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Expert Task Group on Asphalt Mixtures & Construction; Asphalt Binders; and Models Technology

September 11-12, 2000 Phoenix, Arizona

The meeting was convened on September 11, 2000 by Chairman Ron Sines of the New York Department of Transportation. Those members attending were:

Ron Sines, New York State DOT (Chair)
John R. Bukowski, FHWA (Secretary)
Frank Fee, Citgo (Vice-Chair)
John Cheever, Aggregate Industries, West Central Region
Ervin L. Dukatz, Mathy Construction Co
Kevin Hall, University of Arkansas
Gerry Huber, Heritage Research
Lon S. Ingram, Kansas DOT
Larry Michael, Maryland DOT
Julie Nodes, Arizona DOT
Randy West, APAC Inc
Mike Anderson, Asphalt Institute (liaison)
John D'Angelo, FHWA (liaison Binder ETG)
Eric Harm, Illinois DOT (liaison TRB Superpave Committee)
F. M. Harvey Wyoming DOT (liaison AASHTO Subcommittee on Materials)
Charles Marek, Vulcan Materials Co. (liaison National Stone Association)
Dave Newcomb, NAPA (liaison)
Haleem Tahir, AASHTO (liaison)

Ted Ferragut, TDC Partners (Support Staff)
Tom Harman, FHWA (Support Staff)

Those "friends of the ETG" attending were:

Dave Andrewski, Indiana DOT
Terry Arnold, TEXPAR Energy
Ken Brown, Troxler Laboratories
Tom Brovold, Test Quip
Joe Button, TTI/Texas A&M
Brad Cruea, Milestone Contractors
Frank Dalton, Pine Instrument Co.
Shay Emmons, Asphalt Institute
Khaled Galal, Indiana DOT
Lee Gallivan, FHWA Indiana Division
Fred Garrott, Illinois DOT
Joe Gundersen, Indiana DOT
David Jahn, Martin Marietta
Doug Hanson, NCAT
Richard Kim, NC State University
Brian Killingsworth, Fugro-BRE Inc.
Rebecca McDaniel, NC Superpave Center
George Merritt, Indiana DOT
Tony Ogle, Milestone Contractors
Jan Olek, NC Superpave Center
Charles Paugh, FHWA-SaLUT
Bob Peterson, Asphalt Institute
Murari Pradham, Utah DOT
Ali Regimand, Instrotec Inc.
Ryan Rizzo, FHWA Michigan Division
Geoff Rowe, ABATECH
Judie Ryan, Wisconsin DOT
Jim Scherocman, Consulting Engineer
Ayesha Shah, NC Superpave Center
Naga Shashidhar, FHWA-SaLUT
Greg Sholar, Florida DOT
Michael Smith, FHWA SRC
R.K. Smutzer, Indiana DOT
Pamela Turner, Asphalt Institute
Bill Vavrik, ERES Consultants
Chris Wagner, FHWA Indiana
Ron Walker, Indiana DOT
Jack Weigel, Payne & Dolan Inc.
Matthew Witczak, Arizona State University

Call to Order (Sines)
Chairman Sines welcomed the group. The Chairman reviewed the agenda (Attachment A) and emphasized that the essential functions of the ETG are to (1) review research results, (2) address technology gaps, and (3) provide guidance for users of Superpave. Chairman Sines asked the attendees for self-introductions.

Special thanks was given to Lloyd Bandy, Executive Director of the Asphalt Pavement Association of Indiana, Gerald Huber, of Heritage Research, and Lee Gallivan, of the FHWA Indiana Division Office for their efforts in hosting this meeting.

Team Reports
At the last meeting, the ETG formed teams to provide technical monitoring of the FHWA Superpave mixture and aggregate related activities and to provide the TRB Superpave Committee a continuing assessment of the AASHTO/TRB funded activities being conducted by the FHWA. Each team acts in a similar manner to an NCHRP Project Panel by: commenting on the scope of work, providing technical input for FHWA consideration, coordinating presentation of deliverables to the ETG for deliberation, and recommending necessary action to the ETG.

