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In This Issue

NCAT Evaluates WarmMix Asphalt — Page 1

Asphalt Forum — Page 6

Asphalt ForumResponses — Page 7

Specification Corner

— Page 9

Superpave SystemDevelopment Update

— Page 10

Putting Researchinto Practice — Page 13

Monte SymonsJoins Auburn University

— Page 14

A Publication of the National Center for Asphalt Technology, Auburn University Volume 17, Number 2 FALL 2005

AUBURN UNIVERSITY

NCAT EVALUATES WARM MIX ASPHALT

In addition to lower emissions warm mix asphalt hasseveral advantages over hot mix asphalt such as fuel energysavings, decreased binder aging and an extended pavingseason (Photo courtesy: Matthew Corrigan, FHWA)

The National Center for AsphaltTechnology (NCAT) is evaluatingwarm mix asphalt (WMA)technologies. WMA technologyallows the mixing, lay down, andcompaction of asphalt mixes atsignificantly lower temperaturescompared to hot mix asphalt (HMA).The technology can reduce productiontemperatures by as much as 30percent. Asphalt mixes are generallyproduced at 300°F (149°C) or greatertemperatures in the U.S. dependingmainly on the type of binder used.WMA mixes can be produced attemperatures of about 250°F (121°C)or lower.

WMA offers the followingsignificant advantages:

• Reduced Fuel Consumption.The most obviousbenefit of WMA is thereduction in fuelconsumption. Fuel isused to dry and heat theaggregate. Studieshave shown that lowerplant mix temperaturesassociated with WMAcan lead to as much as30 percent reduction inenergy consumptioncosts.

• D e c r e a s e demissions . WMAproduces emissions(both visible and nonvisible) from theburning of fossil fuels

at a significantly reduced levelcompared to HMA. This would permitasphalt plants to be located in andaround areas such as large metropolitanareas that have air quality restrictions.The decrease in emissions may representsignificant cost savings.

• Decreased fumes and odor. WMAproduces lower fumes and odor both atthe plant and the paving site comparedto HMA. This would also result inimproved working conditions at bothplaces.

• Decreased binder aging. Short-term aging of liquid asphalt binder takesplace when it is mixed with hotaggregate in the pug mill or mixingdrum. This aging is caused by the lossof lighter oils from the liquid asphalt

(continued on page 2)

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National Center for Asphalt Technology, 277Technology Parkway, Auburn, Alabama 36830Phone: (334) 844-NCAT (6228) Fax: (334) 844-6248

ASPHALT TECHNOLOGY NEWS (Library of CongressCatalog No. ISSN 1083-687X) is published by the NationalCenter for Asphalt Technology (NCAT) of AuburnUniversity. Its purpose is to facilitate the exchange anddissemination of information about hot mix asphalttechnology, trends, developments and concerns. Opinionsexpressed in this publication by contributors and editors,the mention of brand names, the inclusion of researchresults, and the interpretation of those results do not implyendorsement or reflect the official positions or policies ofNCAT or Auburn University.

E. Ray Brown, DirectorPrithvi (Ken) Kandhal, Associate Director Emeritus/ EditorCheryl Cobb, Associate Editor, College of Engineering

NCAT Evaluates Warm Mix Asphalt(continued from page 1)

(continued on page 3)

Existing facilities can easily be converted to accomodate WMA. Atthis Florida plant, a specially built feeder (right) was used to blowAspha-min into the drum using an existing fiber addition line.

binders during mixing at high temperatures. It isbelieved that the short-term aging of the binder will bereduced significantly because the loss of lighter oils willbe less at relatively lower mixing temperatures, possiblyenhancing pavement durability.

• Extended paving season. By producing WMA atnormal HMA temperatures, it may be possible to extendthe paving season into the colder months of the year insome regions of the U.S. since the WMA additives orprocesses act as a compaction aid. In addition, bynarrowing the difference between compact iontemperature and ambient air temperature the rate ofcooling is decreased. WMA may also be transported overlonger distances as compared to HMA with reduced lossof mix temperature in the hauling units.

• Compaction aid for stiffer mixes. WMA additivesand processes may be used to improve the compactibilityof stiff mixes when mix is produced closer to typicalHMA production temperatures. Smaller reductions intemperature may also be possible. There is extensiveexperience with the use of certain types of WMA withSMA in Europe.

Similar to many of the recent advances in asphaltpaving, such as stone matrix asphalt and porous

European mix, WMA technology comes to the UnitedStates from Europe. Laboratory experiments to produceWMA began in Europe in 1995. WMA has receivedpublic attention in Europe and Australia since 2000.HMA indus t ry representa t ives observed thedemonstration of WMA technology during a EuropeanScan tour organized by the National Asphalt PavementAssociation in 2002.

NCAT was given the task of evaluating someproprietary WMA technologies from Europe and oneWMA technology recently developed in the U.S. Theobjective was to perform a laboratory study to determinethe applicability of WMA technologies/products totypical paving operations and environmental conditionscommonly found in the United States. The studies weredesigned to answer the following questions:

(a ) Does WMA technology affec t thecompactibility of asphalt mix in the Superpave gyratorycompactor and, therefore, its optimum asphalt content?

(b) Does WMA technology affect the structuralstrength of the asphalt mix in terms of resilient modulus?

(c) Does WMA technology increase the ruttingpotential of asphalt mix at high temperatures?

(d) Does WMA technology necessitate some curetime for the asphalt mix before opening to traffic?

(e) Does WMA technology increase the potential formoisture damage since the mix is produced atsignificantly lower temperatures, resulting inincomplete drying of the aggregate and moisture damagefrom water trapped in the coated aggregate?

The three most widely used technologies in Europefor producing WMA are all proprietary processes that

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(continued on page 4)Sasobit flakes for melting into asphalt binder

Sasobit prills for adding directly into pug mill or mixing drum

differ significantly in their approach. These technologiesare: (a) Aspha-min®, (b) Sasobit®, and (c) WAM-Foam®. Only the first two processes have beenevaluated by NCAT with the participation of theirsuppliers. A fourth technology, Evotherm, developed inthe U.S. has also been evaluated by NCAT.

The description of the preceding four WMAtechnologies follows together with NCAT’s findingsfrom their evaluations, if available.

