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The Magazineof the Asphalt InstituteWinter 1997 Vol. 11, No. 1

CSAH

30

BLUE EARTH

8COUNTY

CSAH75Minnesota Counties

Turn to Superpave

Asphalt

2 ASPHALT Winter 1997

FeaturesJust Four More Years

Asphaltnews

Stearns County Turns to Superpave forPerformance and Durability

Night Paving with Asphalt is the Answer toRehabilitating Runway at World’s BusiestAirport

Implementing Superpave

Practical Principles for Low VolumeRoads

SAPAENews

Superpave Center Roundup

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CSAH

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BLUE EARTH

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CSAH

Minnesota Counties are using Superpavetechnology on county roads to produceperformance and durability. Story is onpage 6.

Visit the Institute in cyberspace athttp://www.asphaltinstitute.org

Winter 1997

Just Four More YearsJust four more years until the turn of the centu-ry. Not much time left to do all those thingsyou planned on doing that would benefit yourbusiness, industry, nation, family, communityand you. I’m speaking of those changes youintended to make to launch a new directioninto the 21st century. For some, it might besimply getting ready for retirement or balancingfamily commitments with the requirements ofthe job.

For others, it might be a new image and marketing strategy for your compa-ny or starting grassroots programs to inform the public of the many needs ofour highway infrastructure. Hopefully, many of you have Superpave imple-mentation in your plans over the next four years. You can read about whatsome are doing along this line in this magazine.

Regardless of whether your plans include changes in your personal or pro-fessional life, obstacles will surely surface to block the way and test yourcommitment to your goals. It will take courage, persistence and persever-ance to reach the success you seek. It might help along the way to keep thefollowing story in mind, which is taken from “Bits & Pieces.”

A young man at the age of 22 attempted and failed at business. At 23, he ranfor legislature and was defeated. At 24, he again attempted and failed atbusiness. At 25, he was elected to the legislature. At 26, his sweetheart died.At 27, he had a nervous breakdown. He ran and was defeated for Speakerat 29. He ran and was defeated for Elector at 31. He was defeated forCongress at 34 but finally was elected at 37. He then was defeated forCongress at 39, defeated for Senate at 46, and defeated for Vice President at47. After one final defeat for Senate at 49, he was elected President of theUnited States at the age of 51. That man’s name was Abraham Lincoln.

So go out there and start making those changes. Don’t let the obstacles andnay-sayers block your path, and especially don’t let the fear of mistakes stopyou. Remember these words from Peter Drucker: “The better a man is, themore mistakes he will make, for the more new things he will try. I wouldnever promote into a top-level job a man who was not makingmistakes.....otherwise he is sure to be mediocre.”

With that thought, I want to wish everyone a great new year and the best inyour personal and professional plans.

Edward L. Miller, President

AsphaltAsphalt Institute, Research Park Drive, P.O. Box 14052, Lexington, KY 40512-4052(606) 288-4960 or fax (606) 288-4999

Asphalt Magazine is printed in the USA and published at regular inter-vals by the Asphalt Institute, an international nonprofit organizationsponsored by members of the petroleum asphalt industry to serveboth users and producers of asphalt materials, through programs ofengineering service, research, and education.

Edward L. Miller, PresidentJohn Davis, EditorArticles may be reprinted with credit lines.

MEMBERS OF THE ASPHALT INSTITUTE

AMOCO OIL COMPANY, Oak Brook, Illinois *ANDRIE INC., Muskegon, Michigan ASHLAND PETROLEUM COMPANY, Ashland, Kentucky ASHWARREN INTERNATIONAL INC., Vancouver, British Columbia,

Canada ASPHALT MATERIALS, INC., Indianapolis, Indiana *BASF CORPORATION, Charlotte, North Carolina CANADIAN ASPHALT INDUSTRIES INC., Markham, Ontario,

Canada CITGO ASPHALT REFINING COMPANY, Blue Bell, Pennsylvania *COASTAL TOWING, INC., Houston, Texas COMPANIA ESPANOLA DE PETROLEOS, S.A., Madrid, Spain CONOCO INC., Houston, Texas CONSOLIDATED OIL & TRANSPORTATION COMPANY, INC.,

Englewood, Colorado ECOPETROL - ICP, Santander, Colombia EGYPTIAN GENERAL PETROLEUM CORPORATION, THE, Cairo,

Egypt EXXON COMPANY, U.S.A., Houston, Texas FRONTIER TERMINAL & TRADING COMPANY, Tulsa, Oklahoma*HEATEC, INC., Chattanooga, Tennessee HUNT REFINING COMPANY, Tuscaloosa, Alabama IMPERIAL OIL, Toronto, Ontario, Canada JEBRO, INC., Sioux City, Iowa KOCH MATERIALS COMPANY, Wichita, Kansas KOCH MATERIALS LTD., Toronto, Ontario, Canada

A Subsidiary of Koch Oil Company Ltd.LAGOVEN, S.A., Caracas, Venezuela MARATHON OIL COMPANY, Findlay, Ohio MATHY CONSTRUCTION CO., Onalaska, Wisconsin MCASPHALT INDUSTRIES LTD., Scarborough, Ontario, Canada MIDDLEPORT TERMINAL INC., Gallipolis, Ohio MOBIL OIL CORPORATION, M & R DIVISION, Fairfax, Virginia*MORANIA OIL TANKER CORPORATION, Stamford, Connecticut NAVAJO REFINING COMPANY, Artesia, New Mexico NESTE TRIFINERY PETROLEUM SERVICES, Houston, Texas NYNAS PETROLEUM, AB, Johanneshov, SwedenPARAMOUNT PETROLEUM CORPORATION, Paramount, CaliforniaPETRO-CANADA INC., North York, Ontario, CanadaPETROLEO BRASILEIRO S.A. - PETROBRAS, Rio de Janeiro,

BrazilREFINADORA COSTARRICENSE DE PETROLEO

(RECOPE), San Jose, Costa RicaREFINERIA DE PETROLEO CONCON S.A., Concon, ChileREFINERIA SAN LORENZO S.A., San Lorenzo, ArgentinaREPSOL PRODUCTOS ASFALTICOS, S.A., Madrid, Spain*SAFETY-KLEEN, OIL RECOVERY DIVISION, Breslau, Ontario,

CanadaSAN JOAQUIN REFINING COMPANY, INC., Bakersfield, CaliforniaSARGEANT MARINE, INC., Coral Springs, FloridaSENECA PETROLEUM COMPANY, INC., Crestwood, IllinoisSHELL CANADA LIMITED, Toronto, Ontario, CanadaSHELL INTERNATIONAL PETROLEUM COMPANY LIMITED,

London, EnglandSHELL OIL PRODUCTS COMPANY, Houston, TexasSOUTHLAND OIL COMPANY, Jackson, MississippiT-M OIL COMPANY, INC., Belleville, MichiganTIPCO ASPHALT PUBLIC COMPANY LIMITED, Bangkok, ThailandTRUMBULL PRODUCTS, Toledo, Ohio

A Division of Owens-Corning*ULTRAPAVE DIVISION, TEXTILE RUBBER & CHEMICAL

COMPANY, Dalton, GeorgiaUNITED REFINING COMPANY, Warren, PennsylvaniaWITCO CORPORATION, GOLDEN BEAR PRODUCTS,

Los Angeles, CaliforniaYPF S.A., Buenos Aires, ArgentinaYUKONG LIMITED, Ulsan, Korea

* Affiliate Members

Winter 1997 Vol. 11, No. 1

Asphal4 ASPHALT Winter 1997

Industry-Wide

The 105th Congress will be workingtoward a balanced budget package thatcould reduce discretionary spending andtherefore reduce federal highway spend-ing. The effort to take transportation trustfunds off-budget lost 55 supporters in theHouse in the recent election. Education ofthe newly elected Representatives plusreaffirmation of current supporters areneeded. On the House Transportation andInfrastructure Committee, 55 out of 63 willreturn for the 105th Congress.

