Chapter 2A
Designand Control of Hot-Mix Asphalt (HMA)MixturesUsingthe SuperpaveAsphaltMixtureDesignand Analysis System
1.General Scope
TheDepartment has established procedures forthe designandcontrol of hotHot-mix Mix asphalt Asphalt (HMA) based on theSuperpaveAsphalt MixtureDesignandAnalysis System. Superpave(Superior PerformingAsphaltPavements) is theend result of theStrategicHighwayResearchProgram’s (SHRP) $50millioninvestment in asphalt-related research. Unlike theempirical Marshall mixdesignsystem,Superpaveis a comprehensive method, based onperformancecharacterizationstailored specificallyto projecttraffic, environment, andstructuralsection. Since Superpaveconsiders theinteraction of traffic,climate,andpavementstructure within the pavingmix, the mixdesignandstructuraldesign aretrulybetterintegrated into a singlesystem. There arethreemain components to the system; theperformancegradedasphalt binderspecification, the Superpavevolumetricmixdesignprocedures, andtheadditional mixtestingandanalysis.Thepurposeof these procedures isto provide uniform guidancein theuse ofamore complexand currentlyincomplete,performance-relateddesignsystem for Department work.
Currently, the Superpaveasphaltbinderspecification and theSuperpavevolumetric mixdesignprocedures areavailableand will beusedbythe Department.Theadditional mixtestingand analysis is currentlynot readyforDepartment use. Nationally,the additional mixtestingand analysis is stillundergoing researchrefinements,validation work, and thedevelopment of performance models.Oncecompleted, the additional mixtestingandanalysis will provideperformance predictions ofmixturedesigns.Thesepredictionscan thenbeusedto enable the Department to specifyhot-mixasphaltpavements with greaterconfidence that the mix will performwellfor defined traffic andclimateconditions overrealistic and planned life cycles.
TheDepartment will follow theSuperpavemixdesign procedure andSuperpavespecifications contained in the StandardPractice forSuperpaveVolumetricDesignforHMA(AASHTO R 35) and Standard SpecificationforSuperpaveVolumetric MixDesign(AASHTO M 323)except as revisedherein. AllAASHTOstandard practices,specificationsand test procedures areimplied to reference themost currentapproved and published versionavailableat thetime ofproject bid letting.
2.DepartmentRevisions to AASHTOR35 -
StandardPractice forSuperpave Volumetric DesignforHMAAASHTO R35, Section 3. Terminology
ReviseSection 3 byadding newSubsections as follows:
3.14Durability-ameasureofresistance to disintegrationbyweather or trafficconditions. Themost importantfactorwith respect to durabilityis theamount ofbinder. An HMA mixtureis resistant to action ofairandwater in direct proportion tothe degree that theyarekept out of themix. It is desirable that themixshould contain
ashigh abindercontent as is consistent with balancedstrength,strain,andvoids for theexpected lifecycle of trafficload and environmental factors. This can beachieved withhighvoids Voids in themineral Mineral aggregate Aggregate (VMA). This will give thepavement maximumdurabilityandprevent ravelingbecause of adeficiencyof asphaltbinder. This bindercontent is referred toas the optimum.
3.15Flexibility-theabilityofthe HMA mixtureto bend repeatedlywithout crackingand to conform to changes in the base course.Tohave flexibility,amixmust containthe properamount of binder. Open-gradedmixturesare moreflexiblethandense-graded mixtures. Also, a mixture consistingof asofterbinder grade is moreflexiblethan thesamemixturemadewith a harder bindergrade.
3.16Workability-the propertythat enables the efficientplacement withoutsegregation,andcompaction of themixture.Harsh orstiffmixtures can result fromanexcess of coarse aggregate, low VMA, low binder content, or anexcess ofminus 75 m(No. 200)sievefraction.
3.17FrictionNumber-ameasureof thesliding force exerted on atirewhenavehicle’sbrakes arelocked. HMAwearingcourses must havethe highestpossiblefrictionnumber obtainablewith the combination of aggregates available inthe area.Thetype of coarseaggregate has thegreatesteffect on frictionnumber. Aggregateswhich polish rapidlyandrepeatedlyproducelow frictionnumbersbefore the normalservice lifeiscomplete should not be used.An excessivebindercontent can produceaflushedsurface resulting in low frictionnumber.