Aspha-min®Aspha-min is a product of Eurovia Services GmbH

based in Germany. Aspha-min is a manufacturedsynthetic sodium aluminum silicate, better known aszeolite. The crystalline structure of zeolite has largeinterconnected spaces, which can hold water molecules.Eurovia’s Aspha-min contains approximately 21 percentwater by mass, which is released in the temperaturerange of 185-365°F (85-185°C). When Aspha-min isadded to the mix at the same time as the liquid asphalt,water is released. This water release causes the asphaltbinder to microscopically foam, which allows increasedworkability and aggregate coating at lowertemperatures. According to Eurovia’s recommendations,Aspha-min is added at a rate of 0.3 percent by mass ofthe asphalt mix, which can result in a potential 50°F(28°C) reduction in typical HMA productiontemperatures.

Aspha-min zeolite is approximately a 50-meshmaterial, which may be added directly to the pug millof a batch plant. It can be added to a drum plant throughRAP collar or pneumatically fed using a specially builtfeeder. Aspha-min is available as a fine white powderin 25- or 50-kilogram bags or in bulk for silos.

Field demonstration projects using Aspha-min to

produce WMA have been constructed in Florida,Tennessee, and North Carolina in 2004. NCATmonitored the first demonstration project constructedat Hubbard Construction’s equipment yard in Orlando,Florida in February 2004 and also collected WMAsamples for testing. Aspha-min was introduced into thedrum at the same point as the liquid asphalt. A vanefeeder controlled the addition rate. The material waspneumatically blown into the drum.

The second Aspha-min field demonstration wasconducted in Nashville, Tennessee in March 2004 aspart of the World of Asphalt meeting. The third projectwas constructed in Charlotte, North Carolina inSeptember 2004.

NCAT has completed the laboratory evaluation ofAspha-min. The final report, 05-04, can be accessed atNCAT’s website, www.ncat.us.

The following conclusions were drawn from thisstudy:

• The addition of Aspha-min zeolite lowers themeasured air voids in the Superpave gyratory compactor(SGC). While this may indicate a reduction in theoptimum asphalt content, additional research isrequired. In the meantime the optimum asphalt contentof the mixture determined without the zeolite shouldbe used. It should be noted that the optimum asphaltcontent of the mixture without the addition of the zeolitewas used for all of the testing (with and without zeolite)completed in this study.

• Aspha-min zeolite improved the compactability ofthe mixtures in both the SGC and vibratory compactor.Statistics indicated an average reduction in air voids of0.65 percent using the vibratory compactor. Improved

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(continued on page 5)Feeder for Sasobit prills (Photo courtesy: Matthew

Corrigan, FHWA)

Placement of warm mix asphalt made with Aspha-min at the2004 World of Asphalt Conference in Nashville, Tennessee(Photo courtesy: Matthew Corrigan, FHWA)

compaction was noted at temperatures as low as 190°F(88°C).

• Addition of zeolite does not affect the resilientmodulus or density of an asphalt mix. Therefore, therewould be no effect on pavement thickness design whenusing WMA produced with Aspha-min zeolite.

• Addition of zeolite does not increase the ruttingpotential of an asphalt mix. The rutting potentialincreased with decreasing mixing and compactiontemperatures, which may be related to the decreasedaging of the binder.

• There was no evidence of differing strength gainwith time for the mixes containing zeolite as comparedto the control mixes indicating that the addition ofAspha-min may not require a cure time for the asphaltmixture prior to opening to traffic.

• The lower compaction temperature used whenproducing WMA with Aspha-min may increase thepotential for moisture damage. As mentioned earlier,lower mixing temperatures may result in incompletedrying of the aggregate and the resulting water trappedin the coated aggregate may cause moisture damage.Reduced tensile strength and visual stripping wereobserved in both the control and Aspha-min zeolitemixes produced at 250°F (121°C).

• Various anti-stripping agents were evaluated tomitigate the potential for moisture damage. Hydratedlime appeared to be effective with the granite aggregate.The addition of 1.5 percent hydrated lime resulted inacceptable performance in terms of both cohesion andmoisture resistance over the warm mixtures withouthydrated lime.

• Hamburg wheel tracking results confirmed the testresults produced by the TSR testing, as well assuggesting the lime will also assist in the rutting

resistance of warm mixtures compacted at lowertemperatures due to the lime stiffening the asphaltbinder.

• More research is needed to further evaluate fieldperformance, the selection of the optimum asphaltcontent, and the selection of binder grades for lowerproduction temperatures.

Sasobit®Sasobit is a product of Sasol International, Hamburg,

Germany. Unlike Aspha-min, which relies on foam toenhance mix workability at lower temperatures, Sasobitis a paraffin-wax compound derived from coalgasification using the Fischer-Tropsch (FT) process. Thesmaller crystalline structure of the FT wax is believedto reduce brittleness at low temperatures as comparedto bitumen paraffin waxes. Sasobit is designed as an“asphalt flow improver,” both during the asphalt mixingprocess and during lay down operations, due to its abilityto lower the viscosity of the liquid asphalt. This decreasein viscosity allows working temperatures to bedecreased by 30 to 97 F degrees (17 to 54 C degrees).

Sasol recommends that Sasobit be added at a rate of0.8 percent or more by mass of the binder, but not toexceed 3 percent. Sasobit can be blended into hot liquidasphalt at the blending plant (terminal) without the needfor high shear mixing. Sasobit is available in two forms:flakes for molten additions or prills (small pellets) fordirect addition to the mix. In the United States, Sasobithas been blended with the liquid asphalt at the terminalor blown directly into the mixing chamber at the samepoint cellulose fibers were being added to an SMA.Commercial supplies of Sasobit are available in 25 kg

5

Placement and compaction of warm mix asphalt made withEvotherm near Indianapolis

bags and 600 kg super-sacks. The Maryland StateHighway Administration (SHA) used Sasobit in June2005 to produce mix for repairing deep patches. TheSasobit was added not to produce warm mix, but to actas a compaction aid in case of a stiff 19-mm mixcontaining RAP. The mix with Sasobit was workableand readily compactible. In July 2005 Maryland SHAproduced a SMA binder layer with Sasobit and reducedproduction temperature by approximately 50°F (28°C).

NCAT has completed the laboratory evaluation ofSasobit. The final report, 05-06, can be accessed at theNCAT web site.

The following conclusions which are generallysimilar to Aspha-min, were drawn from this study:

• The modified binder including Sasobit needs to beengineered to meet the desired performance grade. Asan example in this study a PG 58-28 was used as thebase asphalt with the addition of 2.5 percent Sasobit toproduce a PG 64-22 binder.

• Sasobit improved the compactibility of the mixturesin both the SGC and vibratory compactor. Statisticsindicated that an average reduction in air voids up to0.9 percent was obtained.

• Addition of Sasobit does not affect the resilientmodulus of an asphalt mix compared to mixtures havingthe same PG binder.

