FHWA Asphalt Mixture and Construction Expert Task Group (ETG)
May 11 - 12, 2006
The FHWA Asphalt Mixture and Construction ETG was convened on May 11 and 12 by Chairman Frank Fee and Co-Chairman Ray Bonaquist.
Those members of the ETG attending were:
|Frank Fee, Citgo Asphalt Refining Company (Chairman)|
|Ray Bonaquist, Advanced Asphalt Technologies, LLC (Co-Chairman)|
|John Bukowski, Federal Highway Administration (Secretary)|
|James A. Musselman, Florida DOT||Gerry Huber, Heritage Research Group|
|Kevin D. Hall, Univ. of Arkansas||Adam Hand, Granite Construction Inc.|
|John Haddock, Purdue University||Ervin L. Dukatz, Mathy Construction Co.|
|Judie Ryan, Wisconsin DOT||Todd A. Lynn, APAC, Inc.|
|Julie E. Nodes, Arizona DOT||Charles R. Marek, Vulcan Materials Co.|
|Cynthia LaFleur, Callanan Ind.||F. M. "Rick" Harvey, Wyoming DOT|
- Mark S. Buncher, Asphalt Institute
- David E. Newcomb, National Asphalt Pavement
- Randy West, National Center for Asphalt Technology
Not in Attendance
- Y. Richard Kim, North Carolina State University
- Eyad Masad, Texas A&M University
- R. Michael Anderson, Asphalt Institute
- Edward Harrigan, Transportation Research Board
Those "friends of the Mixture ETG" attending were:
|John D'Angelo, FHWA||Thomas P. Harman, FHWA|
|Cheryl Richter, FHWA||Nelson Gibson, FHWA|
|Katherine Petros, FHWA||Ernie Bastian, FHWA|
|Pamela Turner, NCAT||Robert James, APAC|
|John Cheever, Aggregate Industries||Peter Sebaaly, Univ. of Nevada|
|Patrick Kowing, FHWA||Richard May, Sem Material Group|
|Thomas Turner, WRI||Troy Pauli, WRI|
|Mike Harnsberger, WRI||Don Christensen, Advanced Asphalt Tech.|
|Jack Weigel, Payne & Dolan Inc.||Matthew Corrigan, FHWA|
|Jenelle Lewis, CITGO||Steve Mueller, FHWA|
|Tom Brovold, Testquip||Gaylon Baumgardner, PTSI|
|Mike Farrar, WRI||Raj Dongre, DLSI|
|Hussain Bahia, Univ. of Wisconsin||Scott Smith, WRI|
|Dale Decker, Dale Decker LCC|
Welcome and Introductions - Fee (Citgo Asphalt Refining Company)
Chairman Fee welcomed the group, and asked that all attendees record their contact information on the circulating sign-in sheet so that they may receive e-mails regarding the Mixture ETG (both friends and members). Copies of the meeting agenda were distributed. Self-introductions of all attendees were made.
Reformation of the ETG: Objective/Scope - Bukowski (FHWA) and Fee (Citgo Asphalt Refining Company) - Attachment 1
Secretary Bukowski stated that this ETG's focus was previously on Superpave, but now the scope is broader in that the focus is not just on Superpave, but also on asphalt mixtures and construction technology. Bukowski stated that according to federal mandates, discussion during the meeting should not result in the development of specific language for a contract statements of work or procurement actions.
Chairman Fee provided an overview of ground rules for the meeting, which included the following:
- A formal agenda will be established for each meeting. Friends of the committee are equal in regard to input. Input is welcome up to 2 weeks before each of the meetings.
- Notes/minutes will be posted online so that they are more readily available to all attendees. Please contact Frank Fee or John Bukowski about becoming a member.
- In regard to controversial issues, the ETG meeting serves as a discussion forum, these items will be recorded. The minutes/notes of the meeting will become the official input and will serve as a record of any recommendations.
- Comments and any possible changes in regard to the ETG discussions or composition are encouraged. Action items and information will be provided for possible action at a later date.
