Investigation of Short-Term Laboratory Aging of Neat and Modified Asphalt Binders (2011) / Chapter Skim
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The project started with a review of existing binder aging procedures to identify viable candidate methods for possible improvement. Two viable methods were identified: the Stirred Air Flow Test (SAFT)
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Identify Viable Candidate Methods Volatile Collection System Study SAFT Optimization Study Verification Study Stirred Air Flow Test Modified German Rotating Flask Recommendations Figure 2-1. Flowchart for NCHRP Project 9-36.
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As well, components -- primarily oils used in the preparation of modified asphalt binders -- also may vaporize and escape into the atmosphere. The RTFOT provides a means of measuring mass change, which includes the loss of mass resulting from volatilization as well as mass gain that can result from oxidation.
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The ideal aging procedure should • Simulate both long-term and short-term aging; • Be performed at two temperatures, one representing conditions at the hot mix plant and the other representing, as close as possible, service temperatures; • Include a procedure for capturing and measuring volatile loss during short-term aging; • Provide sufficient material for characterizing the physical properties of the binder after short- and long-term aging; • Complete long-term aging within 46 hours; • Be applicable to both neat and modified asphalt binders; • Accommodate binder- and modifier-specific aging kinetics in the long-term aging; • Be safe and technician-friendly; and 9
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air blowing were identified in the review of the literature and research in progress. Consideration of the fundamental aging process in these three approaches and the requirements of the ideal aging procedure for specification testing were used to select approaches and candidate procedures for further consideration.
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During the heat-up phase, the temperature of the binder is increased from approximately 100°C to the testing temperature of 163°C 11 Test Conditions Investigated Modified German Rotating Flask Morton versus smooth flask Rotational speed Mixing enhancers Scrapers Stirred Air Flow Test Impeller type Position of air supply Rotational speed of impeller Table 2-2. Summary of conditions investigated during the selection study.
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In the oven-aged mixtures experiment, hot mix asphalt was prepared with the binders from the RTFOT verification experiment and aged in accordance with the performance testing protocol in AASHTO R30. Dynamic modulus master curve tests were performed on the mixture samples.
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. 2.7 Materials 2.7.1 Binders NCHRP Project 9-36 used 13 different asphalt binders: seven neat binders and six modified binders.
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The Citgoflex and Novophalt binders also were used in the selection study. All of the MRL binders and all of the modified binders were used in the verification study.
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