Teams are as follows:

Team 1, review of projects 90-01, 90-03, and 90-05, members include Tim Aschenbrener (team lead), Ron Sines, John Cheever, Kevin Hall, and John D'Angelo (FHWA Lead). A summary of the projects and their objectives is as follows:

  • 90-01 "Demonstration Project 90: Advanced Asphalt Mix Design and Field Quality Control" This project is a continuation of the FHWA's mobile testing laboratory which provides data for equipment validation and field control. This effort has previously produced considerable data for the ETG's consideration/recommendations. One ongoing study has been to access the variability of the ignition oven between laboratories and the effects of different types of aggregates and mineral dust has on the test result, especially that of hydrated lime. Hydrated lime can react with certain asphalts (see recent TRB paper by Prowell and Youcheff and result in a significantly lower asphalt content measured by the ignition oven which can be troublesome when quantities of hydrated lime fluctuate during construction. Project staff have begun efforts to evaluate the internal "mix strength" measuring device (shearing plates) for use with the Superpave Gyratory Compactor. Current work includes calibration and aspects of use as a quality control device. This work is in support of NCHRP 9-16, results will be reported to that project contractor (Asphalt Institute).

  • 90-03 "Superpave Mix Tenderness" This project is investigating mixture tenderness during compaction, especially as might be caused by moisture in the mix. Heritage Research and the Asphalt Institute are working with FHWA on this study. One aspect of this research is to develop a methodology to measure moisture in mixtures during production and laydown. Mixes have been produced with up to 2% moisture and are being evaluated for their effects on construction. This project is to be completed by end of 2001.

  • 90-05 "Fine Aggregate Specific Gravity Test" This project is developing a simple, repeatable fine aggregate specific gravity test based on a prototype device, developed by NCAT, that determines the aggregate's saturated surface dry weight. Error in determining the saturated surface dry condition of fine aggregate is thought to be the major source of error in the current fine aggregate specific gravity test procedure. Development of an improved test procedure is of particular importance because the fine aggregate specific gravity is use in the determination of the uncompacted void content of fine aggregate (the FAA) and mixture volumetric properties. Several commercial production versions are under development. The estimated cost is about $5,000.

Team 2, review of projects 90-07 and 90-09, members include Larry Michael (team lead), Rebecca McDonnell, Mike Anderson, Lon Ingram, Richard Stuart, and Tom Harman (FHWA Lead).

  • 90-07 "Understanding the Performance of Modified Binders" This project is an extension of TFHRC's polymer asphalt program (mix and binder specification development) which is determining if the MP-1 specification is blind to source of asphalt and/or method of modification. This effort will validate some of the NCHRP 9-10 project findings for modified binders. The FHWA's accelerated load facility is being used as part of this project.

  • 90-09 "Relating Mastic Test to Binder Performance" This research will investigate the relation of mastic components of asphalt mixtures to predict binder behavior in the mixture. Specifically the binder properties in combination with P200 material will be studied. Binder tests give a good prediction of the performance of neat binders, but work poorly for modified binders. Testing of mastics in this situation may provide a better correlation.

A copy of this presentation is contained in Attachment B and C.

Team 3, review of projects 90-06 and 90-08, members include Julie Nodes (team lead), Gerry Huber, Erv Dukatz, Frank Fee, and John Bukowski (FHWA Lead).

  • 90-06 "Ruggedness Testing of Superpave Shear Tester and Indirect Tensile Tester" Ruggedness testing of the Superpave shear tester (SST) and indirect tensile tester (IDT) has been conducted in accordance with established AASHTO procedures by the Superpave Regional Centers and the FHWA's TFHRC with the assistance of the Asphalt Institute. The results of this recent study have produced recommended procedural refinements of TP7 (SST) and TP9 (IDT). This effort has been completed and revised procedures presented to the ETG and referral to AASHTO. All efforts concluded by end of 2000, additional copies of the ruggedness reports are available from the Asphalt Institute. A copy of this presentation is contained in Attachment D.