A special panel to study transportationtaxes will seek industry’s opinions begin-ning this January or February. The panelbegan receiving briefings from federalagencies in December. Aviation will be thepanel’s first topic, then highways. Panelchairman Mac Collins (R-CA) says only pol-icy items directly affecting transportationissues will be covered. He says the panel’swork will be guided by fairness, equityand efficiency of administration.

AASHTO is promoting the “lead states”concept to advance Superpave technology.A lead team consisting of representativesfrom Florida, Indiana, Maryland, NewYork, Texas and Utah, plus industry repsfrom those states and a representative ofthe North Central Superpave Center, willprovide a pool of technical experts to assistother states with Superpave implementa-tion.

The American public supports higherspending on highways and bridges andbelieves the fuel tax is the fairest way ofraising funds for that work, according to asurvey commissioned by National QualityInitiative Steering Committee and paid forby FHWA. Nearly two-thirds of the high-way users surveyed said they wanted

improvement in pavement conditions, traf-fic flow and safety. FHWA sponsored theproject to identify priorities for highwayimprovement.

Asphalt pavement performance hasincreased approximately 20 percent overthe last ten years, according to data assem-bled by DOT agencies. They credit theimprovement to the implementation ofQC/QA requirements in the mid-to-late1980s and the implementation of smooth-ness specifications in the late 1980s andearly 1990s.

The Asphalt Industry EnvironmentalOversight Committee has presented areport on the entire spectrum of asphaltfume research to the Threshold Limit Value(TLV) Committee of the AmericanConference of Governmental Hygienists.The TLV Committee will consider the pre-sentation and determine whether to reeval-uate asphalt fume, considering the scientif-ic uncertainties and inconclusive evidenceof any potential harmful effects. A deci-sion by the Committee is expected inMarch or April 1997.

The FHWA Binder Expert Task Grouphas recognized a 0.01 difference in m-value measurements, depending on thebrand of bending beam rheometer (BBR)used. Until differences can be resolved,the ETG recommends that agencies usingthe ATS BBR allow an m-value of 0.29 tobe acceptable. This recommendation wasbased on a testing program performed atthe Asphalt Institute’s laboratory.

The Transportation Center at theUniversity of California at Berkeley esti-mates that automobiles, on the average,use less fuel per passenger mile than masstransit. In 1980 the BTU per passengermile for autos was 4,782 and 3,008 for

mass transit. In 1993, the BTU per passen-ger mile for autos was 3,593 and 3,687 formass transit. Extra equipment on masstransit vehicles has increased fuel con-sumption at the same time ridership hasbeen falling.

Visit the Asphalt Institute on the WorldWide Web. Visit us athttp://www.asphaltinstitute.org

Around the Nation

Arkansas has placed 4.3 million tons ofhot-mix asphalt using PG binders sinceMay 1995. The state has scheduled over25 Superpave projects for bids in 1997.Many of the projects will involve rehabili-tation on interstate highways.

The Railroad Transportation ResearchCenter at Pueblo, Colorado, plans toplace a railroad track bed using asphalt asunderlayment and overlayment. Theyhave the Asphalt Institute to assist themwith specifications and construction proce-dures.

A new Northeast Superpave binder, mixtraining and research center has beenestablished at the University of Connecticutin conjunction with CONNDOT. TheConnecticut Advanced PavementLaboratory (CAPLAB) director is JackStephens, Professor Emeritus, UCONN.

Construction is in progress on the 29-mile eastern section of E-470, the DenverBeltway. Colorado DOT chose 9-inch-thick Full-Depth asphalt for the initialpavement, with a 1.5-inch “staged” overlayto be added in a few years. Mix design forthe project will follow Superpave criteria.The total project will require approximate-ly 50,000 tons of asphalt cement.

ltnewsASPHALT 5Winter 1997

Indiana DOT has approved the use ofasphalt roofing shingles in hot-mix asphalt.The InDOT specification says the shinglescannot exceed 5 percent of the total mixweight and must be waste material from ashingle manufacturer. Tear-off materialfrom roofs is not permitted. If used withRAP, the maximum amount of total recy-cled material can’t exceed 20 percent, withRAP to shingles at a 4:1 ratio.

North Carolina voters approved a $950million highway bond issue in theNovember election to provide forincreased construction of secondary roads,intrastate highways and urban loops over asix-year period.

Minnesota, Wisconsin and Iowa areworking together through the NorthCentral Asphalt User/Producer Group tostandardize PG asphalt binders across statelines. The DOTs in all three states intendto specify equal grades of binder wheregeographic conditions warrant commonmaterials. This will relieve local asphaltsuppliers of the burden of supplying awide variety of PG asphalts in areas wherecommon materials can be specified.Nebraska and Michigan also expressed aninterest in joining the three-state group tofurther standardize material specificationsin the region.

Minnesota DOT has contracted with theAsphalt Institute to provide Superpavetraining in the state this winter. TheInstitute will provide three one-day intro-ductory courses and two 4-day Superpavevolumetric mix design courses, with assis-tance from local Asphalt Institute membercompanies.

A review of the cost of concrete versusFull-Depth asphalt on seven rehabilitationcontracts on the Ohio Turnpike last sum-mer shows that the square yard cost for theconcrete project was $38.89, while theaverage square yard cost for the six Full-Depth projects was $20.46, or a 47.6 per-cent savings.

Tulsa Public Works Department officialsare discussing the alternate use of asphaltdesign for city street construction andreconstruction with the Oklahoma AsphaltPavement Association and the AsphaltInstitute. Most of the recent street work inTulsa has been concrete.

The Utah Department ofTransportation is planning a 6-mile, 4-lane, crack and seat project with a 6-inchasphalt overlay on I-15 near Ogden for1997. It is the first time UDOT has usedcrack and seat. The Asphalt Instituteworked with UDOT staff to provide crackand seat specifications.

People

William C. Carey, Executive VicePresident of Southern States Asphalt Co.,Ashland Petroleum Company, is theAsphalt Institute’s 1997 Chairman of theBoard of Directors. Gene Chew,Managing Director, Sales and Supply, NesteTrifinery Petroleum Services, is theInstitute’s 1997 Vice Chairman of theBoard.

Dwight Walker, previously AsphaltBranch Manager for the KentuckyDepartment of Highways, is the AsphaltInstitute’s new Associate Director of Research. With more than 25 years ofexperience in asphalt design and materials,

he will be directing various Institute labora-tory projects, including a project on thetesting and inspection of asphalt overlays.

W. L. Hindermann, former managingengineer for the Asphalt Institute’sNorthern Division, recently passed away.Recognized by many as the “Father of Full-Depth Asphalt,” Hindy was the author of anumber of the Institute’s publications andpromotions on Full-Depth asphalt. He waspresident of the Association of AsphaltPaving Technologists, president of theMinnesota Society of ProfessionalEngineers, listed in the Asphalt Institute’sAward of Merit, and was inducted intoNAPA’s Hall of Fame in 1990. He wasesteemed by asphalt researchers, technolo-gists and contractors. “Hindy was a topengineer and a good administrator,” saysformer Asphalt Institute president GeneJohnson. “We will truly miss him.”

Carmela Chapelle, Engineering Research Technologist forthe Asphalt Institute, supervises Research Technician HeidiHope (left) of Conoco, Inc., at the recent Superpave BinderCourse held at the National Asphalt Training Center II(Asphalt Institute) in Lexington, Kentucky. Bruce Cline ofCITGO Asphalt Refining Co., Keith Friley of AshlandPetroleum Co., and Tom Hogan of Koch Materials also par-ticipated in the training.


by John Davis, Editor, Asphalt Magazine

When Stearns County HighwayEngineer Doug Weiszhaar wanted toreconstruct County State Aid Highway(CSAH) 75 with top performing pave-ment, he turned to Superpave.

Although he had heard that aSuperpave road would be durable andfree of premature maintenance, he didn’t know if such a road was eco-nomical or practical to build. Somepeople had told him that Superpavetechnology was too hi-tech and expen-sive for counties.

Undaunted, Weiszhaar invitedAsphalt Institute District Engineer AlPalmer to discuss the possible use ofSuperpave on CSAH 75 with him,Assistant County Engineer MitchAnderson and Senior Asphalt DesignTechnician Gene Thyen.