3.18SuperpaveGyratoryCompactor (SGC)-a mechanical compaction device usedto mold and compact 150mm (6 inch)diametermixturespecimens. It compacts thespecimens usingaloadingram which appliesaloadingpressureof 600kPato thespecimen. Themold is held at anangle during compaction.TheSGC gyrates thespecimen duringcompaction at a constantspeedof 30 revolutionsper minute.Thecompletetest procedureis found in AASHTOT 312.
3.19Initial numberof gyrations (Nini)-the number ofgyrationsappliedbytheSGCto themixturespecimensearlyin the compactionprocess and isgenerallyconsidereduseful in identifyingtender orpoorlygraded mixtures which maycompacttoo readilyormixtures that are too harshand require excessive compactiveeffort in the field.
3.20Design number of gyrations(Ndes) -the number of gyrations, whichwhenapplied to the design mixturespecimens, results in 4.0 percentair voids anddeterminesthe designasphalt content if NiniandNmaxrequirementsaresatisfied.Thiscompactionlevel is generallyconsidered to represent thepavements expectedair void contentseveralyearsafterconstruction,assumingthe correcttrafficlevelandclimate areaccountedforin design. It is also used to select the designasphaltcontent.
3.21Maximum numberof gyrations(Nmax) -the maximum number ofgyrationsappliedduringtheSGC compactioncycle and represents themaximum level themixisexpected to compact to in the pavement assuming the correcttraffic level and climateareaccountedforin design. Themaximum densityrequirementat Nmaxinsures that the
mixwill not compactexcessivelyunder thedesigntraffic,becomeplastic,and producepermanentdeformation. Theair voids content must be 2.0 percent orgreater.
AASHTO R35, Section 4. Summary ofthePractice
ReviseSubsection 4.1 byadding the following toNote3:
When usingRAPor manufacturer waste RecycledAsphaltShingles(RAS),theDepartment’smodifieddesignprocedures (SeeAppendixH)shall be followedexclusively.
ReviseSubsection 4.2 byadding the following toNote4:
Also, otherrecognizedproceduresmaybeusedtoselecttrialblends or recommend adesign aggregate structure.Onesuchmethod is the “BailyMethod forGradationSelection in Hot-MixAsphalt MixtureDesign,” byW.R. Vavrik, G. Huber, W.S. Pine,
S.H. Carpenterand R. Baily. TransportationResearchCircular E-C044, October2002.Copies maybeobtainedbycontactingNational Research Council, Business Office,500FifthStreet, N.W. Washington D.C. 20001. Tel: (202)334-3213 oremail publication is alsoavailableon theInternet at links for “OnlineDocuments” and“E-Circulars”and then locatingE-Circular44.
ReviseSubsection 4.4 completely as follows:
The moisture susceptibility of the design aggregate structure is evaluated at the design binder content: the mixture is conditioned according to In the first sentence, change the reference for how the mixture is conditioned from “mixture conditioning for the volumetric mixture design procedure in R 30” to “therevised mixtureconditioningfor volumetric mixture designand production qualitycontroltestingtime (AppendixIherein) plus an additional 2 hours, compacted to 7.0 +/- 0.5 percent air voids in accordance with T 312, and evaluated according to T 283.
All mixtures shall include either a compatible, heat stable, amine-based liquid anti-strip, hydrated lime or another compatible alternate anti-strip additive. Incorporate the anti-strip additive at least at the minimum dosage rate published on the anti-strip additive’s technical data sheet from the anti-strip manufacturer (typically 0.25% by mass of asphalt).
Mixtures that incorporate both coarse and fine aggregates classified as a type of Sandstone, Siltstone, Slag, Quartz, Shale, or Gravel shall include either a compatible, heat stable, amine-based liquid anti-strip, hydrated lime or another compatible alternate anti-strip additive incorporated at a dosage rate one level higher than the minimum recommended dosage rate recommended by the manufacturer (typically 0.50% by mass of the total asphalt).
The producer may elect to perform additional testing for mixtures that incorporate both coarse and fine aggregates classified as a type of Sandstone, Siltstone, Slag, Quartz, Shale, or Gravel with an anti-strip agent dosage rate one level higher than the minimum dosage rate recommended by the manufacturer compared to the test results that incorporate anti-striping agent at the minimum dosage rate. If all of the following bullet points are true design the JMF with the higher dosage rate.
- The TSR of the higher dosage mixture is greater than the TSR of minimum dosage mixture.