- Consensus recommendations have been a very useful tool, especially regarding controversial issues. These minutes will be forwarded to everyone for review and input, which will encourage consensus on issues.
- There are three asphalt related ETGs: Binders, Modeling, and Mixtures. A liaison will be developed between the ETGs. Liaisons will be responsible for providing input from this ETG to other ETGs.
- The unique addition to this Asphalt Mixture ETG now is the construction element. This ETG needs to work together as a unit to understand how all the pieces fit so that it can focus on what is really important. Each attendee is urged to bring their unique perspectives "to the table".
Review of Agenda and Action Items - Bukowski (FHWA) - Attachment 2
Secretary Bukowski presented on four issues that were worked on by different task groups from the previous Superpave Mixture ETG meeting held in July 2005. The following issues were presented during that meeting:
- Superpave Gyratory Compactor Issues: (a) Do we eliminate external angle measurement in T312, (b) Can we write specifications for the mixless measuring devices, (c) Review and publication of gyratory compaction operation guidance document. (All three issues will be discussed and moved forward for resolution later in this meeting.)
- TP62 for Determining Dynamic Modulus for HMA: A task group reviewed the TP62 specification and proposed changes (more involved areas such as master curve development may need separated document). A key issue that still remains is the TP62 test procedure and simple performance tester compatibility - there are still differences.
- Gyratory Compaction Ndesign and Locking Point: There are various methods on this emerging approach. Offers potential to enhance the Ndesign and specimen compaction during mix design.
- Compacted Aggregate Resistance Test: Advances in this and other aggregate related tests.
Internal Angle of Gyration for the Superpave Gyratory Compactor: Outstanding Issues - Hall (University of Arkansas) - Attachment 3
Kevin Hall presented an update on outstanding issues regarding the internal angle of gyration. Hall introduced the subject by providing an outline (technical issues and "where we are and where we need to go") and a brief history of the internal angle in the gyratory compactor. Hall provided a review of precision studies that have been performed and noted that reproducibility and repeatability are very important between devices and will alter the data (the ability of the device to measure an angle). Hall stated that it would be ideal, but may not be possible, to produce a single generic specification that would apply to all devices.
Hall touched on simulated loading, hot and cold issues regarding mold temperatures, and current status regarding specifications. Hall concluded his presentation by reporting that a draft of a document on gyratory compaction operation ("guidance document") has been written, which addresses such areas as cleanliness, mechanical wear, and conditions of the mold.
A lengthy discussion ensued during Hall's presentation in response to the question, "Where are we regarding the T312 specification?" Hall stated that T312 includes a Method B for internal gyratory angle measurement and refers to TP48, which is the only current AASHTO specification/acceptable method for measuring internal angle.
Further discussion took place on the following areas: (a) Do we eliminate external angle measurement in T312 (b) Can we write specifications for the mixless measuring devices (c) Review and publication of gyratory operation guidance document.
- Do we eliminate external angle measurement in T312?
- We have recognized the importance of the internal angle measurement, which has been included in T312. External measurement will probably have to be deleted - at some point we need to recommend that external angle measurement should be deleted. We need to come up with a better set of recommendations for an internal mixless solution - this is an issue that needs resolution. A procedure for mixless measurement needs to be included in AASHTO and a guidance document needs to be reviewed by all attendees and possibly published in some format.
- Would it be an option to put a note in the mixless method that says, "Let the agency select which device to use," whichever the device, and then everybody uses that device? This gives the State some flexibility. Another option is to just drop the angle criteria and say that the State is going to set up a mix and you're going to match that - I don't think we want to do that. A guidance document based on users/developers experience, would be especially useful. Every time we've had a difference in mixture specimen gravity during production, the main reason has been mold wear and poor equipment/maintenance. Problems with compactor angle differences appears to be less frequent a problem. The guidance document would solve the majority of all problems.
- The purpose of AASHTO standards for a common angle measurement is that it would be especially useful for work across multiple States.
- If you're not having a problem in your State, then why make a change to the internal angle?