Palmer confirmed that Superpavetechnology would answer their con-cerns about the aging, cracking andrutting problems that recently appearedon some of the Stearns County roads.He recommended that at least oneSuperpave test section be included inthe CSAH 75 project, and that the sec-tion be build in a heavy traffic area.

Pre-Project PartneringSurprisingly, the Stearns County engi-neers not only agreed with his recom-mendation but suggested doing theentire project with Superpave. They

had considered doing the project withportland cement concrete (pcc) but thehigher costs of pcc prohibited thatoption.

The county and the AsphaltInstitute met again in February 1996 tofurther discuss the project. This time,the group invited a number of addi-tional asphalt industry representatives.Since Superpave had not been usedlocally, and the county was operatingunder a fairly tight federal-aid budget,the group asked Koch Materials andMeridian Aggregates to supply materi-als for a preliminary mix design to giveStearns County engineers an idea ofSuperpave material requirements andassociated costs.

New TechnologyAlthough the county like the idea ofconstructing CSAH 75 with Superpave,

they were concerned about the possi-ble higher cost of the new technology.Would the higher cost of Superpavematerials--aggregate, PG binder andtesting procedures--be prohibitive? Ifthe cost of using Superpave was toohigh, the county would have to chooseconventional materials and standarddesign.

Surprisingly, Stearns County engi-neers found that Superpave costs werecomparable to conventional pavingmaterials. In neighboring states, theuse of modified asphalt binders hadincreased costs substantially--as muchas $100 per ton. Although the PGbinder grade for CSAH 75 was stillundetermined, the PG could range

Stearns County Turns to Superpavefor Performance and Durability

ASPHALT 7Winter 1997

from 52-28 to a 58-40, depending onthe binder selection criteria used fordesign.

Even though very high qualityaggregates were used for the prelimi-nary mix design work, aggregate costswere competitive. Weiszhaar andPalmer asked the MnDOT researchoffice if any funding was available forconstructing Superpave research pro-jects at the local level. They said thatresearch money was available fromFHWA to investigate the use of poly-mer modified asphalt materials inMinnesota. Thus, a PG 58-34 asphaltgrade was selected for use on the pro-ject. Based on the locally availableasphalt materials, it was understoodthat this would result in a polymer-modified asphalt binder being used onthe project. The cost of the polymer-modified was offset by the researchmoney contributed by MnDOT andFHWA.

Superpave DesignPalmer and Stearns County considered

the project a real breakthrough forSuperpave in Minnesota. The newtechnology had not been widely usedin the state and CSAH 75 provided theideal forum to promote its use. TheCounty, MnDOT and FHWA decidedthat Superpave criteria would be usedfor the entire project.

Materials selection and mix designcriteria were strictly followed. Palmerworked with the county, materials sup-pliers, MnDOT research and theMnDOT central lab to provide prelimi-nary mix designs, and to develop plansand specifications for the Superpavesections. MnDOT did most of the mixdesign work and the University ofMinnesota helped with the aggregatetesting.

Specific Aggregate SourceThe county decided to designate a spe-

(from left) Asphalt Institute District Engineer AlPalmer, Stearns County Highway Engineer DougWeiszhaar, Senior Asphalt Design TechnicianGene Thyen, and Assistant County HighwayEngineer Mitch Anderson gather in front of anantique grader at Stearns County HighwayDepartment.

cific aggregate source for theSuperpave mixes and provide the mixdesign to all prospective bidders. Thiswas done due to a relatively short timespan for completing the project. Also,this would allow for an objective evalu-ation of the Superpave sections.

Through a cooperative agreementbetween the county and MeridianAggregates, the county was assuredthat all Superpave bids would be basedon the same aggregate selection andthe same aggregate price. Meridianand Palmer worked on the aggregateblends to achieve proper Superpavecriteria. No special aggregate process-ing was required for the formulation ofthe Superpave aggregate. All of theaggregates proposed for the blendswere currently available at the quarry.MnDOT validated these in the mixdesign phase.

MnDOT completed the mix designin July and sent materials to the AsphaltInstitute in Lexington, Kentucky, formix design verification. The mixdesign verification testing showed avery close correlation between theMnDOT laboratory and the Institutelab. A single mixture was used for allSuperpave sections on the project.

Typical SectionThe primary Superpave sections weredesigned to be in the westbound lanesof CSAH 75. The typical section forthese lanes included a base courselayer followed by an intermediatecourse and a wearing surface layer.The entire base course layer wasdesigned for a conventional MnDOTmix. The binder layer in the easternhalf of the project included Superpave


mix, while the other half was pavedwith a conventional mix. The entiresurface layer in the westbound laneswas then designed for Superpave mix.

A typical section included approxi-mately 5 inches of existing aggregatebase, 2.5 inches of 3/4-inch maximumsize, recycled hot-mix base course, 2inches of 3/4-inch maximum size inter-mediate course mix, and 2 inches ofsurface course mix. The Superpavemix used for the intermediate and sur-face layers was 19mm nominal size; theconventional intermediate course mixconsisted of 3/4-inch maximum sizeaggregate.

The surface course in the east-bound lanes consisted of 1/2-inch max-imum size aggregate meeting anMnDOT Type-47 specification, which isa minimum 70 percent plus #4 crushedwith 25 percent manufactured sand.The 10-foot-wide outside shoulderswere milled and paved with an overlaythat matched the thickness of thenewly constructed course.

ConstructionConstruction of the project began July30, 1996 and was completedSeptember 15, 1996. Construction onthe westbound and eastbound laneseach took three weeks. Actual con-struction of the three Superpave sec-tions in the westbound lanes took only4 1/2 days--August 26 to August 30.Duininck Brothers, Inc. of Prinsburg,Minnesota, was the contractor andJebro, Inc. of Sioux City, Iowa, sup-plied the PG 58-34 asphalt binder for

the Superpave sections.Eastbound lanes have conventional

MnDOT mixes except for a 1-mile sec-tion that contains Superpave aggregatematerials and 120/150 conventionalpenetration grade asphalt. The pur-pose of this section is to compare per-formance between the conventionalsections and the Superpave sectionscontaining PG binders in the west-bound lanes.

The contract specified milling outabout 6.5 inches of existing pavementin the westbound and eastbound trafficlanes of the 5.78-mile project. MnDOTspecifications allowed the contractor touse recycled asphalt pavement (RAP)in all pavement layers unless the spe-cial provisions exclude its use. StearnsCounty prohibited the use of RAP inthe surface layers on this project. The

contractor chose to use 50 percent RAPin the conventional base and interme-diate layers. Approximately 16,000tons of the 76,000-ton project was con-structed using the SBR polymer-modi-fied binder and Superpave mix design.

Quality Control TestingSuperpave did not specifically addressthe mix production control aspects ofconstruction, although Minnesota has


been working under a quality controlsystem for several years. “So wedevised a testing procedure for theSuperpave production portion of theproject,” says Palmer.

“Stearns County was one of the firstto adopt the QC/QA concept forasphalt mix production, and they want-ed to continue the practice on theSuperpave sections. We inserted theSuperpave testing equipment and pro-cedural requirements directly into thestandard MnDOT QC/QA specifica-tions. This answered concernsexpressed by some that Superpave didnot include adequate QC/QA proce-dures.”

The biggest hurdle to overcomewas the lack of available equipment inthe state to perform the testing. Thecontractor and the Asphalt Instituteworked together to leap the hurdle.Asphalt Institute Mix Technologist GaryIrvine transported a SuperpaveGyratory Compactor from Instituteheadquarters in Lexington, Kentucky,to conduct daily gyratory compactiontests on the Superpave mixes. Thecontractor performed maximum specif-ic gravity (Rice), sieve analysis, asphaltcontent and pavement density testing,and collected samples for gyratorycompaction.

One of the unique aspects of theproject was that plant production wasbased solely on the results of the gyra-tory samples. During the entireSuperpave mix production, no adjust-ments were required in asphalt contentor aggregate proportions to meet thespecified mix volumetric criteria.MnDOT conducted the gyratory com-paction for the Quality Assurance test-ing. The FHWA Superpave mobile lab,

which was in Minnesota at the time,also conducted tests on the plant-pro-duced mix.