• Addition of Sasobit generally decreased the ruttingpotential of the asphalt mixes evaluated.

• Lower compaction temperature used in producingWMA may increase the potential for moisture damage.TSR tests indicated moisture damage in both the controland Sasobit mixes produced at 250°F (121°C). However,the addition of a liquid anti stripping agent improvedthe TSR values to acceptable levels.

• More research is needed to evaluate fieldperformance, the selection of optimum asphalt content,and the selection of binder grades for lower productiontemperatures.

WAM-Foam® (Warm Asphalt Mix Foam)WAM-Foam is a two component binder system: a

soft binder and a hard foamed binder, which areintroduced at different times in the mixing cycle duringthe production of asphalt mix. WAM-Foam is a jointventure product of Shell International PetroleumCompany Ltd., U.K. and Kolo-Veidekke, Norway. First,a soft asphalt binder is mixed with the aggregate at 212-250°F (100-121°C) temperatures to coat the aggregatefully. Next, a hard asphalt binder in the form of foam ismixed with the pre-coated aggregate. Cold water isinjected into the hard asphalt binder to produce a largevolume of foam. This combination of soft binder and

foamed hard binder acts to lower the viscosity to provideincreased workability. The resulting asphalt mixture canbe placed and compacted in the temperature range of175-195°F (79-91°C). The hard binder combines withthe soft binder to achieve the desired PG grade in themix. NCAT has not performed any laboratory evaluationof WAM-Foam.

EvothermEvotherm is a non-proprietary technology developed

especially for WMA by MeadWestvaco AsphaltInnovations in the United States. It is based on achemistry package that includes additives to improvecoating and workability, adhesion promotors, andemulsification agents. The chemistry is delivered in anemulsion with a relatively high asphalt residue(approximately 70 percent). Evotherm is stored at about175°F (80°C). The water in the Evotherm emulsion isliberated in the form of steam when it is mixed with hotaggregate. The resulting WMA appears like HMA inappearance. No plant modifications are required forusing Evotherm. The mix can be stored in silos.

To date, ten field trials have been constructed in fourcountries using Evotherm. NCAT representativesattended and tested material from a field trial ofEvotherm conducted near Indianapolis in July 2005. TheWMA using Evotherm was produced in a hybrid batch/drum plant in drum plant mode. Discharge temperaturesfrom the mixing drum stabilized at approximately 200°F(93°C). Even at such low temperatures, the WMAmixture appeared black like HMA with none of thebrown or gray coloration generally associated withemulsions. After the WMA production, the bag housewas examined. The bags and fines appeared dry.

(continued on page 8)

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ASPHALT FORUMNCAT invites your comments and questions. Questions and responses are published in eachissue of Asphalt Technology News. Some are edited for consistency and space limitations.

Connecticut (Keith Lane, Connecticut DOT)A task force has been set up to investigate options

and recommend a course of action by the end of theyear regarding the use of “quiet pavements.”

John Hanrahan (Innophos, Inc.)Please refer to Asphalt Forum Responses in the

spring 2005 issue of the Asphalt Technology Newswherein some highway agencies had expressed concernon the use of polyphosphoric acid (PPA) modifiedasphalt binders. The PPA additive has been used in smallamounts in the US and Canada by asphalt binderproducers for many years. It has allowed them toimprove the consistency of the asphalt binder andincrease its performance grade (PG) by one to twogrades in a safe, durable, and economical manner. PPA’suse in asphalt binder in the US is documented as earlyas 1972. Many thousand tons of PPA are used annuallyto modify millions of tons of asphalt binder in NorthAmerica. Europe and Latin America have also recentlybegun to use PPA for improvement of asphalt rheology.The Association of Modified Asphalt Producers(AMAP) has issued the following statement regardingPPA:

“After a review of the available information on theuse of polyphosphoric acid in the modification of pavinggrade asphalts, it is the position of AMAP that the

correct use of polyphosphoric acid in the appropriateamount can improve the physical properties ofbituminous paving grade binders. AMAP endorsesappropriate testing on the modified asphalt binder afterthe addition of any and all additives to determine thefinal product specification is met. However, incorrectapplication of the technology, as with many additives,can result in problems associated with construction and/or performance.”

NCAT (Prithvi “Ken” Kandhal, Editor, AsphaltTechnology News)

In the past some highway agencies were allowingeither fine-graded or coarse-graded Superpave mixturesand some were allowing both. What is the currentpractice in your agency and why?

Delegation of Chinese engineers visited NCAT in June this year

DOWNLOAD NCAT RESEARCHREPORTS AT NO COST

Over 80 NCAT research reports are now available as PDF(portable document format) files, which can be easilydownloaded at no cost from our web site. You will need theAdobe Acrobat Reader, which can also be downloaded freefrom our homepage, to open these files. Visit our web site atwww.ncat.us and click on NCAT Publications. Previouseditions of Asphalt Technology News are also available fromour homepage.

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ASPHALT FORUM RESPONSES

The following responses have been received to questions raised in the Spring 2005 Asphalt Forum.

(continued on page 8)

What amount of diesel fuel (in gallons) are other statespermitting to flush out filling lines on PG binderdeliveries? (Keith Lane, Connecticut DOT)

Connecticut (Keith Lane, Connecticut DOT)In response to my own question I would like to

mention the practice in Connecticut. It has beendetermined that 5 to 10 gallons of diesel fuel are used to“clear” the lines for each PG binder delivery at the HMAplant. The average delivery is 6,000 gallons of PG binderdelivered to an average 16,000-gallon capacity groundtank at the HMA plant.

Mississippi (Richard Sheffield, Mississippi DOT)The Mississippi DOT does not allow any diesel for

flushing out the lines.

Nebraska (Laird Weishahn, Nebraska DOT)The Nebraska DOT does not specify gallons, but

specifies that care shall be taken not to contaminate thePG binder.

South Carolina (Milton Fletcher, South CarolinaDOT)

The South Carolina DOT does not have a specificationon the amount of fuel used to flush out lines.

Is any agency using the latest AASHTO T-283specification with hydrated lime to detect the use ofacid modified PG binders? Is it successful? (KeithLane, Connecticut DOT)

Mississippi (Richard Sheffield, Mississippi DOT)We do not have any experience with acid-modified

binders.

