Volume 4, Number 3 Spring 2005 Inside this issue Regional News NCAUPG Conducts Regional Round Robin . . . . . . . . . . . . . . . . . . 1 NCSC Moves into New Lab . . . . . . . . . 11 2005 Calendar of Events . . . . . . . . . . . 12 National News The Nature of Noise . . . . . . . . . . . . . . . . 3 Tire/Pavement Noise Measurement and Results . . . . . . . . . . . . . . . . . . . . . . . 3 Case Study: A Porous Friction Course for Noise . . . . . . . . . . . . . . . . . . . . . . 5 VMA: One Key to Mixture Performance 6 Top Down Cracking . . . . . . . . . . . . . . . . 8 A Tire/Pavement Noise Symposium: Quiet Asphalt 2005 . . . . . . . . . . . . . 10 Agencies and Industry Share Experiences, Best Practices . . . . . . . . . . . . . . . . . 10 NCSC Vision and Mission: To be a recognized source of hot mix asphalt expertise and to lead further development and implementation of hot mix asphalt and Superpave technology by providing services to its customers, through excellence in research, training and communication. Continued on Page 2 NCAUPG Conducts Regional Round Robin Rebecca S. McDaniel, North Central Superpave Center Since its inception in the early 1990’s, the North Central Asphalt User Producer Group (NCAUPG), has discussed working towards more uniformity in test methods across the region. Getting past the talking stage, though, has proven to be problematic. In 1996, Rich Wolters, of the Minnesota Asphalt Pavement Association, and Gerry Huber, of Heritage Research Group, reviewed the applicable AASHTO standards and rec- ommended ways to standardize the test methods by removing options. (Some methods allow multiple options, meaning states can rightly claim to be running the test according to AASHTO yet still have procedures that differ widely from those of neighboring states.) The recommendations were presented to the NCAUPG and forwarded to AASHTO for consideration, but were never implemented. Laird Weishahn, of the Nebraska Department of Roads, Mike Heitzman, of the Iowa DOT, and others in the region continued to try to make headway. However, with a reliance on volunteer efforts, infrequent meetings and the press of other work, these attempts could not get off the ground. The goal of standardizing test methods in the region remains a worthy one. Many contractors and material suppliers work in multiple states, meaning they have to test their materials differently depending on where they are sending them. Differing test methods also mean that personnel have to receive extensive training for certification in each state they work in, which represents a considerable investment in time and resources. The goal for the region is not to force all states to use the same specification limits, but rather to standardize many, if not most, of the test procedures. If common protocols are used, the required training should be the same though the specification limits may differ. This would facilitate reciprocity of training and certification between states on a wider basis. Training on the differences in state specification limits and operational procedures could be accomplished with a short review of state-specific material rather than a long, intensive, often repetitive certification course. Standardized testing procedures would also make it easier for states to share information about materials, construction methods, etc., and to learn from other states’ experiences.
NCSC Vision and Mission:To be a recognized source of hot mixasphalt expertise and to lead furtherdevelopment and implementation of hotmix asphalt and Superpave technology byproviding services to its customers,through excellence in research, training andcommunication.
Continued on Page 2
NCAUPG ConductsRegional Round RobinRebecca S. McDaniel, North Central Superpave Center
Since its inception in the early 1990’s, the North Central Asphalt User Producer Group(NCAUPG), has discussed working towards more uniformity in test methods across theregion. Getting past the talking stage, though, has proven to be problematic.
In 1996, Rich Wolters, of the Minnesota Asphalt Pavement Association, and GerryHuber, of Heritage Research Group, reviewed the applicable AASHTO standards and rec-ommended ways to standardize the test methods by removing options. (Some methodsallow multiple options, meaning states can rightly claim to be running the test accordingto AASHTO yet still have procedures that differ widely from those of neighboring states.)The recommendations were presented to the NCAUPG and forwarded to AASHTO forconsideration, but were never implemented.
Laird Weishahn, of the Nebraska Department of Roads, Mike Heitzman, of the Iowa DOT,and others in the region continued to try to make headway. However, with a reliance onvolunteer efforts, infrequent meetings and the press of other work, these attempts could notget off the ground.