- In the Southeast, some believe they can use external measurements and don't believe they have a problem.
- Nobody has actually pulled all data together to get a synthesis. This is needed, external versus internal measurements.
- The data we have seen on equipment shows that the external angle is not measuring the angle that pressure is applied to the specimen, only and internal angle can evaluate this
- Do we know that the external method for measuring an angle is invalid. This is independent from whether States have a problem or not. From data, yes it appears that measuring external angle approach is not correct, for a lot of reasons. It is clear that Method A should be taken out.
- We need to provide a new precision statement for the internal angle. This would help States move from external to internal measurement.
- Want to hear from other members - many believe we had covered this issue and gathered data. It's my opinion to drop the external angle - why do another study?
- We need to decide whether we're going to drop the external angle. Following manufacturer recommendations might force the use of Method B
- We should follow on one topic in order to keep focused. The question is, should we remove Method A from the standard? We have seen much data from numerous members that clearly shows that there is a major difference between compactors when calibrating using the external angle (Method A).
- If Method B is the only approach in T312, we will find a way to make it work. Part of it is cost issues. The need for standardization is crucial. The urgency to throw out Method A is dependent on the mixes used. From a State highway perspective, let's drop Method A if Method B is well established.
- Method B works. The question or issue pertains to using mixless devices. Mixless devices are now more available - this is why it is a current issue. A possible "Method C" could be added for mixless issues. The mixless measurement methodology still has concerns.
- That's the issue: If you drop Method A, you've got Method B, which is measuring internal with mix, whether to use a mixless device is completely another issue.
- Method B is solid - it works, but do you put mixless in at the same time as dropping Method A?
- A proposed method for internal angle measurement with a mixless device is needed. The issue is whether Method B is ready to take the place of Method A if it is dropped (internal measurement vs. external measurement).
- Rick Harvey: We need to give a reason for dropping Method A. There is some urgency here unless you want to put it off for another year. The AASHTO meeting that this will be acted on will be held in the first part of August, 2006.
- We have addressed the issue with external angle and we have an appropriate alternate to the DAV for internal angle (Method B). I don't know if we'll be ready to go forward with the mixless at this point, but that is a different issue.
- The specification for internal angle measurement may need to be changed from ±.02 to ±.03. ETG members are requested to provide comments to Kevin Hall.
- Another concern is that if we know that eventually we will use mixless internal angle measurement, shouldn't we wait to drop the external angle measurement. It would be disruptive to the States if we recommend dropping external and go to the DAV device and then in another year recommend mixless measurement of the internal angle. If we are sure the mixless measurement is going to eventually happen, we should just wait.
- Other members disagreed, two separate issues. Dropping the external angle should not wait until a final mixless measurement procedure.
- Secretary Bukowski: Suggested to go forward with a statement that the preferred method for T312 is the internal measurement and the rationale.
- Chairman Fee: We have an internal angle measuring device. There seems to be agreement that Method A is deficient. We need to provide a statement to AASHTO (Rick Harvey) for decision whether to drop Method A. The DAV appears to be the appropriate method to measure internal angle and use Method B in T312. While Method B is not as practical as it could be, it appears to be able to still provide a viable internal angle measurement.
ACTION: The ETG needs to write and send a statement to AASHTO for elimination of Method A from T312. Members and attendees should send data to Kevin Hall so that he can draft a statement for making the case to drop Method A. Chairman Fee noted that all attendees have the opportunity to give input. The statement and recommendation will be forwarded to AASHTO (Rick Harvey).
- Can we write specifications for the mixless measuring devices?
- To perform a internal angle measurement with mixless procedure, if we have a separate stand-alone standard for DAV (dynamic angle validator) with the HMS (hot mix simulator) and we have one for the RAM (rapid angle measurement device) in AASHTO standards - and T312 requires "calibrate using either DAV with mix/HMS or RAM according to manufacturer's recommendations," then the user would be using an AASHTO standard. This would still be using a device that has gone through some evaluation. So theoretically this could go through AASHTO and then have a standard for each individual measuring device; and not saying that the devices are interchangeable.