What is your opinion on FHWA Technical Advisory(TA) on PWL specification development? If you havea PWL specification, does your state conform to theTA? If you do not have a PWL specification, does theTA provide the basis and encouragement to implementsuch a specification? (Gregory Sholar, Florida DOT)

Alabama (Randy Mountcastle, Alabama DOT)The Alabama DOT does not use PWL but has adopted

something simpler. We use the average of the absolutevalues of the deviation from the target. For example: If

the target air voids are 4 percent and the contractor’stest results are: 4.5, 3.5, 3.2, and 4.2 percent, theaverage deviation is 0.5 percent. We pay bonuses andmake deductions based upon this approach. We havefound that this practice gives us enough informationfor QC/QA enforcement and it is simple enough forany high school graduate to understand and implement.

Mississippi (Richard Sheffield, Mississippi DOT)We have no intention of going to a PWL-based

specification but would continue our current practiceof using a running average of QC test results. For thequality assurance, we are planning to use independentverification samples rather than samples split with thecontractors.

Nebraska (Laird Weishahn, Nebraska DOT)The Nebraska DOT does not intend to adopt a PWL

specification at the present time. Our practice of usingthe running average of four test values works very wellfor us.

Ohio (Dave Powers, Ohio DOT)The Ohio DOT will be making some revisions to its

specifications but not based on PWL. The DOT has aninternal policy used by the construction personnel forpayment deductions for out of specification test values,where material is sent to projects and used. If materialis outside specific bands and a certain number andpercentage of failed to passed tests occurs then specificdeductions are applied. Therefore, although not exactlyPWL it does address consistency in a similar manneras PWL. At only two HMA test series per productionday, the DOT does not believe that there is enoughrepresentative test data to be analyzed for a statisticalspecification for most projects. The DOT has foundduring its 20 years’ experience with the QC/QAprogram that specifications and production responseshave to be set up around each individual test becausethat is how the contractors respond to their tests.

South Carolina (Milton Fletcher, South CarolinaDOT)

The South Carolina DOT has been using a PWLspecification for several years and is presentlycomparing its procedures to those given in the FHWA

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—Asphalt Forum Responses(continued from page 7)

Technical Advisory.What is the experience of other states with asphalt

binders modified with elastomeric terpolymers?Specifically for those states satisfied with theperformance of SBS-modified asphalt binders, whatis your opinion of replacing the SBS modifier with anelastomeric terpolymer? How does the performanceof HMA pavements containing these two types ofmodif ier compare? (Al len Myers , KentuckyTransportation Cabinet)

Ohio (Dave Powers, Ohio DOT)Ohio has just started looking into this and would also

like to hear about the experience of other agencies.

Editor: Mississippi, Nebraska and South Carolinaresponded to the above question by stating they do nothave any experience with terpolymers.

The following conclusions, which are generallysimilar to those for Aspha-min and Sasobit, were drawnfrom the laboratory evaluation of Evotherm by NCAT:

• Evotherm improved the compactibility of themixtures in the vibratory compactor. Statistics indicatedan average reduction in air voids up to 1.5 percent.

• Addition of Evotherm does not affect the resilientmodulus of an asphalt mix compared to mixtures havingthe same PG binder.

• Addition of Evotherm generally decreased therutting potential of the asphalt mixes evaluated.

• Lower compaction temperature used in producingWMA may increase the potential for moisture damage.

• More research is needed to evaluate fieldperformance, the selection of optimum asphalt content,and the selection of binder grades for lower productiontemperatures.

Additional researchNCAT will continue to evaluate the WMA technology

wi th the par tnersh ip of the Federa l HighwayAdminis t ra t ion , Nat iona l Asphal t PavementAssociation, state asphalt pavement associations, andsuppliers of WMA processes/products.

Additional research is needed in the following areas:• Mix designs: Modifications to Superpave mix

NCAT Evaluates Warm Mix Asphalt(continued from page 5)

technology, if required, for designing WMA, need tobe established. Selection of binder grades for lowerproduction temperatures needs to be examined.

• Long-term performance: Durability of asphaltpavements constructed with WMA needs to beinvestigated in terms of binder effects (binder is eitherfoamed or chemically modified) and increased potentialfor moisture damage.

• Cost benefits: Reduction in fuel consumption andemissions need to be quantified to ascertain costbenefits.

• Plant operations: The suitability of WMA for highproduction rates in the U.S. needs to be examined.

• Control of mixing process: Since WMA has adifferent mixing process than the conventional HMA,new guidelines need to be developed for proper QC/QA of the produced mix.

• Workability at the paving site: Although theWMA may appear workable and easily compactiblewhen produced, it should remain workable at the pavingsite as well. This needs to be investigated on fielddemonstration projects.

• Quick turnover to traf f ic : More f ie lddemonstration projects are needed to verify that theWMA pavements can be opened to traffic as soon aspossible after construction similar to or earlier than theconventional HMA pavements.

A SHORT COURSE IN ASPHALTTECHNOLOGY

This training course has been developed by NCAT forpracticing engineers who are involved with hot mix asphalt(HMA). The purpose of this one-week intensive course,which will be offered on January 30-February 3, 2006 andFebruary 27-March 3, 2006, is to provide a generalunderstanding of all phases of HMA technology. Uponcompletion, the participant will be able to makeknowledgeable decisions related to HMA pavements andcommunicate effectively with asphalt specialists. NCAT willaccept applications from private and public sectors practicingengineers in the United States and abroad. This includespersonnel from the FHWA, state DOTs, FAA, Corps ofEngineers, Air Force, Navy, county engineers, city engineers,consulting engineers, and contractors. Please call334.844.6228 ext. 110 or visit our web site at www.ncat.usClick on “Education” at the top of the page, then click on“Upcoming Training Courses” for a brochure or information.On-line registration is now available.

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SPECIFICATION CORNER

Connecticut – After a couple of years of quality controltesting by the contractor, which is used as the basis ofpayment, there is a renewed emphasis ensuring that astate testing representative be present during production.Additional resources are being allocated in time for the2006 construction season.

Kentucky – The Kentucky Transportation Cabinet isconstructing several experimental projects in 2005 aspart of a research effort to address permeability concernsin HMA pavements. Multiple strategies to reducepermeability are underway. One approach involves aspecification with an increased core density requirementfor surface courses, which will require at least 93.5percent of theoretical maximum density for the mainlineand, at least 92.0 percent of theoretical maximumdensity for longitudinal joints. Another strategy featuresa specification for the permeability of HMA surfacepavements as measured by an in-situ, air-inducedpermeameter developed by the Kentucky TransportationCenter. Finally, on selected pavements, it is planned toconstruct the surface course layer at a lift thickness-to-nominal maximum aggregate size ratio of 4.