No SegregationBefore construction started, there wassome concern that segregation wouldoccur in the Superpave mix. A stan-dard MnDOT mix is typically 65-75percent passing the No. 4 sieve. TheSuperpave mix design called for 40percent passing. But segregation didnot occur. Adequate asphalt contentand film thickness, along with the high-ly crushed aggregate resulted in little, ifany, segregation during construction.

The project density specificationsrequired the use of a pneumatic tiredroller for intermediate rolling passes.After a few passes, however, the con-tractor requested the use of steel-wheeled rollers because “pickup” onthe pneumatic tired-roller was an obvi-ous problem. Once the proper mixtemperature was determined for ade-quate compaction, the contractor wasable to achieve consistent density.

The county specified 40-foot-inter-val sawcut and sealing to relieve ther-mal cracking on each of the differentdesign sections throughout the project.This was done to compare the lowtemperature properties of the PGbinder materials to sections of pave-ment with conventional asphalt binderand the stress relief cuts.

Comparing Asphalt andConcreteAbutting the 5.78-mile Superpave pro-ject on the east end is a 1.6-mile stretchof new four-lane concrete. The twopavements have approximately thesame traffic volume and percentage ofheavy trucks. Stearns County andMnDOT researchers will have an idealopportunity to compare constructioncosts and material performance on thetwo projects.

Stearns County officials, MnDOT,FHWA, the contractor, the aggregateproducer and the Asphalt Institute allbelieve the project went smoothly andsuccessfully because of the cooperationin forming a plan, then workingtogether to bring it to fruition. StearnsCounty engineers are particularlyenthusiastic about the smooth execu-tion of the project and are anticipatinggood results. Still, they have questions.They want to know if:

▲Superpave will last longer and per-form better than conventional asphalt pavements.

▲Superpave will reduce thermal cracking.

▲Superpave will prevent the loss of fine aggregates and avert the need for an early sealcoat.

▲Superpave will prevent rutting underheavy traffic.

▲Superpave will prevent disintegra-tion in the wheel paths.

County engineers also want to knowhow long a Superpave pavement canlast without an overlay, and how longit can last until it requires some form ofroutine maintenance.

Regardless of the unansweredquestions, Weiszhaar and StearnsCounty sees a bright future forSuperpave. “If it performs well, we’lluse it throughout the county,” he says.“We want to build roads that our cus-tomers appreciate. Our customers, themotorists, have been complaining late-ly because of less than excellent roadquality. If Superpave gives us betterquality, we’ll use it again and again.” ▲


Night Pavingwith Asphalt isthe Answer toRehabilitatingRunway atWorld’s BusiestAirportby Tim Murphy, District Engineer, AsphaltInstitute

How do you rehabilitate a run-way at the world’s busiest air-port? The answer is carefully,quickly, with asphalt and atnight.

There are some obvious reasons forthat. There’s no time during theday to schedule laydowns on a run-way at the world’s busiest airport.Consequently, the contractor mustdo the work at night. And evenwhen working at night, the contrac-tor doesn’t have many hours topave. Probably six at most.Usually, they can’t start paving untilmidnight. Then, if they don’t gettheir equipment completely off therunway by precisely 6 am the nextmorning, they’ll pay a heavy penal-ty--$10,000 or more.

Bob Hart, Senior ProjectEngineer with the Chicago office ofHNTB Corp., put it this way:“Because of the tight time frame atO’Hare and the huge penaltiesinvolved in keeping the runwayclosed too long, there was no otherway to rehabilitate the runway thanto do it at night and with asphalt.”HNTB has designed several rehabili-tation projects for some of thebusiest runways in the world. Thestructural overlay of the runway atO’Hare is one of their recent projects.

Experienced PaverThe overlay, which incorporatesSuperpave criteria, was done inconjunction with a substantialreworking of the lighting system forRunway 9R-27L. “There was somuch electrical work that the primecontractor was an electrician,” saysHart. Allied Asphalt of Chicago wasthe paving contractor.

Allied has many years of experi-ence in placing asphalt in theChicagoland area and handled theO’Hare project with little difficulty,


according to Allied PavingSuperintendent Bob Housholder.“We know what we’re doing out onthe runway because we’ve beeninvolved with similar airport projectsat O’Hare for many years,” saidHousholder.

Stringent SpecificationRunway 9R-27L was a bit different,however. It was designed to carryaircraft weights well in excess of60,000 pounds with tire pressuresgreater than 100 psi. Because of thetight time constraints, and in orderto meet the stringent asphalt mix-ture P-401 specification (modified),HNTB:

1. required a larger maximum aggregate size than usual;

2. demanded a 30 percent higher stability requirement than ever before, and;

3. specified an asphalt cement “which, as written, dictated sup-plying a binder with a grading equivalent to PG 76-22,” accord-ing to Asphalt Testing Lab’s Manager, Kevin Nelson.

The tough mixture requirementswere part of the challenge; gettingthe job done within specificationand on time was the other. “Theavailability of materials coupled withour past experiences at O’Hare ledus to develop a special type of mix-ture,” stated Glenn Anderson,Quality Control Manager for AlliedAsphalt. The special mix allowedAllied to place up to 2,500 tons ofmix per night during the pavingoperation, although many times therunway demand allowed only sixhours of paving per night.

Paving in EchelonIn order to ensure the maximumtonnage placement, especially whilepaving with the mainline mix, the

contractor operated with two paversin echelon, each placing 25-foot-wide mats. “The exceptionally wideplacement of the asphalt mix meantusing the big Barber-Greene pavers’hard-tail extensions,” saidHousholder. “The hard-tail exten-sions allowed each paver to placeasphalt mix in 25-foot widths.”Allied met every longitudinal jointrequirement set by the P-401 specifi-cation. Six vibratory rollers comingright behind the pavers compactedthe 50-foot-wide mats.

Again, the many years of run-way experience helped Alliedensure the proper placement ofover 48,600 tons of hot-mix asphalton this project. Housholder said hiscompany achieved the best produc-tion and placement when producingthe mix near 340oF. Placing andcompacting was done at 310oFwhenever possible. “You just don’tlet it cool much before you roll it,”he added. “The rollers come rightbehind the pavers.”

Mix DesignThe mix itself was designed usingMarshall 75-blow design. The airvoids level, Voids in MineralAggregate (VMA) and the VoidsFilled Aggregate (VFA) criteria allmet or exceeded Superpave recom-mendations. The aggregate struc-ture consisted of 3/4-inch top-sizematerial and a very high level ofmanufactured sand. Approximately75 percent of all material passingthe No. 8 sieve was manufactured.

This aggregate structure design,coupled with the aggregate materi-als supplied by Vulcan Materials,and the binder supplied by SenecaPetroleum, enabled Allied to com-pact the 310oF mat right behind thepaver. This allowed the airport toland flights almost immediately afterpaving. Both project and inspectionpersonnel said there were little or

no pavement indentations, even onthe nights when planes landed justminutes after opening the runway totraffic--proof that the mix performedbetter than most mixes specifiedunder the current P-401.

Although the binder is costingaround 10 percent higher than thetype specified for conventional mix-tures, the Department of Aviationand HNTB anticipate using the mixin the future. Production on theproject was not compromised evenwith several new specificationrequirements. Given the challengesinvolved, project team members feltthe project went smoothly. “Thereis plenty of experience out there toindicate that the new binder prod-ucts work,” says HNTB’s Hart, “so,collectively, we decided to just do it!”

Always On TimeAlthough paving contractor AlliedAsphalt had to push to begin pavingoperations on time every night andpush to end them on time the nextmorning, they did not pay costlypenalties. Paving equipment wascompletely off the runway by 6 amevery morning. If not, the AviationAdministration would have chargedAllied $10,000 for the first 15 minutedelay, then $5,000 more for any partof an additional 15 minute delay.