- That's a very important statement. The simulated loading devices (mixless measurement) do not appear to give the same results when used with different gyratories.
- I don't think you can write an AASHTO standard for a certain piece of manufacturer's device. It seems too complicated.
- I think there are ways around that. In regard to a generic description of machinery, you could put footnote in there "like such and such machine."
- Rick Harvey (liaison from AASHTO) commented that writing a standard for each of the devices is not an issue. In regard to putting a statement in T312, a warning could indicate that these devices are not interchangeable. Different devices will not give same answer.
- Mixless measurement and internal angle give us a tools to understand what the gyratories are doing. The industry will adapt to the standards that are provided.
- What we're talking about is the mixless device and the problems simulating mix. Is there still controversy over the data? I thought the issue was about internal angle. This, mixless devices, looks like an additional issue.
- We need to write an AASHTO standard for the RAM and for the HMS so that if an agency decides to implement T312 with a mixless measurement for internal angle, the standard to follow is available.
- I thought a proposed mixless standard still required work? Kevin Hall commented that only a generic specification for mixless internal angle measurement is ready.
- Hall and the task group will document mixless procedures, possibly a stand alone procedure for each piece of equipment (RAM and HMS in the DAV).
ACTION: Secretary Bukowski requested from Hall a statement for measurement of internal angle to be added within TP312 regarding use of mixless devices. When received, Bukowski will provide this statement to the attendees and to AASHTO, possibly to add it to T312 along with a recommended separate procedure for performing mixless, internal angle measurements.
- Review and publication of gyratory operation guidance document.
- The whole purpose of the mixless device development was to determine the differences between gyratories. The guidance document, currently in draft format, does a good job in leading you to a point so that you can eliminate the most common problems. The amount of mix in the mold changes the angles. I support the idea to keep this on a general standard basis, and encourage the development of a test procedure for a mixless devices that could be referenced in TP312. We need a tool so that when problems occur, and you've eliminated the obvious, when you check the angle in the gyratory, there is a procedure to follow.
- Rick Harvey: Do we want the guidance document as procedure in AASHTO? What does the ETG believe would be most useful? Do we want the guidance document published by the FHWA that serves as a reference; or is it sufficient if the document is available just through the minutes.
- Does the AASHTO technical section have an opinion whether it would be best referenced as white paper or best practice, or whether it should be made into an AASHTO practice.
ACTION: Secretary Bukowski requested Hall's draft guidance document be reviewed by members and attendees and provide comments directly to Hall so that a "stand-alone" document may be completed.
Additional gyratory issues:
Secretary Bukowski: We have been asked to determine if PP35 "Evaluation of Superpave Gyratory Compactors" is still viable. This procedure covers a method for evaluating the suitability of a new models of gyratory compactors to prepare specimens for T312 through a comparison to the original models (Pine and Troxler) gyratory compactors. It was intended that the Superpave Regional Centers would perform this comparison.
- It appears that this comparison analysis is no longer being performed by the Centers. There doesn't seem to be a whole lot of awareness of PP35 being used or even existing.
- We're giving PP35 too much credit. We have new gyratories being developed, and I don't know whether the procedure described in PP35 is robust even if Centers are available to do this testing. We are fooling ourselves thinking that if we keep PP35, it will perform a certain function.
- TP35 really has no purpose because comparing new equipment to originals is not valid nor is it happening. What may be needed is some type of new purchase equipment specification.
ACTION: Chairman Fee requested members and attendees to provide any additional comments and the ETG will move forward to AASHTO with a recommendation for possible deletion of PP35.
Determining Dynamic Modulus (E*) of Hot-Mix Asphalt - Requirements in Mechanistic - Empirical Design Guide (MEPDG) - Hall (University of Arkansas) - Attachment 5
Secretary Bukowski commented that there are two overlying issues to keep in mind during Hall's and Bonaquist's presentation as follows:
- The existing TP62 for calculating dynamic modulus has a lot of potential extraneous material that may need to be stand-alone procedures (e.g., master curve, specimen preparation, etc).
