NCHRP 20-7

Proposed Research Needs Statement

AASHTO - Subcommittee on Materials, Technical Section 2c (Asphalt-Aggregate Mixtures)

Committee Chair - Thomas E. Baker, WSDOT

Committee Vice-Chair – Allen H. Myers, KYTC

October 1, 2013

TITLE

Hamburg Wheel-Track Test Equipment Requirements and Improvements to AASHTO T 324

BACKGROUND / NEEDS STATEMENT

Technical Section (TS) 2c established a 12-member task force to review and improve AASHTO T 324-11, Standard Method of Test for Hamburg Wheel-Track Testing of Compacted Hot Mix Asphalt (HMA). The task force review identified many areas of improvement and provided recommendations to the TS in the form of a revised standard for ballot and possible publication. The task force also identified several issues within the standard that could not be resolved due to unknown impacts on the test results or unknown impacts to state-specific acceptance criteria resulting from the changes.

One issue identified is the presence of detailed equipment requirements that may limit the use of Hamburg test equipment manufactured by other companies. T 324 details specific equipment requirements that appear to be written around the original Hamburg wheel-track equipment available in the U.S. from Precision Machine & Welding (PMW). Since development of the standard, PMW was purchased by Troxler, and additional manufacturers have entered the market. There are four companies currently marketing Hamburg test equipment in the U.S. with additional manufacturers available internationally. The U.S. manufacturers include:

1.  Troxler - PMW

2.  Cooper Technology - Cox & Sons

3.  InstroTek Inc - IPC Global

4.  Pavement Technology Inc. (PTI)

Prior to Troxler’s purchase of PMW, PMW was unable to meet the state agency and industry demand for Hamburg test equipment resulting in state agency equipment purchases from other companies. Agencies that purchased from other companies believe the current T 324 standard is overly prescriptive and restrictive and would like the method generalized to allow use of other company’s equipment. Agencies with a long history of PMW equipment usage are hesitant to relax the equipment requirements without understanding the impacts to test results, existing equipment, historical test data, and acceptance criteria.

This proposal addresses the issues identified above that could not be resolved by the TS 2c task force and are limiting the availability of equipment to conduct Hamburg testing. As a result of this work, T 324 revisions will be suggested to discourage requirements that artificially limit manufacturer competition within the marketplace.

RESEARCH OBJECTIVE

Document available equipment for Hamburg testing, and provide details on requirements needed to ensure proper testing and accurate results. Provide recommendations and a written research framework for evaluation of critical equipment requirements and their impacts on test results. (Note: This framework and associated recommendations will be used as the basis for a future NCHRP project advertised to conduct the research.)

WORK TASKS

Within the context of AASHTO T 324 Hamburg testing, tasks anticipated in this project include the following:

·  Document the available test equipment capabilities, equipment similarities and differences, and equipment specifications.

·  Provide details on equipment capability to accurately measure, control, and maintain test conditions (e.g., wheel load throughout the load cycle, chamber and test specimen temperature, rut depth at intervals along the loaded wheel path, etc.).

·  Provide details to support a specific capability, equipment component, or design needed to ensure proper testing and accurate results.

·  Provide recommendations on specific AASHTO T 324 equipment requirements that may need to be generalized.

·  Provide recommendations on specific equipment requirements that may need to be added to AASHTO T 324 or strengthened.

·  Provide recommendations and a written research framework for future evaluation of critical equipment capabilities, details, and requirements; repeatability; and their impact on test results.

URGENCY

Some agencies have already purchased equipment to conduct Hamburg testing that does not satisfy the current equipment requirements. Additional equipment innovations and improvements are available in the market that may provide more accurate and repeatable test results if incorporated into an updated test standard. It is critical to determine specific equipment details to preserve within the standard versus equipment details that can be generalized or eliminated to improve the standard, ensure reliable testing, and preserve the value of the historical data already collected.

FUNDING REQUESTED AND TIME REQUIRED

It is estimated that this research will take 12-14 months to complete (including reporting, review, and approval by the NCHRP panel) and will require $100,000.00.

CONTACT PERSON(S)

Matthew Corrigan, P.E. Timothy Ramirez, P.E.

Federal Highway Administration Pennsylvania Department of Transportation

1200 New Jersey Ave SE 81 Lab Lane

Room E73-465 Harrisburg, PA 17110

Washington, DC 20590 Phone: 717.783.6602

Phone: 202.366.1549 Email:

Email: