AASHTO Joint Task Force on Pavements

Meeting Minutes

November 12 and 13, 2002

Myrtle Beach, SC

·Agenda

·Minutes of the November 12 and 13, 2002 Meeting

·Attendance list

·List of Attachments (available at ftp://fhwaftp.fhwa.dot.gov)

·NAPA perspective.ppt

·ACPA perspective.ppt

·Development of a High-Speed Deflectometer.ppt

·2002 Flexible Pavt.pdf

·NCHRP Pavement Research: An Overview

1

Joint Task Force on Pavements

November 12-13, 2002

AGENDA

November 12

1:00 – 1:30 p.m.Introductions and WelcomeGary Sharpe

1:30 – 2:15 p.m.NAPA Perspective David Newcomb

2:15 – 3:00 p.m.ACPA PerspectiveGerry Voigt

3:00 – 3:15 p.m.Break

3:15 – 3:45 p.m.NCHRP Pavement Research OverviewAmir Hanna

3:45 – 4:15 p.m.AASHTO Overview Ken Kobetsky

4:15 – 4:35 p.m.FHWA Items Tommy Beatty 4:35 – 5:00 p.m. Rolling Wheel Deflectometer Max Grogg

5:00 – 7:00 p.m.Dinner on Own

7:00 – 8:30 p.m.Demonstration of 2002 Design Guide

November 13

7:00 – 9:45 a.m.Demonstration on 2002 Guide

9:45 – 10:00 a.m.Break

10:00 – 11:30 a.m.Demonstration on 2002 Guide

11:30 – 12:45 a.m.Lunch

12:45 – 2:30 p.m.Demonstration on 2002 Guide

2:30 – 2:50 p.m.Break

2:50 – 4:00 p.m.Closed Session

Task Force members plan to adjourn no later than 4:00p.m.

1

AASHTO Joint Task Force on Pavements

November 12 and 13, 2002

Myrtle Beach, SC

MINUTES

Opening remarks by Gary Sharpe

AASHTO adopted a reauthorization policy that is larger than TEA-21 level. The policy also includes an increase for research and $20 M/yr for LTPP. No comments were added to the minutes of the last meeting.

FHWA Update: Tommy Beatty

Tommy Beatty started by talking about a few FHWA items that relate to the JTF on Pavements: reauthorization, restructuring of the ResourceCenters, and the Concrete Earmark. He spoke about the status of each of the concrete projects under the earmark and gave an update on the Resource Centers. The resources centers will go through restructuring with a long-range plan for consolidation into one unified center. Any interested party can obtain a copy of the concrete earmark projects from Tommy Beatty.

AASHTO Update: Ken Kobetsky

Ken Kobetsky from AASHTO also talked about AASHTO’s reauthorization. Some of the sectors that were discussed were safety, working with the environment, motor carrier security, operations, asset management, needs for rural roads, capacity, system preservation, alternative fuel sources, congestion relief, and funding for transportation enhancements (e.g., bike paths). They would also like to improve environmental streamlining through the Center for Environmental Excellence. AASHTO is proposing to use innovative techniques for funding and investments. One effort is to leverage funds though a transportation financing corporation.

All of the information is included on the website: transportation.org on the reauthorization link.

He also discussed the idea that the JTF on pavements should expand to include a few liaisons from the Subcommittee on Materials. Two other subcommittees that they want to reach out to would be Planning and Aviation (FAA). In return, the JTF will have a report given at other subcommittee meetings as a liaison from the Pavements side.

He announced that the Subcommittee on Design will hold a meeting around June 13 to 16, 2003, in Boston. Also, the Subcommittee on Maintenance recently submitted a glossary on pavement preservation for ballot.

NCHRP Update: Amir Hanna

Amir Hanna from TRB gave an overview of the NCHRP proposal and project status. He noted that the SCOH approved approximately 43 new projects for 2003. Some of those projects include implementation of the 2002 design guide, models for reflection cracking (on-hold until the 2002 guide is completed), friction guide including noise and environment, top-down cracking in bituminous pavements, and recycled aggregates in unbound layers. The 2004 project statement reviews will be sent to the submitters in December and the projects will then be selected in March 2003. NCHRP is expecting to have roughly $23 million for transportation research in 2004.

The NCHRP 1-37A design guide deliverables were expected at TRB at the end of November. There will be four months to review the deliverables. A brief introduction (~ 20 pages) should be submitted with the software. The deliverable for the NCHRP 1-39 traffic data forecasting is expected soon, as it will be used as input to the 2002 guide.

NAPA Perspective: Dave Newcomb

David Newcomb gave the NAPA perspective and discussed the industry needs for mechanistic pavement design. Some of the items related to the 2002 design guide that concern NAPA include reliability sensitivity, precision of models, user understanding of design software, and better performance estimates from lab studies. Traffic and construction variability are still problems that cannot be designed for. In terms of reliability sensitivity, NAPA would like to know how the design procedure handles the real effects of variability on performance. Other questions include how the models will precisely reflect measurable material properties, as well as better estimates of the endurance limit and stress reduction (need for laboratory studies exists). He also explained that although the design models require complexity, the user needs to know where inputs come from and to avoid cataloging of pavement sections.