  • 90-08 "National Superpave Conference (Forum 2000)" A national Superpave conference was held in Denver, Colorado in April 2000. Some 400+ attendees and 25 exhibitors were at the three-day conference. Proceedings of the conference were distributed on CD ROM to the attendees.

Activities reviewed by this team, 90-06 and 90-08 have now been completed.

Report Binder ETG Activities/Issues (D'Angelo)
John D'Angelo reported on the Binder ETG activities. The Binder ETG is:

  • Examining feasibility of controlling operational temperature of the rotational viscometer to greater tolerances to allow for determination of mixture and compaction temperatures for modified binders. A study will be conducted using 3 shear rates, 3 temperatures and 3 asphalts, it is anticipated that this work could be concluded prior to the next ETG meeting in April 2001.

  • Examining the repeatability of the equipment used to grade binder in the PG system. The variability of the DSR and the BBR has been much reduced. The procedure for the DT is being further refined.

  • Examining NCHRP 9-10 results for modified binders to verify the high temperature performance. The low temperature performance is being addressed by the new specification and DT equipment. The proposed MP1(a) specification will incorporate a critical low temperature cracking evaluation, with the BBR and DT. Using BBR results at two temperatures to create a master curve and then use DT to calculate the binder cracking temperature. Working with the FHWA's ALF to validate work performed under 90-07. The ETG reported good correlation between G*sinδ for neat binders but not for modified binders.

  • The RTFO is being further evaluated for use with modified asphalts. System using steel rods in conditioning bottles is being further examined.

Update Subcommittee on Material Issues (Harvey/Tahir)
This year a complete volume of all provisional standards was published and distributed. These included balloted changes to MP-2, PP-2, PP-28, and TP-4 (the Mixture & Aggregate ETG participated in the development of these revisions). Additional comments/clarifications to MP2 and PP28 will be provided to AASHTO by the end of the year. Also it is expected that wording to include the new RAP recommendations from NCHRP 9-12 will also be balloted at that time. TP-7(SST) ruggedness resulting recommendations will be balloted.

Issues still need to be addressed concerning laboratory mixture and compaction temperatures (Binder ETG activity), continuation of a fixed 4% air void target in mix design procedures, and establishment of possible separate VMA criteria for coarse and fine aggregates (NCHRP 9-25).

Additional proposed procedural specifications are being examined for use of infra-red cameras to detect potential segregation and measurement of surface texture using the ROSEAN.

The provisional standards to be released in 2001 will not be the full compilation of standards as in 2000, but rather will be an interim version containing only those standards that are new or that have been recently modified.

Attachment E contains a table of the various standards that the ETG has monitored as well as the various current/planned research efforts whose results will impact these standards. As needed, John Bukowski will maintain this table and provide updates and revisions of activities and deliverables. This information, as warranted, will be brought to the ETG attention for action and possible recommendations to AASHTO.

Impact of Raised Dust to Binder Ratio (West)
In a 1999 ballot the SOM moved to increase the dust-to-binder ratio to 1.6 for coarse graded mixtures. Several comments were received during the balloting process for this change. The SOM subsequently requested additional comment/input from the ETG regarding this issue. Since that time the ETG has been attempting to determine the original source of the dust-to-binder ratio requirement. In an effort to identify the current practice in the United States regarding this ratio, Randy West was asked to review existing literature on this subject and identify the various dust-to-binder ratio specifications in use by the States. A copy of the State survey is contained in Attachment F.

Based on his review Dr. West concluded the following:

  • Almost all research in this area indicates an interrelationship exists between the quantity and type of filler (P200 material) present in the HMA, which must be fully understood before impacts on HMA performance can be determined. Further, research has shown a wide range of mastic and mix properties can be observed for different dusts at constant dust-to-binder ratios. Therefore, establishing a meaningful generic specification for this ratio is difficult.

  • Of the 36 states responding to the ETG's survey nearly 45% have implemented a dust-to-binder ratio specification different than contained in AASHTO MP-2. The effects that filler has in asphalt binders and HMA are probably not well understood by most practitioners of this industry.

  • Because all fillers are not the same, the dust-to-binder ratio is a gross oversimplification of the effect of filler on HMA. The dust-to-binder ratio requirement should be replaced as soon as the industry implements an alternative method to evaluate dust within either the binder mastic or the complete mixture.

Based on this information the ETG recommends the following note be added to MP-2, Superpave Volumetric Mix Design:

"The effect of the filler on stiffening of the binder-dust mastic may be greatly oversimplified by the mass ratio of the dust and effective binder. Research through the past several decades clearly shows that characteristics of the dust (mineral filler) such as its particle size distribution, shape, and surface properties influences the dust's stiffening effect on the binder and performance of the mixture. Direct measurement of the stiffness of the binder-dust mastic should be considered for dust-to-binder ratios of 1.2 or greater."

AASHTO Standards Options (Hall)
The ETG established a Task Force (Hall, Cheever, Newcomb, Dukatz, Harm) to review AASHTO HMA test procedures associated with Superpave. Kevin Hall is leading this effort for the ETG. Dr. Hall reported initial review by this group indicated revisions to AASHTO T-209 appeared warranted. Recently, ASTM revised its version of this standard. The ASTM revisions, and the basis for them, will be considered by the Task Force in the development of any proposed revisions to T-209. Additionally, the Task Force will review AASHTO T-166 and T-283 for possible revision and provide the ETG a report of their findings.

VMA Properties (Anderson)
The Asphalt Institute has completed a recent study to do a quick overview of the influence of different VMA values on mix properties with coarse and fine aggregate gradations. There is continuing concern that fine and coarse gradation mixes should have separate VMA criteria. One observation of this effort was that coarse gradation mixtures with a high VMA value can be very sensitive, and small changes in gradation in some cases may adversely effect performance characteristics. Efforts to evaluate VMA criteria will continue under NCHRP 9-25. A copy of this presentation in contained in Attachment G.

Superpave Gyratory Compaction Calibration (Harman)
The FHWA is developing a device to be used with the Superpave gyratory compactor (SGC) that allows for a dynamic measurement of the gyration angle. It is essential that different gyratory compactors produce mixtures of similar results. Tom Harman made a presentation on this effort. A copy of this presentation is contained in Attachment H.

The ETG believes the need exists for an independent device that can validate the gyratory angle, which is applicable to all existing SGC devices. The current prototype device has been evaluated with several of the commonly used SGCs. The results obtained to date indicate additional work is needed to fully understand the results obtained from the device and how they should be utilized (i.e., what if any standard changes would be necessary). At this time it is apparent this internal angle verification device is not ready for use on a widespread basis. At the request of the FHWA the ETG formed a Team to work with the FHWA on the development of an experimental plan to fully evaluate this device. This Team consists of Gerry Huber (Team Lead), Mike Anderson, Erv Dukatz, Julie Nodes, and Larry Michael.

NCHRP 9-16 (Anderson)
Mike Anderson presented an update on the status of NCHRP 9-16 "Relationship Between Superpave Gyration Compaction Properties and Permanent Deformation of Pavement in Service." This project will determine if properties measurable by the SGC can be related to permanent deformation. This project will coordinate data and material with NCHRP 9-19. Anticipated completion date is the later part of 2001. A copy of this presentation is contained in Attachment I.

Pooled Fund Study 176 (Gallivan)
Lee Gallivan briefed the ETG on the contents of the draft final report of this national pooled fund to study effects of fine aggregate angularity, gradation and VMA on mixture performance. Five questions needed to be addressed by the research team: (1) Does the Superpave minimum VMA vs. NMAS relationship adequately define the threshold between stable & unstable mixes? (2) Is the Superpave minimum VMA vs. NMAS relationship independent of the FAA? (3) Is the Superpave minimum VMA vs. NMAS relationship independent of the shape of gradation? (4) What effect does FAA have on the performance otherwise identical mixes? (5) What effect does gradation (above, below maximum density line) have on performance of similar mixes? One initial finding, increases in FAA were found to improve performance. However, mixes produced with very high FAA did not necessarily perform better. A copy of this presentation is contained in Attachment J.