- The conditioned and unconditioned tensile strength of all AASHTO T 283 tests are above the minimum tensile strength requirement in section 11.3
- The unconditioned tensile strength of the higher dosage mixture is higher than or within 10 psi below the unconditioned tensile strength of the lower dosage mixture.
The design shall meet the tensile strength ratio requirement of M 323.
Also, add the followingto the end:
Ifvisual strippingof theasphalt film is observed from the T283 specimensandestimated to be 5%orgreaterof thespecimenface area,furtherevaluate moisturesusceptibilitybyperformingtest procedure ASTM D3625 (BoilingWater Test).(Uncoatedareas dueto fracturedaggregate shouldnot be recordedasstripped).Whenasphaltbindercoatingisless than 95%,asdeterminedbyASTM D3625, retest themixturein accordancewith Section 11. All collectedspecimensand testdata should becarefullyreviewed priortodeterminingacceptability.If thereis anydoubtconcerningthe mixtures susceptibility,the recommendedapproach is to consider themixmoisturesusceptible.
ReviseSection 4 byadding a newSubsection as follows:
4.5Review of Job-MixFormula(JMF) -Thecontractorwill besolelyresponsible todesign amixthat meets all Departmentrequirements. The contractorwill submit therequired test results, the composition of the mixtures andthecombinedaggregategradationcurves proposed foruse in theproduction of base, binder, and wearingcourses, to the DistrictMaterialsManager/MaterialsEngineer (DMM/DME) for reviewatleastthreeweeks priorto the scheduledstart ofwork. Submit mixdesigns to theDME/DMM forreview followingthe proceduresoutlined in AppendixJ. Theacceptabilityof thebituminous concrete produced fromanymixdesign is determinedasspecified in Publication 408, Section 409 in addition to the criteriaspecifiedherein.
Whenever theContractor’s gradationsandcalculations do not check, the DMM/DMEshall request the Contractor to do additionaltestingand/orrecalculateand submit thecorrectmathematical solutions.TheDMM/DME mayrequest, at his option, to observetestingof thetrial mix. Hemayalso request thatmaterials be submitted to theMaterials and TestingDivision (MTD)for evaluation of themix.TheDepartmentreserves the right to review anydesignthrough plant production,prior to usingforDepartment work, at no additional cost to the Department. See DepartmentRevisionsto AASHTOR 35, Section 12 (page 2A-9) for EvaluatingMixCharacteristics.Also,see DepartmentRevisions to AASHTOM 323 Section7 (page 2A-14) forarecommended procedure forthe statistical evaluation ofaJMFthrough plantproduction.
AASHTO R35, Section 6. PreparingAggregateTrial BlendGradations
ReviseSubsection 6.1 completely as follows:
6.1SelectPerformance Graded Binders(PG-Binders)asspecified in the projectContract, meetingthe requirements of AASHTOM320, except as revisedin theapplicablesections of DepartmentPublication No. 37 (Bulletin25). Obtainmaterialfrom currentlyapprovedproducersandsources listed in Department Publication No. 35(Bulletin15). If 16%ormoreRAP is includedin themixtureor, if 5%or more RAPand 5%RAS is includedin themixture, adjust the PG-Bindergrade if necessaryinaccordance with the requirements of AppendixH and onlyasrecommendedbytheMTD.
Iftwo ormoremixtures are specifiedin one project Contract with all things beingequal(nominal maximum aggregate sizeof mixture, ESALs,SRL)except thespecifiedgradeof PG-Binder, it is permitted to fullydesign oneof thespecified mixtures with oneofthe specified PG-Bindersand then make three specimens in accordance with T312 atthe same JMFasphalt content for the otherPG-Binder(s). If theaveragevolumetricproperties ofthe threespecimens, such as,air voids at Nini, NdesandNmax,VMA,andVFA meet the specifiedSuperpave volumetric properties, usethe sameasphalt contentforthe otherPG-Binders. However,evaluate themixtures usingthe differentgrades ofPG-Bindersformoisturesusceptibilityinaccordance with AASHTOR 35,Section 11andas modified herein. Ifthe average volumetricproperties ofthe three specimens donot meet the specified Superpavevolumetriccriteria, proceed to thefollowingparagraph.