Mississippi – The Mississ ippi Department ofTransportation is considering implementation of theAsphalt Pavement Analyzer (APA) as a specificationrequirement. Recent research results indicate a prettygood correlation between field performance and APAresults for high-traffic surface mixes in Mississippi.Fine aggregate angularity (FAA) requirements are oftendifficult for the contractors to meet. The reproducibilityof the FAA test is also a problem. The criteria foracceptable APA rut depths has not been established asyet, but when it is, it should be a relief for the contractorswho do not meet the FAA requirements but meet theAPA criteria.

Ohio - An incentive surface smoothness note has beendeveloped for thin lifts and mill and fill jobs in additionto the existing note for thicker lift projects. There is amovement towards an IRI specification with high-speedequipment. Eventually all projects will have smoothnessrequirements.

It is planned to use notched wedge longitudinal jointwith specific equipment requirements for constructingthe joint. Field trials are expected in 2006. Also, aspar t o f th i s change the Ohio Depar tment ofTransportation (ODOT) will be measuring and payingfor density at the joint as well as the mainline as amodification to the exist ing incentive densityspecification.

ODOT has added requirements for specific pavingequipment to be equipped with anti-segregation devicesto eliminate dual parallel longitudinal cracking due tolongitudinal segregation created by this equipment.They are based on an ODOT review and the originalstudy conducted in Colorado.

ODOT has started a new program for approvingpaving foremen and superintendents. It requires specifictraining conducted by industry. The focus for retainingapproval is a “meaningful immediate response todeficiencies as outlined in the specifications.”

South Carolina – South Carolina Department ofTransportation had originally planned to use theSuperpave gyratory compactor for designing 100percent of the mixes in the state. However, due to someunforeseen circumstances, this action has been delayedto early 2006.

The Department is presently reviewing its RAPspecification to allow a higher percentage of RAP inmixtures if a contractor utilizes fractionation of the RAPon the 1/4 inch sieve.

PROFESSOR TRAINING COURSE INASPHALT TECHNOLOGY

NCAT has written and published an up-to-date collegetextbook on asphalt technology. NCAT has also developeda training program for college and university civilengineering faculty that will allow them to offer state-of-the-art undergraduate and elective courses in asphalttechnology. This 8-day intensive course is conducted atNCAT in June every year. In 2006, it will be held on June20-29. The course has been updated to include Superpavebinder and mix technology, and stone matrix asphalt (SMA).Some financial assistance to defray course expenses ispossible. Please call NCAT at 334.844.NCAT for brochureor information or visit our web site at www.ncat.us.

JOIN USWe at NCAT hope you enjoy this issue of AsphaltTechnology News. It is provided free of charge. If youwish to be added to our mailing list, please send yourbusiness card or your name, company, mailing address,and email address (ATN is sometimes distributed byemail only) to us and indicate whether you prefer toreceive ATN in the mail or by email. Send yourinformation to:

Prithvi (Ken) KandhalAssociate Director Emeritus, NCAT277 Technology ParkwayAuburn, AL 36830pkandhal@eng.auburn.edu

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SUPERPAVE SYSTEM DEVELOPMENT UPDATEThe Superpave system of asphalt paving materials

selection and mixture design was an outcome of the 5-year, 50-million dollar Strategic Highway ResearchProgram (SHRP), completed in 1993. During the last12 years incremental improvements have been made tothe Superpave system based on experience during itsimplementation and research conducted on specifictopics. Major Superpave related research projects havebeen sponsored directly or indirectly by the statehighway agencies and the industry. The major researchprojects listed below were undertaken by the NationalCooperative Highway Research Program (NCHRP) toimprove the Superpave System.

The Superpave Sys tem has been improvedincrementally in terms of specifications and test

methods based on the results from the Superpave relatedresearch projects. In the past, this newsletter has carrieda column “Superpave Update” to report the progress.The following update including some excerpts is basedon the report of the TRB Superpave Committeesubmitted to AASHTO and the Federal HighwayAdministration (FHWA) in April this year.

• High-Temperature Binder Selection ProcedureRecent FHWA-directed research has sought to refine

the procedure used to select the high-temperatureperformance grade for Superpave PG binders. “Theoriginal SHRP-developed procedure used as a selectioncriterion the average pavement temperature of the

(continued on page 11)

RESEARCH IN PROGRESSWe have discontinued the publication of this column inthis newsletter because it can now be accessed on NCAT’shomepage (www.ncat.us). Click on “Information” at thetop of the page, then “Research in Progress.” It is updatedfrequently based on the information received from theDepartments of Transportation and other sources.

NCAT has a domain name, to make it easier to findour web page. ww.ncat.us is the new address, but you canalso reach our web page by going to our old address,www.eng.auburn.edu/center/ncat/.

NCAT HAS DOMAIN NAME

9-07 Field Procedures and Equipment to Implement SHRP Asphalt Specifications9-09 Refinement of Superpave Gyratory Compaction Procedure9-09(1) Verification of Gyration Levels in N

design Table

9-10 Superpave Protocols for Modified Asphalt Binders9-12 Incorporation of Reclaimed Asphalt Pavement in the Superpave System9-13 Evaluation of Water Sensitivity Test9-14 Investigation of the Restricted Zone in the Superpave Aggregate Gradation Specification9-16 Relationship Between Superpave Gyratory Compaction Properties and Permanent Deformation

of Pavements in Service9-18 Field Shear Test for Hot Mix Asphalt9-19 Superpave Support and Performance Models Management9-25 Requirements for Voids in Mineral Aggregates for Superpave Mixtures9-29 Simple Performance Tester for Superpave Mix Design9-30 Experimental Plan for Calibration and Validation of HMA Performance Models for Mix

and Structural Design9-30A Calibration of Rutting Models for HMA Structural and Mix Design9-31 Air Void Requirements for Superpave Mix Design9-33 A Mix Design Manual for Hot Mix Asphalt9-34 Improved Conditioning Procedure for Predicting the Moisture Susceptibility of HMA Pavements9-35 Aggregate Properties and Their Relationship to the Performance of Superpave – Designed HMA:

A Critical Review9-36 Improved Procedure for Laboratory Aging of Asphalt Binders in Pavements9-38 Endurance Limit of HMA Mixtures to Prevent Fatigue Cracking9-39 Procedure for Determining Mixing and Compaction Temperatures of Asphalt Binders in HMA9-42 History of Superpave and its Implementation (anticipated)

NCHRP Projects undertaken for improving the Superpave System

11

temperature behavior (i.e. rut resistance) of modifiedasphalts.”

