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3CHAPTER 1 INTRODUCTION AND RESEARCH APPROACH 1.1 PROBLEM AND PURPOSE NCHRP Project 9-19, Superpave Support and Perfor- mance Models Management, recommended three candidate simple performance tests to complement the Superpave vol- umetric mixture design method. These are flow time, flow number, and dynamic modulus. The recommended tests are conducted in uniaxial or triaxial compression on cylindrical specimens that are sawed and cored from over-height gyra- tory compacted samples. Data from all three candidates were shown to correlate well with observed rutting in field pave- ments. The dynamic modulus was also shown to have poten- tial as a simple performance test for fatigue cracking. In NCHRP Project 1-37A, Development of the 2002 Guide for the Design of New and Rehabilitated Pavement Structures: Phase II, the dynamic modulus was recommended as the pri- mary material characterization test for asphalt concrete lay- ers. The use of this test for both mixture evaluation and struc- tural design offers a potential link between mixture design and structural analysis that was one of the goals of the origi- nal Superpave mixture analysis system. Although additional work is being done in NCHRP Project 9-19 to further evaluate the candidate tests and develop accep- tance limits, the test methods were defined to the point that equipment development could be conducted in parallel with the remaining Project 9-19 and Project 1-37A activities. The objective of Project 9-29 is to stimulate the development of commercial equipment that can be used for two purposes: 1. For simple performance testing to complement Super- pave volumetric mixture design, and 2. For the asphalt concrete material characterization required by future pavement structural design methods. This project is the first in a series of equipment development efforts that will lead to a national procurement for state high- way agencies and ultimately to the widespread adoption and use of the equipment by the hot-mix asphalt (HMA) industry. 1.2 SCOPE AND RESEARCH APPROACH The project consisted of eight tasks assembled into two phases. The first phase comprised the following five tasks aimed at the development of detailed equipment purchase specifications and a plan for evaluating the first-article devices that were purchased during Phase II: 1. Review the draft test protocols prepared by the Project 9-19 research team. This review included a 1-day work- shop attended by the project panel, key members of the research team, and invited materials testing experts to discuss the requirements for the simple performance test devices. 2. Develop draft equipment specifications and cost esti- mates for the three candidate tests. Individual draft equipment specifications were developed for the three candidate tests. These were then combined to specify a device capable of performing all three tests. 3. Conduct a workshop with the project panel and poten- tial manufacturers to review the draft specifications and cost estimates. This workshop was attended by 10 man- ufacturers who provided several comments on the draft equipment specifications that were incorporated into the first-article equipment specifications. 4. Develop a work plan for evaluation of the first-article equipment. The work plan included the methods for verification that the first-article equipment met the spec- ifications as well as a laboratory experiment to evaluate the performance of the first-article equipment and the repeatability/reproducibility of data obtained with it. 5. Prepare and submit an interim report documenting the work completed in the first phase of the project. The second phase of the project comprised three tasks asso- ciated with the procurement and evaluation of two first-article devices and the revision of the equipment specifications and draft test protocols based on the evaluation. These tasks were as follows: 6. Solicit manufacturers, evaluate proposals, and procure two first-article devices from different manufacturers. First-article devices were procured from Interlaken Technology Corporation and Shedworks, Incorporated. 7. Perform the first-article evaluation in accordance with the plan developed in Task 4. Analyze the data and develop
4recommendations concerning the equipment evaluated and revise the equipment specifications, cost estimates, and Project 9-19 Draft Test Protocols as needed. 8. Prepare and submit a final report documenting the work performed during Phase II. The report includes stand- alone appendices presenting the final equipment speci- fications, and recommended changes to the Project 9-19 Draft Test Protocols. Details of the Phase I work were documented in the Interim Report submitted on October 10, 2001. This report documents the work completed during Phase II of the project.