The big planes are rolling againon one of the world’s busiest run-ways--all night long and all daylong. And both HNTB and Alliedare ready to do it again on someother runway. “We always enjoythe challenge,” says Housholder,“especially if it’s different or hasn’tbeen done before. We learn some-thing new on every project. On thisone, we’re glad we didn’t hold uptraffic. We did a good job, but if wedo it again, we’ll probably do iteven better.” ▲


by Dr. Richard W. May,Director of TechnicalServices, Asphalt Institute

The Superpave sys-tem is the culmina-tion of five yearsand $50 million ofresearch effort inasphalt materials bythe StrategicHighway ResearchProgram (SHRP).The fast-trackresearch conductedunder SHRP wasunprecedented in itsscope and depth,and it has brought tothe highway indus-try many productsthat will improve theperformance anddurability of UnitedStates roads and tomake those roadssafer for bothmotorists and high-way workers.

However, aswith any massiveresearch effort, com-pleting the researchmeans that only halfthe work is done.Research productsmust be brought outof the laboratoryand used in thefield, and Superpaveis no different. Andas experience isgained during prod-uct implementation,new concerns andissues arise thatwere either not thescope of the originalresearch or havecome up as the newproduct is used.This is no differentwith Superpave.

The FederalHighwayAdministration(FHWA) has beentasked by Congressto direct the imple-

mentation of all of the SHRP researchresults. There are many entitiesinvolved in this vast implementationeffort and this article has been written tohighlight the status some of the pro-grams pertaining to Superpave, as wellas the various sources of information.

TWG and ETGsThe FHWA has formed two groups tomanage and assist in the ongoing evalu-ation of the various products developedby the SHRP research. A TechnicalWorking Group (TWG) oversees manyaspects of a specific subject area of theSHRP research. The Asphalt TWG man-ages the Superpave evaluation andimplementation. A TWG is supportedtechnically by various Expert TaskGroups (ETGs); the Binder ETG andMixtures ETG are two that work withthe Asphalt TWG.

There are two primary sources offunding now being used to investigatespecific ways to improve Superpave.The National Cooperative HighwayResearch Program (NCHRP) is fundedby the state transportation departmentsto conduct research of a national scope,and it funds research in all aspects ofhighway needs, including Superpave.The FHWA has included funding in itssecond National Asphalt Training Centercontract (NATC II) with the AsphaltInstitute to use national expertise ininvestigating Superpave concerns.

PG Asphalt BinderSuperpave represents a good directionfor the asphalt industry. The Superpavesystem includes a new PerformanceGraded (PG) asphalt binder specificationthat incorporates a number of new andadopted test procedures to measure thephysical properties over the completerange of the binder service life. The con-dition of the asphalt binder is simulatedat various stages of its service life. Thetest procedures evaluate the ability ofthe binder to do its part in preventingthe three critical distresses of asphaltpavements: rutting, fatigue cracking andlow temperature cracking.

The binder specification was themost complete part of Superpave whenImp

lement

ation

ofSup

erpave

the SHRP research was completed, andmost states will be using the PG gradingby January 1, 1997. Arkansas, Utah, andTexas have already implemented the PGgrading spec. The FHWA initiated andhas completed a pooled-fund purchaseproviding the first set of the PG testequipment for all the states, and muchof the industry is comfortable with thePG system. As with any new test orpiece of equipment, there are things thatare being refined and reevaluated; every-one has definitely learned as they usedthem.

Superpave BinderStudiesThe Binder ETG is investigating issuesrelated to the PG specification. Topicsthat the Binder ETG is exploring includevarious equipment concerns, such asthose related to different manufacturersusing different design approaches for“new” equipment. They are recom-mending more research to establish amethod of calculating low pavementtemperature. Currently it is assumed tobe equal to the air temperature, which isvery conservative. Through the FHWALong-Term Pavement Performance(LTPP) program, data is being collectedand new calculation methods are beingexplored.

One study has been initiated to fur-ther explore how various types of modi-fied asphalts fit into this system and howto establish mixing and compaction tem-peratures. The NCHRP has awardedProject 9-10 to the Institute and theNational Center for Asphalt Technology(NCAT) to investigate these materials. Inaddition, under the NATC II contract, theInstitute is comparing the behavior ofvarious types of modified PG 76-22binders. Also, everyone wants to knowthe repeatability and variability of the PGtest results to understand how to inter-pret differences in measurements.Several round-robin test programs areunderway to resolve this issue.

Even with all of the questions, thePG binder specification represents a sig-nificant improvement for the asphaltindustry over penetration, ductility, andviscosity measurements. The questions


will eventually be resolved. AI has been working with the

American Association of State Highwayand Transportation Officials (AASHTO)to develop a Standard Practice for anApproved Supplier Certification Systemfor Suppliers of Performance GradedAsphalt Binders, PP 26, which will facili-tate the overall implementation processfor both suppliers and agencies. Theprocedures included in PP 26 will helpensure that the binder used on a projectmeets the specified PG grade.

Superpave AsphaltMixture DesignSuperpave also includes a completely-revised asphalt mixture design andanalysis practice. To obtain specimensthat represent the actual pavement,SHRP developed the SuperpaveGyratory Compactor (SGC), adopting themost reasonable parameters from theFrench and Texas gyratory compactiondevices. The SGC slowly kneads themix together into a mass that has similarcomposition and aggregate orientationas found in the roadway. In mix design,the SGC specimen is used to evaluatethe proper volumetric proportioning ofthe asphalt, aggregate and air that makeup the mix.

Existing aggregate criteria and testprocedures have been adopted, by con-sensus, to provide a uniform method for

all agencies to select aggregate materialsfor different traffic levels and the depthof the layer in the pavement structure. Inthe only new step that is different fromcurrent practice, the desired blend ofaggregate stockpiles is selected from anumber of trial blends based on severalfactors, such as aggregate gradation con-trol points and a restricted zone. Thesegradation controls (see Figure 1) areintended to build an aggregate structureor skeleton that achieves a compromisethat will produce both a durable and astable asphalt mixture.

In trying to achieve consistency on anational level, SHRP adopted the 0.45

power chart, the ASTM D 3515 standardset of sieve sizes and control points toevaluate these trial blends. The restrict-ed zone was adopted to avoid mixesthat have too much fine sand material.These types of mixes have experiencedproblems many times in the past,exhibiting plastic flow behavior undertraffic.

Superpave GyratoryCompactorOne of the nicest features of the SGC isthat it provides additional data to evalu-ate the compactability of the laboratorymixture. By monitoring how the mixcompacts (see Figure 2) initially (Ni), aswell as after a maximum number ofgyrations (Nm), an indication of mixturebehavior is provided. The Institute andother organizations are investigating ifthe slope of the compaction curve willprovide some useful information.

As one might expect, there are vary-ing opinions over parts of this mixdesign framework. There is consider-able debate over the Fine AggregateAngularity (FAA) test and criteria and itsintent to reduce the amount of roundedsands in the mix. Several organizationsare investigating this issue.

Many people have questioned theuse of the restricted zone; as a guideline,this zone is intended to help engineers

Figure 1. Aggregate Gradation Controls in Superpave

Figure 2. The SGC allows the compactability of the mix to be evaluated


when working with unfamiliar aggre-gates. Much of the controversy woulddisappear if everyone would use practi-cal engineering judgment and rememberthat experience should always dictate.Good performing mixes that violate therestricted zone should not be aban-doned. However, if the engineer hashad bad experience or no experiencewith a blend of materials, the zoneshould be avoided. The Institute strong-ly recommends not only avoiding therestricted zone but also using gradationsthat fall below the restricted zone, espe-cially for heavy traffic.

In addition, there are a few questionsthat need to be answered concerning theprocedure used for measuring moisturesensitivity -- AASHTO T-283. The ques-tions include the size of the specimen(100 mm vs. 150 mm diameter) as wellas the aging process to be used (T-283vs. Superpave short-term aging).Regardless of these issues, AASHTO T-283 has been shown in several studies tobe the most consistently reasonablemethod for evaluating moisture suscepti-bility or detecting mixes in which thebinder will strip off the aggregate.Further study will be done under a con-

tract soon to be awarded by NCHRP.