There appears to be a growing use and mixed reactionto acid modification of asphalt binders for improvingrut resistance. “Preliminary research confirms thataddition of small quantities of polyphosphoric acid doesindeed increase the high-temperature stiffness of asphaltbinders without, apparently, adversely affecting the low-temperature properties. There is a body of anecdotalexperience, however, that indicates acid modificationinteracts adversely with anti-stripping agents added tocontrol moisture damage and that the increased rutresistance declines over time. Some instances of earlyfailure of pavements using acid-modified asphalt haveled some state DOTs to ban its use. We raise this issuenot because we have any recommendations on the meritsor demerits of acid modification – we have seeninsufficient evidence to do so – but because it illustratesthe need to continue research to develop methods toreliably characterize the properties of modified asphalts.There will always be new modifiers. What is needed isa set of laboratory test methods to adequately assess aspecific modifier’s potential to improve pavementperformance.”

• Superpave Gyratory Compactor IssuesThe verification of the angle of gyration is essential

to ensure comparable results from different Superpavegyratory compactors (SGC). The mixture ETG hasconcluded that measurement of the internal angle maylead to better comparability between compactors thanusing the external angle measurement. Consequently,an optional provision to measure the angle of gyrationexternally as well as internally has been included inAASHTO T 312-03, “Preparing and Determining theDensity of Hot-Mix Asphalt Specimens by Means of

(continued on page 12)

hottest consecutive seven-day period. While thiscriterion provided improved resistance to pavementrutting, performance observations showed thatconsiderable variation in rutting has occurred atgeographically disparate sites with similar seven-dayhigh temperature his tor ies and s imilar t raff iccharac te r i s t ics . Us ing the f lex ib le pavementperformance models included in the NCHRP 1-37aPavement Design Guide, the FHWA research showedthat this variation could be reduced if the selectionprocedure considered cumulative hours at elevatedpavement temperatures instead of the seven-dayaverage . This c r i te r ion does a be t te r job ofdistinguishing between, for example, the binder graderequirements of pavements in Idaho and Florida. Whileboth locales might have the same average highest sevenconsecutive day temperature, over a summer season theFlorida pavements will accumulate many more hoursat elevated temperature. This difference is reflected ina greater propensity for rutting and, thus, the need for astiffer asphalt binder. This new selection criterion hasbeen added to the latest version of the binder selectionsoftware (LTPPBind Version 3.0).”

• Improved Data Screening for the Direct Tension Test“AASHTO Test Method T 314 Determining the

Fracture Properties of Asphalt Binders in DirectTension, is used in combination with the Bending BeamRheometer test to determine the critical crackingtemperature of asphalt binders. Variability of test resultshas inhibited general use of this test. Recent researchunder the direction of FHWA has developed a new datascreening method aimed at reducing this variability. TheExpert Task Group (ETG) on Asphalt Binders reportsthat it has monitored this research and has concludedthe new screening process would be a useful additionto Test Method T 314.”

• Asphalt Binder ModificationResearch is continuing at the FHWA to extend the

Superpave binder selection standards to modifiedasphalt binders more reliably. “It has always been a goalto make the Superpave system blind to modifiers andadditives. In other words, the system would be asreliable in characterizing critical properties of asphaltmodified with any additive as it is with unmodifiedasphalts. Because various additives and modifiers relyon different mechanisms to modify the physicalproperties of asphalt, this is a challenging assignment.Although incomplete, the FHWA research has identifiedsome promising test methods to characterize the high-

Superpave mix design workshop will be held at NCATon March 21-24, 2006. This workshop consists of threeand a half days of intensive lecture, demonstration, andhands-on training on Superpave volumetric mix designprocedures. Upon completion the participants will be ableto conduct the Superpave mix designs in their laboratories.

Please call 334.844.NCAT (6228) or visit our web siteat www.ncat.us (Click on “Education” at the top of thepage, then click on “Upcoming Training Courses”) for abrochure or information. On-line registration is nowavailable.

SUPERPAVE MIX DESIGN WORKSHOP

12

the Superpave Gyratory Compactor.” A provisionalstandard has also been published for the dynamic anglevalidator (DAV) operation. Devices have beendeveloped to measure internal angle without using HMAin the mold. The Asphalt Institute is evaluating theeffectiveness of such mixless devices under an existingFHWA contract.

• Simple Performance Tests for HMABoth NCHRP Project 9-19 "Superpave Support and

Performance Models Management" and 9-29 "SimplePerformance Tester for Superpave Mix Design" arenearing completion. These two projects respectivelydeveloped simple performance test methods and testequipment to be included in the Superpave system.

“These new tests will assess the potential of specificmixtures to meet performance expectations. Thecompletion of these projects has been long awaited bythe state DOTs. The first production models of the testequipment have been delivered and ruggedness testingis underway to determine whether the test protocols willyield results of suitable repeatability. Completion of thiswork is expected by the end of 2005. The ETG onMixtures and Aggregates is currently reviewing the testmethods and monitoring the ruggedness testing.”

• Dynamic Modulus of HMA Mixtures“Both the newly developed Simple Performance Test

and emerging pavement design and performanceprediction models rely on the determination of dynamic

modulus. Soon the Simple PerformanceTest and new models will be evaluated bythe state DOTs and others. So that theseevaluations can be correlated with oneanother, it is essential to develop a uniformstandard for the determination of a dynamicmodulus that minimizes the variability ofthe test results. To meet this goal, themixture ETG recommended a large numberof changes to the AASHTO provisionalstandard on determining dynamic modulusof HMA mixtures.”

• Capturing the History of SuperpaveSuperpave is a research success story.

SHRP was designed with a vision thatproperly focused, high-intensity researchcould resolve growing concerns aboutperformance of asphalt pavements. A lot ofresearch was conducted during the SHRPand the subsequent 12 years of furtherSuperpave development. However, thedocumentary background of Superpave isscattered through more than 200publications of at least six organizations.This disorganized state of Superpaverelated information is not in the interest ofthe future development of Superpavesystem and will also limit the lessons to belearned from the Superpave experience.Therefore, it is necessary to capture thehistory of Superpave starting from theinitiation of the SHRP project. Aforthcoming NCHRP project is likely toachieve this objective.

Recipients of the Asphalt Pavement Alliance’s Perpetual Pavement Award are seenhere with Jack Lettiere, 2005 AASHTO President. Back row, left to right are EricHarm, Illinois DOT; Gerald Nicely, Tennessee DOT; Larry O’Donnell and LukeStango, co-chairmen of the APA; Jack Lettiere, AASHTO; Dan Collen, County ofSanta Clara, Calif.; and Tom Peterson, Colorado Asphalt Pavement Association,who accepted on behalf of the Colorado DOT. Front row are Sam Beverage,Kentucky Transportation Cabinet; David Kopp, Texas DOT; Andrew Johnson, SouthCarolina DOT; Aaron Behrman, Ohio DOT; and Patrick Hughes, Minnesota DOT.