The goal of standardizing test methods in the region remains a worthy one. Manycontractors and material suppliers work in multiple states, meaning they have to test theirmaterials differently depending on where they are sending them. Differing test methodsalso mean that personnel have to receive extensive training for certification in each statethey work in, which represents a considerable investment in time and resources.
The goal for the region is not to force all states to use the same specification limits, butrather to standardize many, if not most, of the test procedures. If common protocols areused, the required training should be the same though the specification limits may differ.This would facilitate reciprocity of training and certification between states on a widerbasis. Training on the differences in state specification limits and operational procedurescould be accomplished with a short review of state-specific material rather than a long,intensive, often repetitive certification course. Standardized testing procedures would alsomake it easier for states to share information about materials, construction methods, etc.,and to learn from other states’ experiences.
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Getting started on the road to standardizationpresents a number of hurdles. One big hurdlehas simply been the question: where to start?
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In January 2004, Erv Dukatz, Mathy Construc-tion Co., issued a proposal to the NCAUPG tore-focus attention on test standardization by out-lining a plan to help answer the question ofwhere to start. The proposal was to have eachstate in the region sample materials from oneor two projects and send them to each otherstate. The states would then test the materialsaccording to their own procedures and sendthe results to the North Central Superpave Cen-ter (NCSC) for analysis.
The concept was that the round robin testingwould help to identify which different test proto-cols produce meaningful differences in the re-sults. This information could then guide con-siderations of test standardization. If differencesin how we run a given test do not produce differ-ent results, that test might be one that could bemore easily standardized. States could modifythe procedures without changing specificationlimits or how they interpret the results. On theother hand, states might choose to retain theirmethods, but accept other state’s methods as well,since the answers are the same either way.
If significant differences in test results wereobserved, more investigation into the causes ofthese differences and an attempt to identify whichresults were “right” could be in order. Ultimatelythis could promote more standardization as wellas improved testing techniques for the region.
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In the end, six labs were able to participate in theround robin, testing nine different mixes fromaround the region. This represents a great dealof lab work over and above the routine workload.Several states realized at the outset that their lim-ited personnel and resources would not allowthem to take on such a large amount of work.The commitments and efforts of the Indiana, Iowa,Kansas, Nebraska and Wisconsin labs that didparticipate are greatly appreciated. The NCSClab also tested all of the materials in support ofthe experiment.
The nine mixtures tested represented a widerange of properties. There were three 9.5mm,three 12.5mm and three 19.0mm mixes. Thedesign traffic levels ranged from under 300,000to 40 million ESALs, with Ndesign values of 50,75, 96, 100, 109 and 125. (The Ndesign level touse was provided to each lab rather than having
labs use their standard, differing compaction lev-els.) The binder grades used included PG58-28, 64-22, 64-28, 70-28, 76-22 and 76-28.
Each lab tested the aggregates to determine:
♦ individual bulk specific gravities (if pos-sible using their test protocols),
♦ combined bulk specific gravity (measuredor calculated),
♦ fine aggregate angularity,
♦ coarse aggregate angularity or percentcrushed, and
♦ gradation of the design blend using givenstockpile percentages.
Each lab then prepared mixtures accordingto the given design and tested mixture proper-ties including:
♦ effective specific gravity,
♦ maximum theoretical specific gravity;
♦ bulk specific gravity at Ndesign (either mea-sured or backcalculated),
♦ air voids at Ndesign (measured orbackcalculated),
♦ Voids in the Mineral Aggregate (VMA),
♦ Voids Filled with Asphalt (VFA),
♦ density at Ndesign, and
♦ compacted sample weight and height.
Testing was completed and results weresent to the NCSC by mid-January. Analysis ofthe data is underway. A full report will beprepared this Spring and distributed to theNCAUPG Management Committee for consid-eration and action.
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Two primary factors have been considered in thedata analysis to date, Lab and Mixtures. That is,for a given set of test data, say the maximumspecific gravity (or Rice) data, the results wereanalyzed to see if there were significant differ-ences in the values for different mixes and ifthere were differences in the results from differ-ent laboratories. The results should be different
for different mixes; the analysis confirmed that,which adds confidence that the data and analy-sis are reasonable. The real question waswhether there would be significant differencesin the results from different labs when they testthe same materials.