Non-Conventional MixesMore work needs to be done for mixesother than conventional dense-gradedmixtures, such as open-graded mixes,stone matrix asphalt (SMA), and mixesthat contain a significant amount ofreclaimed asphalt pavement (RAP).NCHRP awarded Project 9-9 to NCATand the Institute to explore some of thequestions with non-conventional mixes.To answer some of the questions per-taining to RAP (e.g. blending binders,extractions, material variability, mix crite-ria), the FHWA has authorized some test-ing at the Institute under the NATC IIand NCHRP is soon to award a newcontract in this area.

In addition, under NATC II, theInstitute and the Heritage ResearchGroup are testing specimens cored fromin-place pavements to further investigatethe design number of gyrations (Nd)needed in the SGC to achieve 96 percentdensity or 4 percent air voids. Somebelieve that SHRP established too manydesign compaction levels (28) and it isknown that these levels were based onlimited data. Even though the current

Nd concept appears to be working wellbased on hundreds of already-construct-ed projects, the FHWA Mix ETG hasdirected that more work be done toreevaluate this issue.

FHWA has completed the initialpooled-fund purchase of the SGC, pro-viding the first device for all of thestates. According to FOCUS, the FHWAnewsletter that reports on the implemen-tation of SHRP technology, a majority ofstates constructed Superpave Mix Designprojects in 1996 (see Figure 3). Many ofthese states had previously constructedprojects and are close to usingSuperpave mix design on a routinebasis. The original goal established byFHWA for mix design implementationwas the year 2000.

Beyond volumetric mix design,Superpave Mix Analysis involves sophis-ticated testing of SGC-prepared speci-mens and computer software analysis toprocess the test results. The SuperpaveShear Tester (SST) and Indirect Tensiletester (IDT) are used to subject thesespecimens to various stress conditions tomeasure fundamental structural materialproperties that can then be used in vari-ous computer models to predict future

Figure 3. States (ingray) constructingSuperpave mixdesign projects in1996 (FOCUS).


performance. This is the ultimate goal ofSuperpave. If the modeling and testprocedures were verified and available,we would have a tool to explore variouscompromises and truly optimize the mixdesign for the specific traffic, climate,and structure of the specific project.

Because this goal is so important tothe asphalt industry, the Asphalt Institutehas done a lot of work in this area. Weperformed the first evaluation of the finalSHRP testing, modeling, and softwareframework, and provided the initial feed-back to FHWA. There are many ques-tions that need to be resolved beforeSuperpave Mix Analysis can be usedconfidently. However, two states(Arizona and Indiana) have partiallyimplemented mix analysis on an experi-mental basis. The Superpave MixAnalysis system is now being evaluatedunder an FHWA contract by theUniversity of Maryland. Basic changes inthe software have been identified andrecommendations for model improve-ment and change have been submitted.

To implement Superpave in the field,there is a great need for a process offield verification and quality control andassurance. NCHRP Project 9-7 wasawarded to Brent Rauhut Engineering,

Inc. soon after SHRP concluded toaddress these issues. The final report forthis work is due at the end of the year.

Superpave CentersFortunately, unlike in the past, there aremany forums available for both raisingissues and obtaining information. Aninteresting and innovative concept ofcooperation developed around SHRP.Based on the original Pacific Coast orga-nization, five Asphalt User-ProducerGroups, representing various parts ofthis country and Canada, have beenformed to work on and resolve thesekinds of problems. Their goal is foragencies, asphalt producers, and asphaltcontractors to reach practical solutionsfor all. FHWA has reestablished theNATC to provide training and on-sitefield assistance. Between the two NATC contracts at the Institute, one-week hands-on laboratory courses onboth Superpave Binder Testing andSuperpave Mix Design have been pro-vided to about 700 people.

In addition, FHWA has establishedfive Superpave Regional Centers (seeFigure 4), through initial seed fundingand loaned laboratory equipment.

These Centers are available to assiststates in their geographical regions withtraining, laboratory needs, or other ques-tions pertaining to Superpave.

Publications on Superpave are cur-rently available from many of thesesources. FHWA has printed publicationson binder testing and mix design. TheInstitute has developed Superpave man-uals, written in practical simplified for-mat, on Binder Testing (SP-1) and MixDesign (SP-2). The Institute is alsodeveloping detailed operation manualson specific testings hints and trou-bleshooting ideas. In addition, throughthe NATC II contract, AI and theSuperpave Regional Center at Austin aredeveloping National Highway Institute(NHI) course materials for the individu-als less interested in hands-on training.These courses will be taught at theSuperpave Regional Centers, beginningnext year.

The Superpave system does repre-sent a good direction for the asphaltindustry. We encourage everyone tostay in touch as the technology andasphalt pavement performance advancefurther in the future. ▲

Austin, TX

Reno,NV

Auburn,AL

StateCollege,

PA

West Lafayette,IN

Figure 4. NationalAsphalt TrainingCenter and the fiveSuperpave Centers.


by Alan Forsberg, Public Works Director andCounty Engineer, Blue Earth County, Minnesota

After many years of planning,designing and constructing roads andstreets in Blue Earth County,Minnesota, county engineers havedeveloped reliable, practical principlesfor building and maintaining low vol-ume roads in cold climates.

Blue Earth is located in south cen-tral Minnesota andgets extremely coldin the winter.Temperatures ofminus 20 to 30oF arecommon. TheCounty has 720miles of roadwayconsisting of minorand major collectorsand minor arterials.Traffic ranges fromas low as 100 vehi-cles per day to sev-eral thousand perday. About 400miles are paved.The rest are sur-faced with aggre-gate. Traffic in ruralparts of the countyis stable, but aroundthe City of Mankato,it is steadily grow-ing.

Decisions topave roads in BlueEarth County aregenerally based onpotential for eco-nomic develop-ment, maintenancecost, safety andenvironmental con-siderations such as

dust and erosion. Limited resourcesbalanced with demands for roadimprovements also influence deci-sions.

PavementDrainage

The County recognizes thecritical need for good drainage in

designing and constructing pave-ments. Slotted, corrugated drain tileand open-graded drainage layers areeconomical and effective. The 4-inchthick clean rock drainage layer underthe aggregate base provides drainagethrough the drain tile system. But thedrainage layer under the shoulder isnot necessary for proper drainage.

Base design that extends theaggregate base through and beyond

the shoulder costsmore and is unnec-essary because theshoulders get littleor no traffic. Itsadditional cost fordrainage or load-carrying capacity isnot warranted onmany low volumeroads.

DesignDec-isions

Because the climateis extremely cold inwinter in centralMinnesota andbecause traffic vol-ume is low in partsof the County, BlueEarth pavementengineers haveestablished that ourroad designs mustconsider the follow-ing factors:

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Practical Principles fo

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▲ roads fail because of age, or oxida-tion and stripping of asphalt binder;

▲ additional asphalt provides increased durability and a reservoir to compensate for oxidation and stripping;

▲ infrequent but heavy loads may cause failures;

▲ emphasis solely on ESALs may result in short pavement life;

▲ design is often a compromise between the current most eco-nomic design and future needs;

▲ road designs should focus on a 15- to 20-year design life.

Because of these factors, Blue EarthCounty engineers have found that arelatively high asphalt content coupledwith low air voids provides the elastic-ity needed for long pavement life withlow traffic volumes and extremeweather conditions. The Countyrequires an integrated design-constructmethod for asphalt pavements thatcontrols air voids appropriate for theparticular mix by varying gradation ofaggregates and asphalt cement.

Studies, coupled with our ownexperience, show that high air voidspromote pavement deterioration dueto oxidation and stripping. Problemsassociated with low voids such as rut-ting and bleeding are not common onlow volume roads.

Consequently, low volume roads,especially those with light traffic andlight loads, should be designed towardthe low end of the air voids spectrum.