Multiple Ration Coarse Aggregate Analysis (Jahn)
David Jahn made a presentation on a simple device to measure multiple ratios of flat and elongated coarse aggregate particles. He maintains that such a range of values (5:1, 4:1, 3:1, 2:1) is much more descriptive of coarse aggregate than simply using a single number (5:1) as in the current practice. Video imaging can do the same thing, but at a much higher cost. This simpler device could also be a good tool to monitor aggregate changes during production. It was proposed that this subject would be recommended as a possible NCHRP research effort. A copy of this presentation is contained in Attachment K.

Simple Performance Tester (Witczak)
Dr. Matthew Witczak, of Arizona State University and principal investigator of NCHRP Project 9-19 briefed the ETG on status of activities to identify a simple performance tester. One of the critical topics in use of the Superpave system is the development of a simple performance test. Such a test is needed as part of the mixture design process. Superpave initially proposed several tests; the shear tester and the indirect tensile tester. While both devices are currently being used for research, they are not yet simple, quick nor practical for many mixture designs. Consequently, many agencies have turned to a variety of tests, including loaded wheel devices to augment their current mixture design practices. Other efforts to identify a mixture strength test include NCHRP 9-16 (SGC), 9-17 (Field shear test) and 9-18 (APA).

Research has been conducted by the FHWA and now by the NCHRP Project 9-19 to identify a possible simple performance test. This test needs to be relatively simple and low cost yet provide some fundamental mixture property. The proposed test is the determination of E* (dynamic modulus) using unconfined tri-axial loading. The test has been selected for further examination and validation. An additional test, measuring flow time-using static creep will also be included. Over the next 12 months, the 9-19 Contractor will further evaluate these tests. The ETG will review the recommendations from this work and make recommendations to the SOM on any proposed test procedures and criteria. The ETG will devote extensive time at its next meeting to this subject to prepare itself for future review of the products of this research. A copy of this presentation is contained in Attachment L.

Analysis of Asphalt Mixes & Aggregates Using Imaging (Massad)
Information was presented on current efforts at FHWA (D'Angelo) and Washington State University (Massad) to relate laboratory properties such ass air voids to in place pavements using x-ray tomography. Analysis further demonstrated the non-uniformity of air voids from top to bottom and side to side in a lab compacted specimen. Air voids distribution much different in field. Closet distribution of air voids in lab specimen to field cores is with a 50-75mm high specimen compacted at 1.5 degree angle. A copy of this presentation is contained in Attachment M.

Aggregate Issues & Needs (Marek)
The ETG reviewed the research recommendations presented in the "White Paper on Superpave Issues of Concern to the Aggregate Industry" principally prepared under the direction of Chuck Marek of Vulcan Materials Company. This paper was prepared at the request of the ETG to formally present the challenges faced by the Aggregate Industry in implementing the Superpave system. The paper identifies ongoing aggregate research, areas where additional research is needed, and activities the ETG could undertake to address aggregate industry areas of concern. In total 18 separate recommendations were suggested in the paper. These suggestions are grouped as either informational, regional issues, needed standard changes, or needed research.

A small group of ETG members (Lon Ingram, Eric Harm, Erv Dukatz, John Cheever, Gerry Huber, and Dave Newcomb) were asked to propose areas of needed research based on recommendations made in the White Paper considering the current research underway. This group suggested the following areas were of highest priority:

  • Conduct an NCHRP Synthesis on Aggregate research related to HMA performance
  • Evaluate VMA requirements with respect to aggregate grading
  • The influence of aggregate shape on mix performance, to include multiple ratio analysis and 3D imaging techniques
  • The effect of fillers on mix performance

During discussion the ETG agreed the NCHRP Synthesis should be completed, and the influence of aggregate shape on mix performance should also be researched. The ETG noted NCHRP 9-25 "Evaluation of VMA and VFA Requirements for Superpave Mixtures" is ongoing and should address the concerns raised regarding current VMA criteria. Additionally, the ETG took no action on the recommended standard changes at this time pending completion of the ongoing research in many of the areas recommended for change.