The strategic plan and new research areas for NCAT were discussed along with the concurrently occurring Test Track event and Best Paving Practices workshop.

The World of Asphalt trade show and conference will be held on March 17-19, 2003 in Nashville, Tennessee.

ACPA Perspective: Gerry Voigt

Gerry Voigt from ACPA discussed the concrete industry perspective on the 2002 design guide. Some of the main interests include how the new guide compares with the old design procedure and what are the fatigue models for concrete. He also discussed the ACPA priority research issues that include smoothness, early cracking, material compatibility, and zero-clearance paving.

IPRF on the Federal Aviation Administration side is still active.

Some of the important issues for concrete industry are smoothness, profilers, and new concrete mix design process. They would like to come up with one specification for smoothness for all surfaces (not just PCC or AC). Are profilers really giving us an accurate indication of ride? Research will be focused on profiles; however, they will stop short of getting into an index since none of them properly accounted for tining (texturing) and joints on concrete. Iowa is the lead state in coming up with a new concrete mix design process.

Rolling Wheel Deflectometer: Max Grogg

Max Grogg from FHWA-Iowa office gave a presentation on the Rolling Wheel Deflectometer which is a dual-tire dynamic tool that runs at highway speed. The lasers and accelerometers are carried on an insulated aluminum 2 x 8 beam under the rear axle of a tractor trailer. Proof of concept trials were run in Champaign, IL, in July 2002 and he reported that the data for deflections looks promising. Deflections are gathered to the 0.001 inch, making the device an alternative to the Falling Weight Deflectometer (FWD). Need exists to compare network level testing to project level testing.

Demonstration of the 2002 Pavement Design Guide

Overview of the Guide Project, Mike Darter

An overview of the 2002 design guide was then presented by the Contractors that discussed the background, software design/analysis process, implementation issues, and benefits of the guide. The details of the presentation are included in the presentation which is attached.

States can adjust the performance models as needed for local calibration, in order to refine characteristics and variations in the guide to their state.

Some initial comments from the JTF panel on this portion of the meeting included:

  • There is no way to input admixtures (e.g. fly ash) and only regular Type I, II, etc., concrete can be evaluated in guide. Gerry Voigt from ACPA thought it would be important to add that option to the software.
  • Max Grogg suggested that on all the plots for predicted cracking in concrete, there will be a box in the bottom right that gives the actual value (e.g., 68% reliability) that a State pavement design engineer would be interested in knowing.
  • If cracking limits on standard deviation in a State vary from the national norm, the State can manipulate the crack reliability equation for concrete. The JTF noted that this capability should be limited in order to avoid errors prompted by engineers getting lost in the software.
  • The program does not automatically change built-in warping for concrete. The user must go in and manually change it.
  • Traffic and climate data are all from LTPP sites; however, in the future, the climate data could be updated yearly from the NOAA or NCDC data sites.
  • The appendices should include details on the calibration equations used for both flexible and rigid equations.
  • What should the pavement design engineers do for national and State calibration? How can they compare this design process to the previous guide?
  • An appendix should be added to outline the approximate run times for different types of computer systems. Run times should not be different for Level 1, 2, or 3 analyses.

The overview was followed by a software demonstration of the concrete and asphalt design guide procedures.

Demonstration of the Software for PCC

An example of two concrete pavement designs were demonstrated using the software.

Select metric or english at start, but cannot switch back and forth. Main screens are general project information, inputs and results. Color coded:

·Red: stop, input is required to run the program,

·Green: user has supplied the required information or selected default input values,

·Yellow: item has a default value or unnecessary inputs, program will use default value only after the user approves it.

· Help button that does calculations

Traffic default values for the various classes (17) of vehicles and types of roads were drawn from approximately 300 LTPP sites. Traffic type adjustments are per month; therefore, numbers must sum up to 12 (for 1 year). Tire pressure can be changed to reflect increased tire pressures from Supersingle (wide-based radial) tires. Mechanistic models should handle a range of 50 to 200 psi, but Matt Witzcak is recommending looking at only 120 to 140 psi. This may be short-sighted to not calibrate models to higher pressures (i.e., contact areas) and other tire configurations since the tire industry is ever-evolving and producing new tire types.

Hourly climatic database draws from 800 locations around the US. Also accounts for thermal gradients in the pavement, but only at 3 depths (top, middle, bottom) within the pavement layer.

The software requires user to define the pavement layers and structure proposed. In design features, the effects of dense-treated base versus coarse-treated base with respect to erodibility can be investigated.

Reliability is included in the pavement design models. One issue to be explained was how they are looking at fairly comparing reliability for different pavement distresses (for different pavement types). They listed a table with ranges of reliability for different distress types.