Iftwo ormoremixtures are specifiedin one project contract with allthings being equal(nominal maximum aggregate sizeof mixture, ESALs,SRL)except thespecifiedgradeof PG-Binderand theaverage volumetric properties do not meet the specifiedSuperpave volumetric properties asdeterminedbythe procedurein theprecedingparagraph, optimum asphaltcontent must be determined foreachgrade ofPG-Binder.Usingthe samecombined gradation oftheaggregate,follow theprocedureoutlined inAASHTO R 35 Section 10.
Revise Subsection 6.4 and 6.5 as follows:
Changereference of T 27to PTM No. 616 andreference of T 11 to PTM No. 100.
ReviseSubsection 6.6 byadding the following tothe end:
Determine the Apparent Specific Gravityof mineralfiller, if added separately(T133).At leastthree determinations should bemadeand the average value used.
ReviseSubsection 6.8 byadding the following tothe end:
See Note4 and Department Revisions to Note4concerningtrial blends. TheDME/DMM may,attheirdiscretion, eliminatetheneed forthreetrial blends based on aProducer’s previousSuperpavemixdesign workwith specificaggregate blends. Whenpreparingtrial blends,varythe primarycontrol sieve(PCS) on eachtrial blend by4 to5%.
Note 5A-M 323, Table3 is incorrect and the Departmentrevised the table bychanging“Max. 90"for the firstsieve size smallerthan the nominalmaximumaggregate size for eachgradation to “Max. 89". This change is more consistent withthe definitionasstated in Subsection 3.10. (SeeDepartmentRevisions to AASHTOM323, Section 6.1.2 Table3).Also seeNote4.
ReviseSubsection 6.9 byadding the following tothe end:
Source propertyof Toughness (Abrasion) has been added to aggregaterequirements(SeeDepartmentRevisionsto AASHTOM 323, Section 6 - CombinedAggregateRequirements).
Revise Note6 byaddingthe following totheend:
It is recommended toperform the fineaggregate qualitytests on thecombinedaggregate trial blend andnot estimatethe fineaggregate qualitytests mathematicallyfrom qualitytests on each fineaggregate stockpile.
AASHTO R35, Section 7. Determining an InitialTrialBinder Content for EachTrialAggregate Gradation
ReplaceNote7 withthe following:
When usingRAP, RASora combination ofRAP and RAS, the Department’smodifieddesignprocedures (seeAppendixH)shall be followedexclusively.
AASHTO R35, Section 8. CompactingSpecimensofEachTrialGradation
Revise the Section 8, Table 1 Row for DesignESALs ≥30 Million and Columns forCompactionParametersas follows:
Table 1 – SuperpaveGyratoryCompaction Effort
DesignESALsa(Millions)CompactionParameters
NinitialNdesignNmax
≥308100160
ReplaceSubsection 8.2with the following:
Condition the mixturesaccordingto Bulletin 27,AppendixI,andcompactthespecimens to Ndesigngyrations in accordance withT 312. Record the specimen height tothe nearest 0.1 mm aftereach revolution.
Replacereference to AASHTO T166 with PTMNo. 715, typical throughout.Replacereference to AASHTO T275 with PTMNo. 716, typical throughout.
ReviseSubsection 8.3 byadding the following to the end:
Note 10A – When the estimated design traffic level is between 0.3 and <3 million ESALs, the District may, at its discretion, specify Ninitial at 6, NDesign at 50, and Nmax at 75.
In theevent a discrepancyoccursbetween lab test data, PTM No. 715, Method A willbethe referee method. Notes 9 and 10 in reference to Table 1 apply.
AASHTO R35, Section 10. Selecting theDesign Binder Content
ReviseSubsection 10.1 byadding the following:
When a design usinglessthan 16%RAPora design using5% RAS with no RAPisdeveloped based on apreviouslyapprovedvirginaggregate design of similarcomposition(gradation,aggregate source, binder content), onlyspecimenswithestimateddesign binder content maybe necessary,asdirected in theDepartment’smodifieddesignprocedure.(seeSee AppendixH)
ReplaceSubsection 10.2with the following:
Condition the mixturesaccordingto Bulletin 27,AppendixI,andcompactthespecimens to Ndesigngyrations in accordance withT 312. Record the specimen height tothe nearest 0.1 mm aftereach revolution.
ReplaceSubsection 10.7.1 with the following:
Condition the mixturesaccordingto Bulletin 27,AppendixI,andcompactthespecimens accordingtoT 312 to themaximum numberofgyrations,Nmax,fromTable1.