The ETG also noted SCOR will be reconsidering proposed research on the HMA moisture sensitivity test procedure AASHTO T-283. HMA moisture sensitivity analysis is a significant issue and the ETG strongly encourages SCOR to approve research directed at improving the existing method or to develop new test method.

Aggregate Gradation Optimization (Huber)
Aggregate gradation is a key to high performance pavement. The Superpave mixture design process requires the development and evaluation of three aggregate blends through a trial and error process. However, the Superpave system does not currently include a rational basis for selecting trial or alternate gradations. The ETG has discussed the "Bailey Method" as a possible approach to improve how mix gradations are determined. Robert Bailey of the Illinois DOT, developed this method of evaluating aggregate packing in a cooperative effort with the University of Illinois. Some ETG members believe a Bailey Method type-packing analysis is needed to improve how target gradations are established, especially as we move away from using the restricted zone and other similar limitations.

The concept of aggregate packing is not new. NCHRP project 9-8 investigated the idea of coarse aggregate packing for SMA. How much aggregate can be fit into a particular volume depends on the aggregate and how much energy is put into system. The process being proposed is relatively simple. Coarse aggregate is placed loosely into a known volume to determine the loose unit weight (the point when the coarse aggregate are just touching). Then coarse aggregate is rodded into the same volume to determine the maximum coarse aggregate unit weight (the point when the aggregates are packed as tightly as possible).

If the mixture is designed near the dry rodded unit weight limit, it is theorized the mixture will be difficult to compact in the field. The procedure also includes a similar assessment of the fine aggregate packing characteristics. Through a rational process the coarse and fine aggregate data are combined to give an estimate on the impact gradation changes will have on mixture volumetrics. This is a very basic overview of this procedure, which could be put into practice as part of the mixture design process to provide guidance on the selection of aggregate gradation.

Previously ETG members have volunteered to work with the Bailey Method in an effort to gain experience and provide insight into its potential application. Unfortunately, this effort has not been as successful as hoped. Gerry Huber, has volunteered to assist those members working with the Bailey Method through on-site training and technical support. The ETG members were asked to work with this procedure and report back at our next meeting.

Field Validation of Mixtures (D'Angelo)
John D'Angelo presented information on field management of asphalt mixtures. Aspects included mix verification, field monitoring and verification guidelines, and various statistical tools that can be utilized. The "decision tree" for various mix verification actions in the field was discussed. These materials have been developed as part of the FHWA mobile laboratory project (DP90) have been utilized for more than ten years on actual projects. John D'Angelo will provide ETG members a "Standard Practice for Field Verification of HMA" written in AASHTO format. A copy of this presentation is contained in Attachment N.

Results of NCHRP 9-12 Incorporation of RAP Into Superpave (McDaniel)
NCHRP Project 9-12, "Incorporation of RAP in the Superpave System" research has been completed. The research team has prepared recommended changes to AASHTO MP-2 and PP-28 to allow incorporation of RAP into Superpave HMA. A copy of this presentation is contained in Attachment O.

The ETG reviewed and concurred with the majority of the research team's recommended changes. However, the ETG recommends the binder selection guidelines for RAP use shown below be incorporated into MP-2 in-lieu of those proposed by the research team.

Recommended Virgin Asphalt Binder GradeRAP Percentage
No change in binder selection< 15%
Select virgin binder one grade softer than normal (i.e., select a PG 58-28 if a PG 64-22 would normally be used)15 - 25%
Follow recommendations from blending charts> 25%

The ETG was concerned that the research team's proposed binder selection guidelines were based on limited research and if implemented as proposed could adversely effect RAP use in the southwest. Additionally, the ETG recommends the note below be added to MP-2 to address the concerns targeted by the research team when developing their recommendations.