The preliminary analysis of the data showssome interesting trends when comparing labs.For example, the aggregate test results were veryconsistent among the labs. No statistically sig-nificant differences have been identified in theresults of fine aggregate angularities or bulk spe-cific gravities. On the mix results, there were nosignificant differences in the maximum theoreti-cal specific gravity results. These may be testmethods where we can easily achieve standardiza-tion or accept the results of alternate test methods.
On the other hand, statistically significantdifferences were observed in the mixture bulkspecific gravities between the labs. Conse-quently, there were also significant differencesin the air voids, VMA and VFA. These differ-ences imply either a difference in the compac-tion of the specimens or in how the bulk gravi-ties were measured. Additional data analysis ison-going to investigate the possible explana-tions for these differences. Information on thetype of gyratory used, how it was calibrated,how the specimens were compacted (to Ndesignor Nmax), the short term aging procedure, mix-ing and compaction temperatures, test meth-ods and equations, and more, is being scruti-nized to see if there is any relationship to theobserved differences in test results.
It will unlikely that a single cause for the dif-ferences can be identified, but it is hoped thatthis exercise will help the region determine whereto go next. Perhaps a round robin exchange tomeasure the bulk specific gravity of compactedspecimens would be advisable. Or perhaps amore detailed investigation of gyratory compac-tion procedures will be needed.
After the final report is reviewed, the NCAUPGManagement Committee will be asked to deter-mine the next recommended step towards teststandardization. The first step taken with thisround robin will likely lead to additional stepsand more round robins. It is hoped that addi-tional labs, perhaps including contractors labs,will be able to participate in more focused, lessintensive follow-up studies.
The final report and information on futureefforts will be posted on the NCAUPG website athttp://bridge.ecn.purdue.edu/~spave/NCAUPG/Index.html, as it becomes available.
Getting started on theroad to standardizationleads to the big question:where to start?
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The NCSC has completed its move into new labspace provided by the Indiana Department ofTransportation. Attendees at the NCAUPG meet-ing in Lafayette in January toured the 17,000square foot addition to the INDOT Division ofResearch, which houses the main branch of theNCSC.
The new addition was formally dedicated inApril 2004, but it took several months after that tofinish installing and recalibrating the equipment.Months of planning and working with the architectallowed the design of the labs to facilitate the flowof materials from receiving, through sample prepa-ration and testing. Separate rooms are availablefor aggregate processing, binder testing, mixturesample preparation, mixture testing and cleaning.INDOT also has concrete testing facilities in thebuilding.
Work is now underway on remodeling theNCSC’s former lab and office space into a full suiteof offices. In addition to such amenities as carpet-ing and wall treatments, the new offices will pro-vide additional space for student and staff offices, awork/file room, conference room and more. Theprimary benefit of the new space, however, will be aquieter office environment, since the exhaust fans,hydraulics and refrigeration units associated withour lab tests have been moved into separate space.The NCSC staff has been temporarily displaced tomake way for the remodeling, but plans to moveback into the offices later this summer.
Tours of the facility are also planned for theupcoming Quiet Asphalt Conference/Workshop inNovember or can be arranged at any time by con-tacting the NCSC. We’d love to show you aroundand update you on our current activities any timeyou are in the area!
The National and Regional Superpave Newslettersare published three times a year and are coordi-nated by the North Central Superpave Center. TheNCSC is one of five Superpave Regional Centersestablished to assist with implementation of theSuperpave performance-based system for design-ing asphalt pavements. The NCSC is a joint effortof Purdue University, the Indiana Department ofTransportation, and the Federal Highway Adminis-tration and is administered by the Joint Transporta-tion Research Program at Purdue University.
2005 Calendar of EventsApril 19-20 ��������������� ����������������������������� ����������������
Soaring Eagle Casino and Resort, Mt. Pleasant, MichiganWebsite: www.miasphalt.com/
Dec 6-8 ��������������� �����������������%�&�� �'����$�����������������������Radisson Hotel and Conference Center, Plymouth, MNWebsite: www.asphaltisbest.com/calendar.asp
Jan 10-12 (�������������������)��* ��$�����+��������������"��,��2006 ��$�������-�����������������
St. Louis, MOWebsite: http://bridge.ecn.purdue.edu/~spave/NCAUPG/Index.html