- The simple performance tester requirements are different than the TP62 current procedure. This is an issue regarding what recommendations are made resolving the final version of TP62.
Hall introduced his topic by stating that one recommendation from the respective task group was to have TP62 as a test method for determining dynamic modulus not specific to any one test device. Hall continued by providing an overview of the MEPDG as it uses the dynamic modulus and of the design guide three hierarchical levels of input. He discussed the applicability of TP62 to the MEPDG. TP62 currently includes sample preparation, tests, and calculations to use the data. Hall elaborated on TP62 master curve, and E* testing issues (how to calculate loading time; calculate E* and how to perform the test).
Simple Performance Test (SPT) System: National Cooperative Highway Research Program (NCHRP) Project 9-29 - Bonaquist (Advanced Asphalt Technologies, LLC)
Co-Chairman Ray Bonaquist provided an overview on Project 9-29 and the SPT system, and the dynamic modulus testing that can be done with the SPT. Comparing the SPT with the AASHTO TP62. Bonaquist emphasized that differences between the two due in part to changes/improvements in the SPT. Some of the equipment differences include, test temperature range, LVDT gauge length, allowable strain, conditioning cycle and specimen preparation-tolerances.
Chairman Fee: Do we have a written standard for the equipment and procedures based on the 9-29 work? Bonaquist commented that a product of the 9-29 effort is an equipment specification that contains: (a) Equipment specification (theories of test protocols from NCHRP 9-19), (b) Specimen preparation standard written in AASHTO format, and (c) Methodology for obtaining modulus master curves using SPT.
ACTION: Co-Chairman Bonaquist will summarize his presentation in a textual format so that it can be included in the minutes. This document will then be distributed more comment/input.
Discussion on TP62
- Should minor changes be made gradually to TP62 or wait for larger issues to be resolved? There are many existing improvements to this test procedure that need to be adopted by AASHTO. It is important to include these now. We can't wait for perfection.
- The Spring 2005 ETG changes to TP62 need to be incorporated by AASHTO.
- Secretary Bukowski: We have a two-page summary of the initial comments from the 2004/2005 task group. We have had several versions of the changes; they started to overlap, some had been forwarded to AASHTO. We also have additional significant future items such as separating out/calculating the modulus master curve.
ACTION: Secretary Bukowski will forward to Rick Harvey a copy of TP62 with proposed changes from 2004 and 2005 and attach a copy of this revised TP62 from the July 2005 ETG meeting to minutes.
- Chairman Fee: We have to move forward with some of the new proposed major changes. Can this be done quickly? Hall stated that some of the changes mentioned in these last two presentations are significant.
- The performance tester task group then needs to resolve; put these new items/changes into AASHTO format and distribute for ETG comment. Hopefully before the next meeting probably September. Want to have something for ETG review before the next meeting.
- Co-Chairman Bonaquist: This has to go back to the task group. The information from 9-29 and other procedures needs to be added. Co-Chairman Bonaquist, I can forward to Kevin the two standard practices, which deal with specimen preparation and dynamic modulus master curve generation. I think that Kevin has made a lot of these changes already, and what I've got here will supplement that. We're about 98% finished with the modulus ruggedness testing. The only part remaining is an equipment specification experiment. We will run the same materials in all three pieces of SPT equipment so that we give ourselves a comfort zone that we're not going to end up with some equipment uncertainties. I'm very confident that there won't be changes in appearance or major changes in the way the procedure is done.
- Chairman Fee: Are we looking at 6 to 8 weeks? Yes.
ACTION: Hall and Bonaquist are asked to send information/data on these new proposed changes to Eyad Masad, lead of TP62 task group. Other members are also asked to provide any input. Recommendations from the task group should be sent to ETG members for review prior to the next meeting.