Asphalt Pavement Awards Presented at NCATThe Asphalt Pavement Alliance’s (APA) Perpetual Pavement Awards were

presented in a special ceremony hosted by the National Center for AsphaltTechnology in May 2005. Jack Lettiere, Jr., 2005 President of the AmericanAssociation of State Highway and Transportation Officials (AASHTO), madethe presentations. This year’s winners included the Colorado DOT, IllinoisDOT, Kentucky DOT, Minnesota DOT, Ohio DOT, Santa Clara Roads andAirport Department, South Carolina DOT, Tennessee DOT, and Texas DOT.The honored stretches of pavement ranged from interstate to rural two-laneroadways. To qualify for this prestigious award, a pavement must meet strictcriteria and demonstrate hot mix asphalt’s long-life characteristics: excellencein design, quality in construction, and value to the traveling public. It alsomust have been constructed at least 35 years ago. Engineers at NCAT evaluatedthe nominations and a panel of industry experts validated the winners.

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The following papers were presented at the annualmeeting of the Associat ion of Asphalt PavingTechnologists (AAPT) held in Long Beach, Californiain March. We are reporting observations and conclusionsfrom them, which may be of value to field engineers.These comments are obtained mostly from researchprojects with a limited scope; before application topractice we recommend that you read the entire paperto determine its limitations. Titles of the paper are given,with names of authors in parentheses, followed by abrief summary.

1. Determining Minimum Lift Thickness for HotMix Asphalt (HMA) Mixtures (Brown, Hainin andCooley, Jr)

Proper compaction of HMA mixtures is needed toensure that a stable and durable pavement is built. Fordense-graded mixes, initial in-place air voids should bebelow approximately 8 percent. One of the major factorsaffecting compaction is lift thickness. Although therehave been many studies on the effect of thickness oncompactibility of HMA mixtures, no documentedresearch has been performed to systematically determinethe minimum desired thickness of a HMA lift. TheSuperpave construction guidelines (1997) suggest thata minimum thickness (t) to nominal maximum aggregatesize (t/NMAS) ratio of at least 3.0 should be used. Butthis was based more on existing practice than ondocumented research. Some state agencies haverecommended that a minimum t/NMAS of 4.0 to beused. Thus , there i s a need to de termine therecommended minimum lift thickness for optimumcompaction.

The objective of this research was to determine theminimum recommended lift thickness t/nominal maximumaggregate size (t/NMAS) ratio for optimum compactionof HMA. A research plan was developed involvingextensive laboratory and field-testing. In order todetermine the minimum recommended lift thickness foroptimum compaction, various laboratory samples wereprepared using both a Superpave gyratory compactor(SGC) and a laboratory vibratory compactor (AVC). Also,seven field sections were built.

A total of 36 HMA mixes were designed that consistedof different aggregates types and gradations. The

aggregates utilized in this research included a crushedsiliceous gravel, granite, and limestone. The asphalt binderutilized for all mixes was a PG 64-22. All samples werecompacted using a Superpave gyratory compactor at thetemperature that provided recommended viscosity in theasphalt binder. For the Superpave mixes, each sample wascompacted to 100 gyrations. The 100-gyration level wasselected because it was a commonly used compaction effortand it has likely presented the most problems withcompaction. All designs were selected at 4.0 percent airvoids.

The experiment included four gradation shapes andthree NMASs. Three gradations fell within theSuperpave gradation control points and one gradationconformed to s tone mat r ix aspha l t (SMA)specifications. For the gradations meeting the Superpaverequirements, NMASs of 9.5, 19.0 and 37.5 mm wereinvestigated. For the SMA gradations, NMASs of 9.5,12.5, and 19.0 mm were utilized.

The property selected to define lift thickness in thisexperiment was the ratio of thickness to NMAS (t/NMAS). This ratio was selected for two reasons: (1)the ratio normalizes lift thickness for any type ofgradation and (2) a general rule-of-thumb for Superpavemixes has been to use a minimum t/NMAS ratio of 3.0.For each NMAS in the experiment, three t/NMAS ratioswere investigated. For the 9.5 and 19.0 mm NMASSuperpave mixes and all three SMA NMASs (9.5, 12.5,and 19.0 mm), t/NMAS ratios of 2.0, 3.0, and 4.0 wereused.

For the 37.5 mm NMAS Superpave mixes, ratios of2.0, 2.5, and 3.0 were investigated. The 4.0 t/NMASwas excluded for the 37.5 mm NMAS mixes since thisratio would produce a 150 mm lift thickness, which isunlikely to be used in the field. The desired thicknessesof compacted specimens were achieved by altering themass placed in the mold prior to compaction. Threereplicates of each aggregate type-gradation-NMAS-thickness combination were compacted using acompaction effort similar to that used in the mix design.

Testing of each sample after compaction includedmeasuring the bulk specific gravity of each replicateusing the vacuum sealing method. The relationships

PUTTING RESEARCH INTO PRACTICE

(continued on page 14)

14

between air voids and t/NMAS were analyzed todetermine the minimum t/NMAS for a given NMASand mix type. Since a constant compaction effort wasused, the differences in air voids should be caused bythe differences in the thicknesses of the specimens. Itwas expected that as the t/NMAS ratios increased theair voids would decrease until the minimum desired t/NMAS has been reached. It was intended to determinethe t/NMAS at which the air voids began to level outand to pick that t/NMAS level as the minimum levelrecommended for achieving best compaction results.

Based upon the results of this research, the followingconclusions were drawn and recommendations weremade:

• The density that can be obtained under normalrolling conditions is clearly related to the t/NMAS ratio.For improved compactibility, it is recommended that

the t/NMAS be at least 3 for fine-graded mixes and atleast 4 for coarse-graded mixes. The data for SMAindicates that the ratio should be at least 4. Ratios lessthan these suggested numbers could be used but it wouldgenerally require more compactive effort to obtain thedesired density. This work should not be used toestablish the maximum t/NMAS ratios. Within the rangeof t/NMAS values evaluated, a t/NMAS greater than4 did not significantly decrease the density obtainedfor the standard compactive effort. However, care mustbe exercised when the thickness gets too large to ensurethat adequate density is obtained.

