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AASHTO T 378:2017 Standard Method of Test for Determining the| Dynamic Modulus and FIow Number for Asphalt Mixtures Using the Asphalt Mixture Performance Tester (AMPT). 4. SUMMARY OF METHOD 4.1. This test method describes procedures fur measuring the dynamic modulus and flow number for asphalt mixtures. 4.2. In the dynamic modulus procedure, a specimen at a specific test temperature is subjected to a controlled sinusoidal (haversine) compressive stress of various frequencies. The test may be conducted with or without confining pressure. The applied stresses and resulting axial strains are measured as a function of time and used to calculate the dynamic modulus and phase angle. 4.3. In the flow number procedure, a specimen at a specific test temperature is subjected to a repeated haversine axial compressive load pulse of 0.1 s every 1.0 s. The test may be conducted with or without confining pressure. The resulting permanent axial strains arc measured as a function of the load cycles and numerically differentiated to calculate the flow number. The flow number is defined as the number of load cycles corresponding to the minimum rate of change of permanent axial strain. 5. SIGNIFICANCE AND USE 5.1. The dynamic modulus is a performance-related property that can be used for mixture evaluation and for characterizing the stiffness of asphalt mixtures for mechanistic-empirical pavement design. 5.2. The flow number is a property related to the resistance of asphalt mixtures to permanent deformation. It can be used to evaluate and design asphalt mixtures with specific resistance to permanent deformation. 6. APPARATUS 6.1. Specimen Fabrication Equipment—For fabricating dynamic modulus test specimens as described in R 83. 6.2. Dynamic Modulus Test System—Meeting the requirements of the equipment specification for the Simple Performance Test (SPT) System, Version 3.0, except for the following provisions: In the referenced equipment specification, Sections 10.7 and 11.3 shall require a temperature sensor range of 0 to 75°C (32 to 167°F) and Section 11 .1 shall require a temperature control range from 4 to 70°C (3910 158°F). 6.3. conditioning Chamber— -An environmental chamber for conditioning the test specimens to the desired testing temperature. The environmental chamber shall be capable of controlling the temperature of the specimen over a temperature range from 4 to 70°C to an accuracy of ±0.5°C. The chamber shall be large enough to accommodate the number of specimens to be tested plus a “dummy” specimen with a temperature sensor mounted in the center...

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