"Note: Research conducted as part of NCHRP 9-12 indicated that the high stiffness RAP (PG 88-4 after recovery) used in the study had a greater effect on the low temperature properties of the blended asphalt binder than the medium and low stiffness RAP (PG 82-16 and PG 82-22, respectively). This data suggests that the limiting RAP values in the Table may be modified depending on the low temperature stiffness of the recovered RAP binder. Refer to the NCHRP 9-12 Final Report for more details."

Nominal Mixture Size 4.75MM (Michael)
Maryland and Georgia are successfully using a mixture with a smaller nominal size that those normally designed with Superpave procedures. This mix contains a 4.75mm nominal size aggregate and is particularly useful in maintenance operations and for thin overlays. Larry Michael will prepare a proposal for changes to the AASHTO MP2 to include a 4.75mm nominal size mixture and submit the proposal to the ETG for discussion and recommendation.

FY2002 Research Statements (Ferragut)
Ted Ferragut reviewed the proposed FY2002 research statements that are to be considered by AASHTO. A copy is contained in Attachment P. These efforts are part of the Long Range 2005 Superpave Plan.

Development of material characterization models, design and performance models are a central theme in this plan. These models are complex, need to integrate with each other and require substantial resources. Attachment Q reflects a number of options that are available, the associated level of resources and impacts. Ferragut asked members to consider these and provide him with their input. With respect to the current delay in the development of the Superpave models the ETG suggests the 2002 Design Guide models be used on an interim basis while work continues on the development of the Superpave models. This will continue the movement towards our overall Superpave goals and the integration of mix design analysis, PRS and structural design while maintaining the national momentum in Superpave models research. The ETG recognizes this will extend the overall Superpave completion date to 2007 or beyond and adds considerable dollars to the original 2005 implementation plan estimate, however we believe it offers the best overall direction.

ETG meeting adjourned.
Next Mix Superpave Mixture & Aggregate ETG meeting will be held in Phoenix, Arizona. The meeting is currently planned to start at 8:00 am on April 3 and conclude at 3.30 PM on April 4, 2001.


  1. All presenters should forward electronic copy of their presentation to ETG Secretary. - All ETG

  2. Write a summary of findings on background of dust to asphalt ratio control and draft note for AASHTO specification(MP2) cautioning users that types of filler can have different impacts on mixture behavior. - West

  3. Review procedures and write recommendations for (a) simplified version of T209 based on the ASTM changes and (b) T283 as a result of NCHRP 9-13 study. Submit to ETG for consideration by 2/1/2001. - Hall

  4. SGC Angle Calibration Task Force, coordinate and develop with FHWA an experimental plan and report at next meeting. - Huber

  5. Provide prior to next meeting the results of research on mixing/compaction temperature determination procedures. - D'Angelo

  6. Update matrix of research activities, and potential impact on specifications being reviewed by ETG and schedule for input to AASHTO SOM, include dates and deliverables for each project. - Bukowski

  7. Produce a text version of presentation on field mix verification and develop in AASHTO format a recommended practice by 3/1/2001 for ETG action. - D'Angelo

  8. Members investigating the Bailey Method should provide their results to Huber for analysis prior to next meeting. If appropriate, the ETG will issue recommendations. - All/Huber

  9. Prepare a recommendation for changes to MP2 to include a 4.75 nominal maximum size mixture. Provide ETG Secretary for distribution prior to the next meeting. - Michael

  10. Prepare by 10/1/2000 a note for PP28, describing how to evaluate RAP based on low temperature binder properties for 3 levels of material. - Anderson

  11. Secretary will E-mail by 9/15/00 ETG members the options under consideration in the models program. Members should provide their recommendations to the Secretary by 10/1/2000. - All/Bukowski

  12. Prepare a problem statement for a TRB Synthesis on aggregate research (based on ETG Aggregate White Paper). - Bukowski/Ferragut

  13. Prepare a problem statement for NCHRP research on filler effects of mastic. - Harman/West

  14. Prepare a problem statement for NCHRP research on aggregate F&E multiple ratio measurements) and 3D imaging of shape as they relate to mixture performance. - Sines/Bukowski

Updated: 04/07/2011

United States Department of Transportation - Federal Highway Administration