• The results of the evaluation of the effect of mixtemperature on the relationship between density and t/NMAS indicate that one of the reasons for low density inthinner HMA sections (lower t/NMAS) is the more rapidcooling of the mixture. Hence, for thinner layers it is evenmore important that rollers stay very close to the paver sothat rolling can be accomplished prior to excessive cooling.For the conditions of this study, the mixes placed at theNCAT test track at 25 mm thickness cooled twice as fastas mixes placed at 37.5 mm thickness. For thicker sections(larger t/NMAS) the rate of cooling generally does notcreate a significant compaction problem.

• Evaluation of the effect of t/NMAS on applied energyto achieve a selected density level based on gyratorycompacted samples suggests that as t/NMAS ratiodecreases, more applied energy is required to compactmixes to a specified density. This required energy beginsto increase rapidly for decreasing t/NMAS when the t/NMAS drops below 4. This does indicate that the energycalculated in the Superpave gyratory compactor can beused to help understand the effect of t/NMAS oncompaction.

2. Evaluating Wisconsin Warranty Projects: Before,During and After the Warranty (Dukatz and Schwandt)

HMA pavements in Wisconsin were exhibitingpremature cracking, raveling and rutting in the late1980s. In 1987, the Transportation Research Boardformed a Task Force on Innovative ContractingPractices. This Task Force recommended several newcontract methods with the potential to reducedepartment costs and improve quality. The WisconsinDepartment of Transportation (WisDOT) chose toinvestigate warranties as a method of obtaining qualityHMA pavements.

(continued on page 15)

Monte Symons, P.E. has been appointed Directorof the Airfield Asphalt Pavement Technology Program(AAPTP) at Auburn University. This $1.6 million peryear grant program f rom the Federa l Avia t ionAdministration (FAA) administers research contractson asphalt airfield pavement issues. Six to eightprojects are awarded each year on a competitive basis.

After serving in the USArmy in the late 1960s,Monte Symons graduatedf rom the Univers i ty o fIllinois with a Bachelor'sand Mas te r ' s degree inCivil Engineering in 1974and 1975, respectively. InJuly 1975, Monte startedhis 30-year career workingfor the Federal HighwayAdministration. Monte hasserved in various FHWApavement and mater ia lsrelated positions and locations throughout the UnitedStates. In 1992, Monte was assigned as a loan staff toSHRP and then helped FHWA administer the LongTerm Pavement Performance (LTPP) program for nineyears. In the LTPP program, he was instrumental inthe development and implementation of the LTPPBindprogram. Monte’s last FHWA assignment beforecoming to Auburn University was with the ResourceCenter in Atlanta where he directed the NationalPavement and Materials Technical Service Team.

Monte Symons Joins Auburn University

Monte Symons

15

BOMAG Americas provided instruction and demonstration of their milling andpaving equipment for NCAT engineers and their employees. Demonstrations wereheld at NCAT Test Track. This photograph shows attendees being instructed on apaving simulator set up in the NCAT Laboratory.

The first issue in developing a Wisconsin warrantyspecification was to define the desirable quality of theWisconsin HMA pavements. It was necessary todevelop thresholds for different pavement distress typesthat WisDOT, the contractors, and the bondingcompanies felt comfortable in terms of risk. WisDOTwanted the thresholds set so that the risk of prematurepavement failure was minimized and pavement qualityenhanced. The contractors wanted thresholds that wereachievable and provided a reasonable chance of success.

Therefore, the development of warranty thresholdshinged on the comfort levels of the Department and theHMA industry. This comfort level was achieved byanalyz ing the ex tens ive WisDOT PavementManagement System data. The key indicator inWisDOT’s PMS is the Pavement Distress Index (PDI).To determine the PDI, the HMA pavement is evaluatedbased on 12 identifiable surface distresses (alligatorcracking, block cracking, transverse cracking,longitudinal cracking, flushing, edge raveling, surfaceraveling, patching, rutting, transverse distortion,longitudinal distortion and segregation). Thesedistresses were divided into tolerable and non-tolerable.A tolerable distress was defined as one where a smallamount does not pose a safety or performance concern.Further, it was realized that zero-tolerance wouldincrease costs without significantly improving theperformance. A non-tolerable distress would be one

that posed a safety or performanceconcern. The pavement distress typesto be included in warrantyspecification were listed and thresholdlevel for each distress type wasidentified. The distress threshold levelsfor tolerable distress types such aslongitudinal cracking, transversecracking and rutting were the mostchallenging to develop. For thesedistresses, the problem wasdetermining an acceptable level afterfive years of traffic. It was agreed totarget the threshold levels so that 90percent of the Pavement ManagementSystem data at five years of age wouldsucceed in meeting the threshold.

This paper was prepared to answerthree questions, which arose after theexpiry of warranty of the firstgeneration of warranty projects in

Wisconsin. First, what happens a day after the warrantyexpires was answered by the performance data givenin the paper that shows that pavements built under aperformance warranty have better performancehistories. The initial data shows that pavement life isincreased by a minimum of five years.

The second question was how better performingpavements are achieved with warranty specifications.The key is empowerment or ownership of the projectby the contractor crew and a working atmosphere ofteamwork between the state and the contractor toproduce a good product – a long lasting pavement.Quality control testing on a warranty project by thecontractor is typically conducted at a rate equal or higherthan a conventional project to reduce the contractor’srisk.

The third question was how could the overall costsof performance warranty projects be less thanconventional projects. It is easily answered – time andmaterials. Often, the HMA per ton cost is more forwarranty mix. However, the state is spending lessmoney for supervis ion, tes t ing and pavementmaintenance. The contractor has to spend less timeworking on (perceived) specification issues and canspend more effort on obtaining the best possible resultsfrom available materials. The net result is performancewarranty projects are cost effective.

16

Non-Profit OrgUS Postage

PAIDPermit # 9

Auburn University AL 36849

277 Technology ParkwayAuburn, AL 36830

NCAT's Professor Training Course in Asphalt TechnologyJune 14-23, 2005

Back row, L-R: Muhieddine Maaz, Dr. Ray Brown (Instructor), Adam Zofka, Jie Han, Michael Leaverton, Joe Wilson, Yongrak Kim, LaithTashman. Middle row, L-R: Xiang Shu, Xingjun Li, Don Watson (Instructor), B.L. Swami, Brian Fuder, Brantley Bain, Daren Zywicki, JimLynch. Front row, L-R: Osamu Takahashi, Claude Villiers, Feng-Bao Lin, Gabriel Garcia, Imad Basheer, Roy Guevara, Hao Wang, KitaeNam, Stacey Reubush Diefenderfer