DurableAggregates

Hard, durable aggregates,which will resist the affects of loadingand severe weather, are also essential.Critical aggregate qualities include gra-dation of material by size and hard-ness, shape and affinity for asphaltbinder. They effectively transfer loadsand reduce spalling. Crushed materialssubstantially increase stability andreduce rutting. The best gradationsare developed by requiring two ormore stockpiles graded by size.Coarser materials with increasedcrushed content are best. Limiting theuse of soft, deleterious materials willprevent surface spalling and increaselong-term stability.

When larger rock is not locallyavailable, imported material is an alter-native. The County requires an inte-grated design-construct method forasphalt pavements that controls airvoids appropriate for the particularmix by varying gradation of aggre-gates and asphalt binder.

MaximumDensityLine

A Colorado DOT study examined 101mix designs for relationships betweenair voids and several alternative maxi-mum density plots. The study foundthe maximum density line was a use-ful rule of thumb to determine how toadjust gradation to optimize the mix-ture’s air voids. If a local agencywants higher air voids, they will adjustthe gradation away from the maxi-mum density line. If they want lowerair voids, they will adjust the gradationtoward the maximum density line.

Blue Earth specifications allow thelocal agency to adjust asphalt contentand aggregate gradation upon request.This ability requires that the aggregateproducer have multiple stockpiles,and also separate pay items forasphalt binder and aggregate.

AdjustingBinder andGradation

Laboratory design is an essential butlimited model of the field environ-ment. The real need is to control airvoids, aggregate and asphalt binder inthe hot-mix asphalt produced at theplant. The following is an example.

Blue Earth County was paving aroad in the summer of 1993. LoveallConstruction was the contractor.Gradation and asphalt content testsshowed the contractor was operatingwithin the specifications, but samplesshowed that air voids at 5 percentwere above the optimum 3 to 4 per-cent for the low volume road.

An asphalt content of 6.5 percentwas appropriate based on past experi-ence with the aggregate source.Production gradation was extremelyclose to trial mix gradation. TheCounty elected to adjust the mix gra-dation since the asphalt content wasappropriate.

After studying the maximum densi-ty curve, the County instructed thecontractor to decrease the sand by 2percent increments. This would moveproduction gradation toward the maxi-mum density line and reduce the airvoids. A voids update was done aftereach increment until the contractorreached voids of 3.5 percent.Production then continued at 3.5 per-

or Low Volume Roads

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cent air voids and asphalt content at6.5 percent.

Compac-tion

Behind the paver, the mathas 15 to 20 percent air voids. Therollers will reduce that void content to8 percent or less of maximum theoret-ical specific gravity.

The County currently requires thecontractor to construct a control stripto determine the best rolling pattern toreach maximum density. The contrac-tor determines densities by means of aportable nuclear gauge. Compaction specifications require breakdown bysteel-wheeled roller, intermediaterolling by rubber-tired roller, and fin-ish rolling by a steel-wheeled roller.

OwnerResponsi-bility

Planning, design, construction andmaintenance of low volume asphaltroads is still an art, but is slowlyadvancing to a science. We havelearned a lot since we began pavingand maintaining roads in the county.We have made mistakes, and we havecorrected them. We are trying to fol-low and improve upon the practicalguidelines that we have developedover the years.

The owner, the County, must bewilling to take responsibility for thequality of the work performed. We,myself and the Blue Earth engineeringstaff, represent the people in BlueEarth County, and we willingly takethe responsibility for doing the jobright. ▲

“Higher asphalt content and lower air voids generally providesthe most durable low volume mix. We’ve been working onthat premise for many years. Then, we began getting informa-tion from Focus, the Asphalt Institute, TRB and the Local RoadResearch Board (LRRB) about Superpave. The LRRB is a localadvocacy group composed of State and local agencies dedicat-ed to improving pavement throughout our State.

“After studying the information about Superpave and asking alot of questions, I was ready to try a Superpave project on alow volume road. We did a 3.5-mile, 2-inch-thick overlay onCounty State Aid Highway (CSAH) 30 at Crystal Lake usingSuperpave mix design. The average daily traffic on the road isabout 130.

“Minnesota DOT brought in its mobile pavement laboratoryand designed the mix right at the aggregate pit. Because theSuperpave mix used a higher quality aggregate, and coarserthan local aggregates, we had to import aggregate. It cost a bitmore, but only $1,000 to $2,000 more per mile than our con-ventional mix. LLRB paid the cost overrun.

“Another Superpave project, CSAH 8, included a 5-mile newroad, composed of 12 inches of aggregate base and 3.5 inchesof Superpave mix placed in two courses, one 2-inch courseand one 1.5-inch course. We used a PG 52-34 binder. It costjust a little more than the standard MnDOT binder.

“On all these projects, we are building a base of knowledge.As we gain confidence, we’ll shift completely to Superpave.We are convinced it has the potential for dramaticallyimproved pavement performance at a reasonable cost.”

Comments by Alan Forsberg, Public Works Director, County Engineer for Blue Earth County,Minnesota

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Blue Earth GoesSuperpave


Quality Construction of Hot Mix Asphalt Pavement

This seminar is devoted to teaching therecommended practices for constructing ahigh quality hot mix asphalt pavement.Participants will be provided with anunderstanding of the materials used in hotmix asphalt; hot mix asphalt productionprocedures; preparing surfaces for paving;placement and compaction operations;and pavement acceptance criteria.Interactive participation and example prob-lems will help in providing a good learningenvironment.

Detroit, MI February 24-26, 1997Seattle, WA March 3-5, 1997Burbank, CA March 10-12, 1997St. Louis, MO March 17-19San Francisco, CA March 24-26, 1997Atlanta, GA March 24-26, 1997Woodbridge, NJ March 31- April 2, 1997Cleveland, OH April 7-9, 1997Houston, TX April 7-9, 1997Fort Lauderdale, FL April 7-9, 1997Marlboro, MA April 21-23, 1997Las Vegas, NV May 12-14, 1997

The Superpave Asphalt Mix Design System

This workshop is designed to provideparticipants with a working knowledgeof the Superpave asphalt mix designsystem. Comparisons are made betweenSuperpave and the older systems usedfor specifying asphalt binders and mix-tures. The proper use of the Superpavesystem is presented, and a discussionwill be held on the Superpave implemen-tation activities in each workshop locale.

Detroit, MI February 27, 1997Seattle, WA March 6, 1997Burbank, CA March 13, 1997St. Louis, MO March 20, 1997San Francisco, CA March 27, 1997Atlanta, GA March 27, 1997Woodbridge, NJ April 3, 1997Cleveland, OH April 10, 1997Houston, TX April 10, 1997Fort Lauderdale, FL April 10, 1997Marlboro, MA April 24, 1997Las Vegas, NV May 15, 1997

Spring SeminarsQuality Construction of Hot Mix AsphaltPavementRegistration Fee: $360 per personAgency Discount for 3 or more-$299 per per-son

The Superpave Asphalt Mix Design SystemRegistration Fee: $150 per person

Mail your completed registration form to:Seminar Coordinator, Asphalt InstituteP.O. Box 14052, Lexington, KY 40512-4052For more information, call (606) 288-4964 Fax your completed registration form to:Seminar Coordinator - (606) 288-4999E-mail address for registration:[email protected]

Seminar City

Seminar Date

(Please use photocopies for additional registra-tions)

Name

Title

Organization

Address

City State Zip

Phone Fax

Method of PaymentComplete the registration form and sendalong with a check (made payable to theAsphalt Institute) or provide suitable billinginformation. Invoices are sent after the sem-inar is completed. Master Card and Visaaccepted.

❑ Check ❑ Invoice (Purchase Order No. __________)❑ Master Card ❑ Visa

Card Account Number Exp. Date

Name as it appears on the card

Signature

Asphalt Institute Federal ID # (61-1148531)


Louisiana Asphalt PavementAssociation’s president, SteveStrickland, believes thatLouisiana’s asphalt industry isheaded in the right direction withthe new hot-mix specificationsnow being implemented. Theywere developed by a specifica-tions committee that includedasphalt industry people, acade-mia, FHWA, LouisianaTransportation Research Centerand the Louisiana Department ofTransportation and Development.“In my opinion,” says Strickland,“the new hot-mix specificationsshould be used in lieu of theStone Mastic Asphalt mixes. Thenew specifications are far moreeconomical and will extend thelife of the pavements as expect-ed.”