ReviseSection 10 byaddingthe followingSubsections:
10.7.3Preparereplicate(Note 8)specimens composedof thedesignaggregatestructureat the design binder content to confirm that%Gmm designsatisfiesthe designrequirements in M 323.
10.7.4Condition the mixtures accordingto AppendixI, and compact the specimensaccordingto T 312 to thedesign number of gyrations,Ndesign,fromTable 1.
10.7.5Determine theaverage specimen relative densityatNdesign,%Gmm design,byusingEquation 15A, and confirm that%Gmm designsatisfies the volumetricrequirement in M323.
%Gmm design=100
GmbGmm
(15A)
Where:
%Gmmdesign= relative densityatNdesigngyrationsat the design binder content.
10.7.6Place each replicate specimengyrated to Ndesignon a separatepanand place eachpan in an oven set atthemidpoint of the minimum and maximum mixturetemperaturerange for thePG BinderGrade. Heateach specimen until it is sufficientlysoft toseparate with a spatula ortrowel. Warm theasphalt mixtureuntil it can behandled ormixed. Determine the asphaltcontentandgradation of eachspecimenaccordingtoPTM No. 757 orPTM No. 702 and PTM No. 739.Comparethegradation of eachspecimen to the originalgradation ofthe preparedspecimensand the JMF. If thegradation ofthe specimensis not within the singleand multiple sample tolerances ofPub. 408, Section 409, TableA,whencompared to theJMF,either thespecimenswerenot prepared with enough precision to properlyrepresent theJMFor, significantbreakdown of theaggregate hasoccurredduringlaboratorycompactionifa finergradation is determined.
Ifit is determined that the sample preparation wasnot precise,repeat Section 10startingat Section 10.7.3until precision is obtained with eachspecimen meeting themultiple sample tolerances in Pub. 408, Section 409, TableA. Ifit is determined thatthe sample preparation was not precise,review laboratoryprocedures to ensurespecimenpreparation ispreciseandrepeatanyworkwhere precisionwasnotmaintained.
Ifit is determined that the laboratorycompactionresultedin breakdown of theaggregate and thegradationaftercompaction no longer meets the single andmultiplesample tolerances of Pub. 408, Section 409, Table A, the mixtureshould be consideredsuspect. Eitherthe aggregate structureof themixture results in a“harsh”mixture thatis not conducive to compaction orthe aggregatequalityis poor. Harsh mixtures shouldbe redesigned to make them more workable.Poorqualityaggregates should beinvestigated in cooperation with the Districtand not used until the investigation iscompleted.
AASHTO R 35, Section 11. Evaluating Moisture Susceptibility
ReviseSection11byaddingNotesasfollows:
Note17A-Ithasbeenshown thatthechemicalcompositionofasphaltbinders,aggregatesandanymixtureadditivescanhaveastronginfluenceontheresultsobtainedfromthesetestingprocedures.Therefore,itisrecommendedthatthe sourcesofmaterials(binderandadditives)usedinthedesignprocessbethesameasthematerialsthatwillbeincorporatedinthemixtureduringproduction.Ifeitherofthesecomponents changeatthetimeofproduction,theactual
productionmixturemustbeverifiedbyretesting,initiallywithASTMD3625(BoilingWaterTest)asascreeningtest. Otherwise,thedesigntestingmaynotberepresentative.
Note17B–IfmultiplemixdesignsusethesameaggregatecombinationandthesamePGbinderbutdifferinoptimalasphaltcontent,theDMMIDME DMM/DME mayelecttorequiremoisturesusceptibilityevaluationofonlythemixwiththelowestasphaltcontent.The"sameaggregatecombination"canbedefinedasmixdesignswithgradationtargetsdifferingbylessthanthemultiplesampletolerancesofPublication408,Section409,TableA.
Note17C-Allmoisturesusceptibilitysamplingand testingshallbe directlywitnessedanddocumentedbyPennDOTinspectionpersonnelunlessotherwiseapproved,inwriting,bytheDME/DMM.
ReviseSubsections11.1and11.2bycompletelydeletingexistinglanguageandreplacingwithlanguageasfollows:
11.1Prepareeitherlaboratory-mixed,laboratory-compactedspecimensorfieldmixed(plant-mixed),laboratory-compactedspecimensaccordingtoAASHTOT283withmodificationsasfollows:
AASHTOT283,Section6.5,addthefollowingtotheend:
Preparebatchescomposedofthedesignaggregatestructureatthedesignbindercontent.
