction pressure shall bemaintained in accordance with the Methodof Operation and Calibration of theMechanical Compactor; see CaliforniaTest 101.
3. Compaction temperatures shall be carefullycontrolled.
4. Periodically check the 101.6 mm diametermolds. Do not use molds that becomeelliptical in excess of 101.6 ± 0.25 mm forstabilometer specimens.