NCHRP Project 9-33: A Mix Design Manual for HMA - Christensen (Advanced Asphalt Technologies, LLC) - Attachment 6
Don Christensen provided a progress report on NCHRP 9-33. Christensen provided an overview of performance issues, problems, predictions/volumetrics, tests and models (emphasizing that the performance models are useful but are only used for guidance, models are not the entire basis for the manual), HMA, mix design procedure, and review of current draft recommendations. Christensen then provided an overview of the manual itself (e.g., chapters, target audience, mix design tools) and concluded by stating that the mix design manual is still a work in progress. Christensen reported that it would be about a year before the final electronic version on CD is completed but that the manual will be completed sooner. Christensen emphasized that feedback is very much desired.
Chairman Fee: We have an early opportunity for everyone to look at this and to give feedback to the 9-33 researchers - this is an essential time for input.
WRI Consortium - Flexible Pavements Consortium - Harnsberger (WRI)
Mike Harnsberger presented on the need to develop new materials and test methods on the basis of sound fundamental science, not empirical testing, in response to increasing highway demands. Harnsberger showed that in regard to research funding by industry, only 8% of net sales are spent on research and development for highway systems. Harnsberger identified research needs and spoke of how a consortium of multi-disciplinary members with key contacts has been assembled to address these needs.
Two key areas of SAFETEA-LU funding were presented: Asphalt pavement research was divided into two separate areas: Fundamental Properties and Flexible Pavements. Research and Establishment of an Asphalt Research Consortium. Work elements have been established and assigned for research by the different consortium members. Harnsberger spoke about the research scope, which involves how fundamental science can be put into practice, and provided examples of fundamental research that has evolved into instruments more useful to the industry. Harnsberger indicated that information should flow between the various organizations and that work of the consortium will be presented to the ETGs.
WRI Consortium - Asphalt and Fatigue Behavior - Little (Texas Transportation Institute) - Attachment 8
Dallas Little presented on methods that can be used to analyze fatigue. He opened with four fatigue hypotheses and the different issues associated with each. He then discussed research objectives, focusing on the mix, mastic and the binder. Little indicated that dynamic mechanical analysis (DMA) is a good, quick, and reliable system to evaluate the fatigue life of wet and dry systems and the impact of healing and moisture damage. DMA can predict and evaluate healing potential, can quantify moisture, and can predict the lifecycle of the mastic. Little informed the group that calculating the dry bond strength between the asphalt and the aggregate gives an excellent indicator of moisture damage and is a fair predictor of fatigue life. That fracture law for viscoelastic materials is a key method for understanding fatigue behavior, the dynamic shear rheometer (DSR) can be used to identify the crack propagation potential within the binder itself, and adhesive and cohesive bond strengths can determine fatigue behavior. Little informed the group that the properties of the aggregate itself will influence stress distribution and expressed the need to develop component selection and binder guidelines for perpetual pavements.
WRI Consortium - Towards a Unified Physico-Chemical Model of Asphalt Binder - Pauli (WRI)
Troy Pauli provided an update on available items pertaining to asphalt mixtures, binders, and aggregates, and presented specifics of the work that has been performed to date in these areas. Pauli presented on the asphalt microstructure model and the asphalt solidification model, discussing such issues such as how to build an asphalt, the integrity of microstructures, thermodynamic qualities and changes as a function of time, thermal stability under slow crack growth, and energy dissipation effects.
Discussion Regarding Feedback on the WRI Consortium
- Chairman Fee: For the polyphosphoric acid [PPA] evaluation, are you going to try to get a wide range of binders? Pauli: Absolutely. We would like any ideas.
- Chairman Fee: We've been asked to try to participate in this effort guided by WRI. Many of these areas are interactive issues for us. These will be proposals funded by WRI Consortium work efforts. WRI has asked for us to provide input on this work.
- Dallas Little: We not only want, but we also need your comments to provide a meaningful proposal. This is not the work plan, more of a wish list to identify the type of work required.
WRI Consortium - High Performance Materials - Bonaquist (Advanced Asphalt Technologies, LLC) - Attachment 9
Co-Chairman Ray Bonaquist presented for Dr. Hussain Bahia (University of Wisconsin - Madison) on high performance materials. Bonaquist presented an overview on developing projects and described the details associated with these projects.
Chairman Fee informed the group that they will receive a written version and summary of the presentation from Bonaquist for review and feedback. Bonaquist mentioned that the issue of recyclable asphalt pavement was brought up in the Binder ETG, which is something that needs to be addressed.
Co-Chairman Ray Bonaquist posed the question, How can new things move from fundamental research to practice? Bonaquist stated that the idea of this research is to refine selected research products that are developed during study into useable tools. Bonaquist presented on the specific work elements in the area of technology development.
WRI Consortium - R&D Validation - Sebaaly (University of Nevada - Reno) - Attachment 10
Peter Sebaaly presented an introduction to research and development and validation. Sebaaly spoke of the AASHTO MEPDG, implementation assistance, how existing field sites will be monitored according to established specifications, and the plans to construct future field sites. Sebaaly discussed the technology transfer of the information gained in these areas and informed the group that there are training courses forecasted at the University of Nevada - Reno in January/February of 2007.
There was a comment that technology transfer is a two-way issue and that it should be defined for the States what they should be tracking in order to provide the correct data back to the WRI Consortium. States should be instructed what is expected. Afterward, there should be verification that States are capable of providing the data.
Chairman Fee again welcomed the group and indicated some changes to the agenda for the day.
An Approach for Characterizing High Reclaimed Asphalt Pavement (RAP) Mixtures - Bonaquist (Advanced Asphalt Technologies, LLC) - Attachment 11
Co-Chairman Ray Bonaquist provided an overview of work that has been done on high-RAP content mixtures, stemming from laboratory efforts that Advanced Asphalt Technologies has done for State DOTs (principally Maryland) and contractors to evaluate plant-produced mixtures in a RAP. High percentages of RAP can produce inadequate mixing of the materials. As a result, contractors began looking for ways to test plant-produced materials to determine the degree of mixing and to estimate an effective grade of the new binder to the mixture. Bonaquist presentation also included information on recycled asphalt shingles (RAS). Bonaquist reported on the various types of tests that were performed on mixtures (the dynamic modulus test was found to be effective in evaluating RAP and RAS mixtures) and on mix design, evaluation, and effective binder grades. Bonaquist summarized by indicating that there is a high interest in using much more RAP (the current design model assumes complete mixing of RAP) and that the mixture dynamic modeling test is a potential method of evaluating plant-produced mixtures.
Chairman Fee informed the group that at the past TRB annual meeting, there was agreement to move forward with a high-RAP research statement. Fee stated that the statement includes processing and characterization of RAP, and serves as a fundamental way of analyzing RAP mixes.
ACTION: Rick Harvey will present at the AASHTO subcommittee of materials meeting the RAP research statement members and seek support for the proposal.
Superpave Design Compaction Effort: Validity of Using Density at the End of Service Life as Parameter to Define N-Design - Huber (Heritage Research Group) - Attachment 12
Gerry Huber presented a report on locking points and discussed the gyratory history, N-design, locking point definitions, and the effect of gyratory compaction on mix design.
ACTION: Gerry Huber will lead an ETG task group, along with John D'Angelo, Tom Harman and Nelson Gibson (FHWA) to will determine develop a mission statement, and form a task group (recommendation for additional members) to work with the FHWA in evaluating locking point, N-design, and the influence of volumetrics.
Compacted Aggregate Resistance Test - Marek (Vulcan Materials Company) - Attachment 13
Chuck Marek provided a brief introduction and overview on the compacted aggregate resistance test and associated task force that was formed to look into developing a standardized test procedure and database.
The following activities were discussed:
- A white paper of the fine aggregate angularity (FA) test was developed, which was initially distributed to ETG members in August 2002. The aggregate task group felt that the FA angularity test in Superpave did not consistently identify angular cubical aggregates.
- A test procedure was developed; however, there continues to be considerable variability in the procedure, additional work is needed to standardize the procedure.
At this time, the aggregate task group can not make a recommendation for the ETG to adopt this test.