The Rocky Mountain RegionAsphalt Pavement EducationCenter is a partnership betweenthe Colorado DOT, FHWA andthe Colorado Asphalt Pavement

Association (CAPA). It offers pro-grams that provide everythingfrom basic information aboutasphalt pavement construction todetailed training in QC/QA labo-ratory tests and asphalt mixdesign. Part 2 of the Mix Designprogram includes instruction infabricating and evaluating proper-ties of test specimens usingequipment specific to both theMarshall and the Superpavemethods.

Dodge County, Wisconsin,Highway Commission; theWisconsin Asphalt PavementAssociation; Northeast Asphalt,Inc.; Payne and Dolan, Inc.; KochMaterials Company; CMICorporation; and MarquetteUniversity all combined to stagean In-Place Asphalt RehabilitationTechniques demonstration thispast fall. Over 250 peoplewatched four techniques--1.Milling and Relay of asphalt pave-ment; 2. Pulverizing and Relay of

asphalt pavement; 3. Cold in-place reclamation, EmulsionInjection; and 4. EuropeanTechnology/Foamed AsphaltInjection--demonstrated on a 5-mile project.

NAPA conditionally endorsed theNational Occupational Safety andHealth (NIOSH) draft guidelineson engineering controls for high-way pavers. The NIOSH propos-al includes requirements for theinstallation of engineering con-trols on all self-propelled asphaltpavers weighting 16,000 poundsor more built after July 1, 1997.The engineering controls mustvent at least 80 percent of theasphalt fumes away from workerson or near the equipment. TheNIOSH proposal would requireall older pavers weighing thesame to be retrofitted with engi-neering controls by July 1, 1999.

Michigan Asphalt PavementAssociation reports that fineaggregate angularity requirementsfor Superpave may have a signifi-cant impact on material selection,especially on higher traffic vol-ume projects. MAPA urges theircontractors to obtain the requiredtesting equipment and begin test-ing their fine aggregates to deter-mine if they meet Superpave fineangularity requirements. MAPAalso suggests that contractorswork with aggregate suppliersand alert them about any neces-sary changes.

N E W SSAPAE

Winter 1997

Flexible Pavements Inc. ofOhio reports that Ohio DOT hasadopted a policy for 1997 hot-mixasphalt projects that require theaddition of SBR or SBS polymersto heavy duty surface courses. FPIrecommended the policy toODOT to increase durability andlongevity of its heavy-duty surface

mix. ODOT has put together ateam to implement the policy.The team includes representativesfrom liquid asphalt suppliers andthe hot-mix industry, as well asrepresentatives of polymer-modi-fied asphalt suppliers. The imple-mentation team will recommendhow to merge the policy with the

adoption of performance gradedasphalt binders, which will occurabout the same time.

Wayne Muri, Miissouri AsphaltPavement Association executivedirector, was awarded the GeorgeS. Bartlett award at the AASHTOannual meeting in Buffalo, NewYork. Muri earned the award inrecognition of his contribution tohighway progress. The award isco-sponsored by the ARTBA, TRBand AASHTO.

Maryland Asphalt Association,Inc.’s partnering team, composedof contractors and MAA executivedirector Brian Dolan, regularlymeets with the Maryland StateHighway Administration to edu-cate front line employees of boththe SHA and the asphalt industryabout new developments andnew ways of doing business inthe asphalt industry. Recentmeetings have included a presen-tation by the Plant Rating Team toensure that all employees under-stand the new plant rating system.

Carroll Lance, long-time execu-tive director of the AsphaltContractors Association of Florida,passed away in the fall of 1996.Carroll is rememberd by bothlocal and national contractors as a“warrior for the asphalt industry”and a strong supporter of NAPA.Jim Warren, formerly director ofeducation for ACAF, was recentlynamed its executive director. ▲

ASPHALT 21

Winter 199722 ASPHALT

SUPERPAVECENTERNEWSThe Federal HighwayAdministration helped establishfive Superpave Centers around theU.S. to serve as regional sources ofexpertise to promote the successfulimplementation of Superpave. Thefive Superpave Centers were estab-lished at Pennsylvania State Universityat State College, Pennsylvania; theNational Center for AsphaltTechnology at Auburn University inAlabama; Purdue University in WestLafayette, Indiana; University of Texasat Austin; and University of Nevada atReno.

The centers are involved in suchthings as ruggedness testing of theSuperpave Shear Tester (SST) and theIndirect Tensile Tester (IDT), SPS-9testing, mix designs and analysis forexperimental or pilot projects, foren-sic analysis, referee testing and profi-ciency testing. The centers are alsoan important source of hands-ontraining for engineers and techniciansat the local level.

The Southeast Superpave Center atNCAT serves eight states, Alabama,Georgia, North Carolina, SouthCarolina, Mississippi, Florida, Virginiaand Tennessee. The primary functionof the center is to support implemen-

tation of SHRP research results bystate DOTs and the asphalt industry inthe Southeast.

During the next fiscal year, the centerwill conduct seminars on mixtureanalysis procedures. It will provideproblem-solving expertise onSuperpave technology to the DOTsand the asphalt industry within theregion, as well as conduct a series ofround robin studies on modifiedbinders, unmodified binders and onthe Superpave Gyratory Compactor.The primary tools used by the centerwill the Superpave Shear Tester (SST)and the Indirect Tensile Tester (IDT).

The North Central SuperpaveCenter is working with states in itsregion to establish key concepts thatasphalt industry personnel need tolearn.One of its primary functions, as estab-lished by its steering committee, iscommunication. To that end, NCSCpublishes a quarterly newsletter andhas established a www site. Its homepage can be found athttp://ce.een.purdue.edu/~spave/.

At the request of the North CentralAsphalt User Producers Group, theNCSC has coordinated a binder roundrobin testing program to investigatethe amount of variation in binder test-ing from different labs under normaltesting conditions. This identified labresults and allowed comparison ofone lab with another. Test resultswere returned by 25 labs that tested26 sets of samples. Four asphalt cements, including one polymer-mod-ified binder, were tested for compli-ance with known grades in the rota-tional viscomter, bending beamrheometer (BBR) and dynamic shearrheometer (DSR).

The results revealed relatively highamounts of variation in some tests,which emphasized the need to follow

the standardized procedures closelyto eliminate sources of error.

The Superpave Center at Austinrepresents a unique partnershipamong TxDOT, FHWA, and theUniversity of Texas at Austin, Centerfor Transportation Research. Its mis-sion is to: 1. evaluate and improveSuperpave products through appliedresearch, 2. assist and promote uni-form Superpave technology, 3. be aninformation resource for managementlevel personnel, 4. provide training inSuperpave technology, and 5. pro-vide testing and technical assistanceto Superpave Center partners.

At its new location, the center’s labo-ratory contains virtually every labora-tory apparatus needed to conductSuperpave mix design and analysisand Superpave binder analysis.Because training is a key function ofthe center, the new site also containsa meeting room that will accommo-date thirty people in classroom style.The center also is located across thecorridor from the Asphalt andBituminous Sections of the TxDOTMaterials & Tests Division. TxDOTnot only supports the center financial-ly, but makes its equipment and per-sonnel available for applied researchaimed at implementing Superpave inTexas and in its partnering states.

Current activities at the WesternRegional Superpave Center includeequipment shakedown on SST, IDT,and additional binder equipment; set-ting up an additional laboratory fortraining purposes only with volumet-ric mix design and binder equipment;Superpave volumetric mix design andbinder training; developing trainingcourses for the specific needs ofneighboring states; forensic work forneighboring states using Superpavetechnology; materials characterizationof WesTrack binder and mixes; andpreliminary work on SST ruggednesstesting. ▲

Winter 1997 ASPHALT 23

ASPHALT INSTITUTE

Research Park DriveP.O. Box 14052

Lexington, KY 40512-4052

This publication is issued with the support of the Member Companies of the Asphalt Institute

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PAIDLEXINGTON, KYPERMIT NO. 1

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