Simple Performance Tests: Summary of Recommended Methods and Database (2006)

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1CHAPTER 1 INTRODUCTION A key objective of NCHRP Project 9-19, “Superpave Sup- port and Performance Models Management,” was to develop simple performance tests for permanent deformation and fatigue cracking for incorporation in the Superpave volu- metric mix design method. NCHRP Report 465: Simple Performance Test for Superpave Mix Design summarized analytical and experimental work conducted originally at the University of Maryland from 1995 to 2000 and then at Arizona State University (ASU) to (1) survey the range of potential simple performance test methods and (2) select the most promising methods for a field validation program. Based on the results of the testing program in Project 9-19, three tests were recommended for further field validation as promising simple performance tests for permanent deforma- tion: (1) dynamic modulus, E*, determined by the triaxial dynamic modulus test; (2) the flow number, Fn, determined from the repeated load test; and (3) the flow time, Ft, deter- mined from the static creep test. Between 2001 and 2004, ASU and its subcontractors car- ried out an extensive series of experiments to validate the dynamic modulus, flow time, and flow number tests with materials and data from accelerated pavement tests and full- scale field tests. In 2004, based on the results of these exper- iments, the dynamic modulus test was recommended as the primary simple performance test for rutting. The flow num- ber test was recommended as a complementary procedure for evaluating the resistance of a hot mix asphalt (HMA) mix design to tertiary flow; the flow time test was shown to be a simple, practical surrogate for the flow number test. In subsequent work, ASU prepared a specification for rutting, in the form of a Microsoft Excel spreadsheet, that determines a critical minimum E* value for HMA (based on project-specific information on climate, traffic, pavement structure, and layer depth); work to develop a simple speci- fication for fatigue cracking will be completed in 2005. Both specifications are based on a series of pavement design examples pre-solved with the mechanistic-empirical pave- ment design guide software developed in NCHRP Project 1-37A, “Development of the 2002 Guide for the Design of New and Rehabilitated Pavement Structures: Phase II.” This report summarizes the theory behind the three recommended simple performance tests, briefly describes the test methods, and presents appendixes on the included CD-ROM (CRP-CD-46) that contain (1) all the test data, mixture data, master curves, and master curve parameters obtained from the E* testing and analysis; and (2) all the test and mixture data obtained from the Fn and Ft tests, including εp (permanent strain at flow), εr (recoverable strain at flow), εp/εr (from the Fn test), and compliance (from the Ft test). Both plant mixes and laboratory-blended short-term oven- aged mixes were tested under the project. Mixtures from MnRoad, NCAT Test Track, Indiana, Nevada I-80, Wes- Track, FHWA-ALF, and Arizona DOT (ADOT) I-10 sites constituted the complete test matrix. ASU also conducted dynamic modulus, flow number, and flow time testing for these other research projects: 1. ADOT AC Mixture Stiffness Characterization Data- base (Project #3 of the ASU-ADOT Research Program: “Development of Performance Related Specifications for Asphalt Pavements in the State of Arizona”) and associated tasks (US-60 plant mixes and Two Guns lab blend and plant-mixed conventional and rubber mixes); 2. Asphalt Rubber Demonstration Project (ADOT I-40 site); 3. Performance Evaluation of Arizona Asphalt Rubber Mixtures Using Advanced Dynamic Material Charac- terization Tests (ADOT I-17 site); 4. Alberta Asphalt Rubber Project (2002 AR Mix #1 and 2003 AR Mix #2); 5. NCHRP 9-23 Project (Environmental Effects in Pavement Mix and Structural Design Systems); 6. Development of an E* Master Curve Database for Lime Modified Asphaltic Mixtures; 7. ADOT AC Mixture Permanent Deformation Database (Project #5 of the ASU-ADOT Research Program: “Development of Performance Related Specifications for Asphalt Pavements in the State of Arizona”); and 8. ADOT AC Mixture Simple Performance Tests (Project #7 of the ASU-ADOT Research Program: “Develop- ment of Performance Related Specifications for Asphalt Pavements in the State of Arizona”). For completeness all E*, Fn, and Ft results obtained through the testing and analysis of these other projects are also included in the appendixes contained on CRP-CD-46.