Kevin Hall suggested that he and Marek work together in an effort to rework the test data through alternate analysis procedures. Chairman Fee asked that a summary be attached to the data for enclosure in the minutes and that all related information be included in the report.
Institute for Aggregate Research: Evaluation of Fine Aggregate Characteristics and Their Relationship to HMA Performance - Williams (Iowa State University) - Attachment 14
Chris Williams provided an update on research done to determine which test best determines fine aggregate's effect on HMA performance. Although preliminary results have been attained, it is necessary to complete analysis d before a comparison among test can be made.
National Strategic Asphalt Plan Cheryl Richter - (FHWA) - Attachment 15
Cheryl Richter presented on plans to develop a asphalt research roadmap. This roadmap would be somewhat different in approach than the existing concrete roadmap. The concrete roadmap provided an extensive list of potential individual projects, the asphalt roadmap will focus on key areas and key topics. There will be a monitoring/ clearinghouse for the concrete roadmap, this is not planned for the asphalt roadmap.
New Items and Next Meeting Planning
- Emerging Technologies - At future meetings will there be intent to bring onto the agenda reports on new construction such as intelligent compaction? Yes, want discussions to be a reflection of current mix issues, also such as warm mix asphalt. Agenda items are up to the members.
- Restricted Zone - The restricted zone has been dropped from the Superpave criteria but it is used by some as a separator and to set density requirements of different mixes. Some mixes entering the restricted zone at the very tip; still define them as fine thus have to follow density practices for fine gradation even though would normally be considered a course mix. Maybe possible future meeting discussion.
- Recycling and the Binder ETG - The Binder ETG has recycling on their agenda. Isn't this a mixture issue? The action item from the recent Binder ETG is to use consortium to look at aging interactions, modified asphalts, basic binder fundamentals, and new ways to approach evaluation of binder during mixing/blending. This portion of recycling clearly has binder implications. Both ETGs intend to share information on the subject.
- ETG meeting minutes - Secretary Bukowski will circulate preliminary minutes to members and other attendees. Ask for review and additional comments. Next meeting of the Mix ETG, tentative date Monday 25th of September, possibly in the DC area.
Action Items - Summary
- ACTION: The ETG needs to write and send a statement to AASHTO for elimination of Method A from T312. Members and attendees should send data to Kevin Hall so that he can draft a statement for making the case to drop Method A. Chairman Fee noted that all attendees have the opportunity to give input. The statement and recommendation will be forwarded to AASHTO (Rick Harvey).
- ACTION: Secretary Bukowski requested from Hall a statement for measurement of internal angle to be added within TP312 regarding use of mixless devices. When received, Bukowski will provide this statement to the attendees and to AASHTO, possibly to add it to T312 along with a recommended separate procedure for performing mixless, internal angle measurements.
- ACTION: Secretary Bukowski requested Hall's draft guidance document be reviewed by members and attendees and provide comments directly to Hall so that a "stand-alone" document may be completed.
- ACTION: Chairman Fee requested members and attendees to provide any additional comments and the ETG will move forward to AASHTO with a recommendation for possible deletion of PP35.
- ACTION: Co-Chairman Bonaquist will summarize his presentation in a textual format so that it can be included in the minutes. This document will then be distributed more comment/input.
- ACTION: Secretary Bukowski will forward to Rick Harvey a copy of TP62 with proposed changes from 2004 and 2005 and attach a copy of this revised TP62 from the July 2005 ETG meeting to minutes.
- ACTION: Hall and Bonaquist are asked to send information/data on these new proposed changes to Eyad Masad, lead of TP62 task group. Other members are also asked to provide any input. Recommendations from the task group should be sent to ETG members for review prior to the next meeting.
- ACTION: Rick Harvey will present at the AASHTO subcommittee of materials meeting the RAP research statement members and seek support for the proposal.
- ACTION: Gerry Huber will lead an ETG task group, along with John D'Angelo, Tom Harman and Nelson Gibson (FHWA) to will determine develop a mission statement, and form a task group (recommendation for additional members) to work with the FHWA in evaluating locking point, N-design, and the influence of volumetrics.