NOVEMBER 13

AC Models, Chuck Schwartz

A presentation on the calibration of the asphalt pavement models was given along with a demonstration of a flexible pavement design example. The details of the presentation are included in attached file. Some comments and highlights on the flexible pavement design include:

  • Models designed to account for interaction of distresses and effect on calibration (e.g., pavement may have both top-down and bottom-up cracks simultaneously and how they influence eachother).
  • NCHRP 9-30 reports have some explanation of calibration factors and models for rutting and cracking that are used in the Design Guide.
  • Some of the damage models for flexible pavement distress (e.g., top-down cracking) are not yet completed.
  • Cracking data (e.g., cumulative crack length in 500-ft long section) is generated from LTPP field data, but only using test at one temperature.
  • Traffic wander data from LTPP. Which sites?
  • Not enough attention is paid to material characteristics on the flexible pavement design. Also, the unbound layer values k1, k2, and k3 must be computer and input by the user.
  • Temperature divisions within the asphalt concrete layer are broken into various sublayers in the analysis, but the user does not see how many sublayers are used. Temperature is coming from weather stations. Example: in a 10-inch AC layer, the pavement temperatures are measured at 3 depths for the routine. In the case of thermal and top-down cracking, the model concentrates on temperature in the top one-half inch of the pavement layer.
  • The analysis type for environmental effects is the Enhanced Integrated Climatic Model (ICM). For example, cold weather analysis must be done using the ICM.
  • Models not yet calibrated for all of the flexible pavement distresses (e.g., top-down cracking).

Closed Session

Items for Discussion:

  • Membership increase
  • Keeping up-to-date on provisional standards for tests, etc.
  • Letter from Gary Hoffman of Pennsylvania DOT
  • Variation in Resilient Modulus
  • Joint review of draft 2002 design guide
  • Upcoming JTF on Pavements meeting
Membership Increase

Item deals with the idea of inviting four (4) members, one from each region of the US, from the Subcommittee on Materials (SOM) to participate in the JTF on Pavements meetings.

Mike Ryan from the SOM is looking for suggestions of names before February and they want to make sure and get one member from each region.

Members of JTF group should email names to Gary Sharpe (

503-564-3280) within the next month (by December 1, 2002). Gary will then send the names to Ken Kobetsky.

Panel also discussed coordinating with other subcommittees (FAA, Planning) to invite member(s) from their respective groups to attend the JTF on Pavements meetings and to find out if the current contact from their committees is still interested in serving on our committee. Task Force chairman will first phone and then send a letter to find out.

The possibility of extending an invitation to the US Corps of Engineers to attend, but not as a member, was also discussed. It was decided that David Pittman would be a contact but that the JTF would wait until after the 2002 design guide is completed to make the invitation.

Recent travel restrictions are making it difficult for State members to attend the JTF on Pavements meetings. Therefore, the JTF has decided not to ask for replacements from the States for members who have missed more than two (2) meetings.

Provisional Standards for Tests

Item deals with the keeping up with provisional standards for tests, etc. Some contacts were identified for:

P 46 Andy Gisi from Kansas DOT

TP 7, 8, & 9 Mix ETG task force led by Richard Kim from NC State University

NCHRP 9-29Dynamic Modulus of Asphalt, Rick Harvey & FHWA on panel

Gary Sharpe noted that once the provisional standards are balloted and approved, Steve K. will be invited to brief the JTF on Pavements once the draft is final. Gerry Voigt (ACPA) requested comments and Ken Fults and Danny Dawood will draft a response to Gerry Voigt.

Letter from Gary Hoffman of Pennsylvania DOT

Item deals with a letter sent to Gary Sharpe from Gary Hoffman, Chief Highway Engineer at Pennsylvania DOT. The letter concerns whether or not the JTF can promote the use of the zero blanking band (ZBB) to get all of the States to get together on achieving consistent paving. Kansas was identified as having done a great amount of research on the ZBB. Some states have already moved from ZBB to IRI including Texas, Pennsylvania, Maryland, and Wyoming to name a few.

The suggestion was made to go around ZBB and start directly promoting IRI. By using the expertise on the Task Force, group could come up with a “white paper” that explains the reasons to go towards index-based profile. Specifically, historical examples of States that have already moved would be helpful. Tom Hearne, Linda Pearce, Andy Gisi, and Ken Fults will work on the “white paper”.

Variation in Resilient Modulus

Dan Dawood mentioned that the 2002 guide should have endorsement from some Agency. Gary Sharpe mentioned that once the 2002 Guide is approved by the JTF on Pavements, that will constitute JTF on Pavements endorsement.

Ken Fults will work with Andy Gisi in deciding which one (128-A) that Matt Witzcak is using.

Dan Dawood and Amir Hanna will verify what provisions are in the Guide.

Joint Review of Draft Guide

Joint review of the draft 2002 pavement design guide will be done along with the NCHRP panel review. Amir Hanna noted that the preliminary draft will be made available to the JTF on Pavements for review. The JTF on Pavements will have 2 months for review. Amir would like comments to be sent from members to him and he agreed to send the software to the JTP on Pavements members in order for them to become familiar with the program.

Upcoming JTF on Pavements Meeting

The next meeting will be held in Little Rock, Arkansas, in mid-May 2003. The Subcommittee on Design is meeting June 10-13, 2003, in Boston, Mass.