AASHTOT283,Section6.5,revise thecompactionmethodasfollows:Compactthe specimensaccordingtoT312.
AASHTOT283,Section7.3,revisecompletelyasfollows:
Field-mixed(plant-mixed)samplesareonlypermittedtobeobtainedfromasphaltproductionplantsandevaluatedformoisturesusceptibilitypriortoshipmenttoanyPennDOTfundedprojectlocation.ObtainalargeenoughsampleaccordingtoPTMNo. 746tosplitthesampleandpreparetherequiredsixcompactedspecimens,totestthesampleaccordingtoPTMNo.757orPTMNo. 702andPTMNo. 739,andtoperformtwotestsaccordingtoAASHTOT209asrequiredinAASHTO
T283,Section9.1. Comparethegradationandasphaltcontentofthetestedmaterialtothemultiplesample(n2:3)tolerancesinPublication408,Section409,TableA. Ifanyoftheindividualsievesizegradationsorasphaltcontentareoutsideofthemultiplesample(n2:3)tolerancesinPublication408,Section409,TableA,thecompletesampleisinvalidandmustbediscarded.
AASHTOT283,Section7.4,revisethefirstthreesentencescompletelyasfollows:
Noloose-mixcuringasdescribedinSection6.4shallbeperformedon
thefield-mixedsamples.Aftersampling,dividethesampletoobtainthedesiredsizeinaccordancewithR47.Next,placethemixtureinanovenfor2h±10minatthecompactiontemperature±3°C(5°F)prior tocompaction.
AASHTO T 283, Section 8, delete Section 8 in its entirety including Sections 8.1, 8.2 and 8.3.
11.2Evaluateandgroup,precondition,test,andcalculatethetensilestrengthratioaccordingtoAASHTOT283withmodificationsasfollows.ThedesignshallmeetthetensilestrengthratiorequirementofAASHTOM323.
AASHTO T 283. Section 9.1, revise completely to read as follows:
Aftercuringand/orheatingthemixturesamplestothecompactiontemperatureasdescribedinSections6.4 and6.5orSection7.4,as
appropriate,determine thetheoreticalmaximumspecificgravity(Gmm)ofthosesamplesaccordingtoAASHTOT209asmodifiedbyBulletin27,AppendixIexceptthesample conditioningrequiredforGmminBulletin27,AppendixIisnotrequired.DetermineGmmonaminimumoftwosamplesandaveragetheresultsforcalculatingpercentairvoidsofthespecimens.
AASHTO T 283, Section 9.4, revise first sentence completely as follows:
Determinethebulkspecificgravity(GrobGmb)ofeachspecimenaccordingtoPTMNo.715.
AASHTO T 283. Section 9.5, revise completely to read as follows:
Calculatethepercentageofairvoids(Pa)inaccordancewithT 269usingthebulkspecificgravity(Gmb)andthe theoreticalmaximum specificgravity(Gmm)asdeterminedinthe revisedAASHTOT283Sections9.4and9.1
AASHTO T 283. Section 10.3.l, add new Note 5 and Table as follows:
Note5-Thefollowingtableisprovidedtohelpwithunderstanding vacuumpressurereadingsandunderstandingweakerandstrongervacuum.
UnderstandingVacuumGaugePressure / ReadingsVacuumGauge Type / UnitofMeasure / VacuumReadingwithNoVacuumApplied / Vacuum ReadingwithWeakest Vacuum Applied / VacuumReadingwithStrongestVacuumApplied
Partial/Relative / InchesofMercury(Hg) / 0(Zero) / 10in.Hg / 26in.Hg
Partial/Relative / mmofMercury(Hg) / 0(Zero) / 254mmHg / 660mmHg
Absolute / Inches ofMercury(Hg) / Approximately29.9 in. Hg / 19.9in.Hg / 3.9in.Hg
Absolute / mmofMercury(Hg) / Approximately760 mm Hg / 506mmHg / 97.5mmHg
AASHTO T 283, Section 10.3.2, revi se completely to read as follows:
Determinethemassofthesaturated,surface-dryspecimenafterpartialvacuumsaturation(B')byPTMNo.715.
