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12 Figure 2-4. Prototype SAFT (left) and commercial SAFT (right). while nitrogen flows through the SAFT vessel. Since the start- draft oven in accordance with the performance testing pro- ing temperature (temperature of the binder after charging the tocol contained in AASHTO R30. Initially, the verification SAFT vessel) cannot be accurately controlled, it is critical that study only included the SAFT, but it was expanded at the the heat-up phase not contribute significantly to the degree of request of the NCHRP project panel to include the MGRF. aging that occurs in the test. The second component of the The verification study consisted of two parts: (1) the RTFOT SAFT optimization study was an experiment to determine the verification experiment and (2) the oven-aged mixtures exper- effects of impeller speed, airflow rate, and test duration on iment. The RTFOT verification experiment, which included the degree of aging measured by the high pavement tempera- dynamic shear rheometer (DSR) and bending beam rheome- ture rheology of the binder. From this component of the SAFT ter (BBR) measurements, was designed to provide master optimization study, operating parameters for the commercial curves for the binders in the tank condition and after SAFT, SAFT were selected. These operating parameters were used in MGRF, and RTFOT conditioning. These binder master curves the verification study described in the next section. Findings served two purposes: (1) to allow a comparison of the rheolog- from the SAFT optimization study are presented in Chapter 3. ical properties of material conditioned in the SAFT, MGRF, The SAFT optimization study is documented in Appendix D and RTFOT and (2) to allow a comparison of the master curves (available on the TRB website). measured for the binders and the master curves back-calculated from mixture properties. In the oven-aged mixtures experi- ment, hot mix asphalt was prepared with the binders from the 2.6 Verification Study RTFOT verification experiment and aged in accordance with The objective of the verification study was to (1) verify that the performance testing protocol in AASHTO R30. Dynamic the commercial version of the SAFT and the MGRF reproduce modulus master curve tests were performed on the mixture the degree of aging obtained in the RTFOT for a wide range of samples. From the mixture modulus master curves, the binder neat binders and (2) compare the aging from the SAFT, MGRF, stiffness was estimated using the Hirsch Model (6) and com- and RTFOT with that from mixture samples aged in a forced pared to the measured stiffnesses obtained from the SAFT,