Development of Long-Term Aging Protocol for Implementation of the Illinois Flexibility Index Test (I-FIT)
Al-Qadi, Imad L.; Ozer, Hasan; Zhu, Zehui; Singhvi, Punit; Mohamed Ali, Uthman; Sawalha, Mohammed; Espinoza Luque, Arturo Francisco; Garcia Mainieri, Javier Jesus; Zehr, Thomas G.
- Development of Long-Term Aging Protocol for Implementation of the Illinois Flexibility Index Test (I-FIT)
- Al-Qadi, Imad L.
- Ozer, Hasan
- Zhu, Zehui
- Singhvi, Punit
- Mohamed Ali, Uthman
- Sawalha, Mohammed
- Espinoza Luque, Arturo Francisco
- Garcia Mainieri, Javier Jesus
- Zehr, Thomas G.
- Issue Date
- Asphalt Mixture
- Illinois Flexibility Index Test (I-FIT)
- Long-term Aging
- Flexibility Index
- Aging Rate
- The objective of this study was to evaluate long-term aging effects on asphalt mixtures using the Illinois Flexibility Index Test (I-FIT) and to develop a corresponding long-term aging protocol. The study recommended the use of the forced-draft oven as the aging equipment because of its availability, feasibility, practicability, capacity, and acceptable variability. A fully prepared semi-circular I-FIT specimen was chosen as the state of material during aging because it is practical, has limited operational variability, and its integrity is maintained during aging. The aging of compacted specimens for three days at 203°F (95°C) was found to be similar to aging for five days at 185°F (85°C) according to AASHTO R30, which is believed to be able to simulate up to 10 years of field aging. Hence, the 3D/95C aging method was chosen as the key component of the long-term aging protocol. Based on statistical analysis and oven-aging specimens immersed in argon, it was shown that the trends of aging after 1D/95C were similar to that observed after 3D/95C and 5D/85C. Hence, 1D/95C may be used as an indicator of 3D/95C aging for quality control purposes. Aging protocols were developed for laboratory-produced laboratory-compacted (LPLC) and plant-produced laboratory-compacted (PPLC) specimens. For LPLC, I-FIT on unaged and 3D/95C aged specimens should be conducted in all cases. A specific mix must have a mean flexibly index (FI) of unaged and 3D/95C aged specimens greater than 8.0 and 5.0, respectively, to be accepted. For PPLC, I-FIT procedure should be conducted on both unaged and 3D/95C aged specimens in all cases, while 1D/95C may be used by contractors to screen problematic mixes. Flexibility index higher than 8.0 and 4.0 for unaged and 3D/95C aged specimens, respectively, must be satisfied.
- Illinois Center for Transportation/Illinois Department of Transportation
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- No restrictions. This document is available through the National Technical Information Service, Springfield, VA 22161.
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