AASHTO T283,Section12.l,addnewSubsection12.1.1asfollows:
12.1.1 Calculatetheaverage(.X )x)andstandarddeviation(s)oftensilestrengthsforboththedrygroupofspecimensandthefreeze-thawgroup.CalculatetheCoefficientofVariation(C.V.)foreachgroupbydividingthestandarddeviationbytheaverage:
(%)
IftheC.V.isgreaterthan 12%forthedrygroup, or24%forthefreezethawgroup,thetestresultsshouldbeviewedassuspectandanewsubsetofspecimenspreparedandtested.
Ifonlyoneof theresultsissuspectandanalysisaccordingtoPTMNo.4identifiesthatresultasanoutlier,areplacementisinitiallyonlyrequiredforthatspecimen.If theC.V.consideringthereplacement specimeninplaceoftheoutlierisstillgreaterthantheacceptablelimit,prepareandtestanentiresubsetofnewspecimens. Eachgroupofspecimens,dryorfreeze-thaw,isdefinedasasubset.
ReviseSubsection11.3 byaddingthefollowing tothe end:
IftheaveragedrystrengthformixturescontainingPG64-22orPG76-22islessthan80psi (552kPa)ortheaveragedrystrengthformixturescontainingPG58-28islessthan65psi(448kPA),themixisunacceptable.Anymixturewithanaveragewet/freezestrengthlessthan50psi(345kPa)isunacceptable.Moisturesusceptibilitytestingmustbereevaluated,ataminimum,onceevery5 five years,ifmixturecomponents,sources,andJMFtargetsremainthesame,toaccountfor variationsinaggregatesourcesandothermixcomponents.Whencomponentmaterialsourceschangeorcomponentmaterialproportions orJMFtargetssignificantlychange,asdeterminedbytheDME/DMM,moisturesusceptibilitymustbereevaluated.
IfanyJMFfailstomeetanyoftherequirementsaboveorinAASHTOT283,anyretestor testingofJMFversionsofthesameaggregatecombination(outlinedinnote17Babove)mustbeapprovedbytheDME/DMM.
Compute the dosage rate of liquid anti-stripping agent as follows:
- For mixtures that contain no RAP or RAS, or conform to Tier 1 of appendix H, compute the anti-strip dosage rate based on the virgin asphalt added to the mixture.
- For mixtures that contain RAP and / or RAS, and fall into Tier 2 or Tier 3 of Appendix H, compute the anti-strip dosage rate based on the total asphalt in the mixture.
Allwarmmixasphalt(WMA)versionsofJMFsmusthaveseparateevaluationsformoisturesusceptibilitytestingfromthehotmixasphalt(HMA)parentJMF. All WMA JMFs produced using a WMA Technology categorized as a mechanical foaming technology will continue to require a minimum 0.25% anti-strip additive by weight of total bituminous material in the mixture unless shown by the specified moisture susceptibility evaluation using field-mixed (plant-mixed), laboratory compacted specimens that the anti-strip additive is not required to meet the minimum moisture susceptibility requirements. InallcasesofaWMAmixtureproducedbyaWMATechnologycategorizedasafoamingadditiveorprocess (e.g.,foamingadditiveormechanicalfoaming),if theHMAversionoftheJMFrequiresananti-stripadditivetomeetthemoisturesusceptibilityrequirements,the
WMAversionofthatJMFisrequiredtocontainthesameminimumamountofanti stripadditiverequiredintheHMAversion oftheJMF.
If the Producer elects to use an alternate anti-strip additive that is not a typical amine-based anti-strip additive, contact the DME/DMM at least three weeks prior to start of work. If directed by the DME/DMM, perform moisture sensitivity analysis with the alternate anti-strip additive incorporated at the alternate anti-strip manufacturer’s recommended dosage rate. Demonstrate, by the moisture sensitivity test results that the alternate anti-strip additive meets the specified moisture sensitivity requirements. If directed by the DME/DMM, provide written documentation (e.g., research or project evaluation reports) from the manufacturer of the alternate anti-strip additive showing successful use of the alternate anti-strip additive in asphalt mixtures at the same dosage rate as is being recommended for the JMF.
IftheDME/DMMdeterminesthatmoisturesusceptibilityresultsaresuspectorinconsistentwithhistoricaldataorfieldperformance,aspecifiedlevelofanti-stripadditivemayberequiredinamixtureatnoadditionalcosttotheDepartmentpriortoapproval.