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Environmental Conditions and Binder Aging Characteristics in the Intermountain Region of the United States
AuthorCortez, Edward Madariaga
AdvisorSebaaly, Peter E.
Civil and Environmental Engineering
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Thermal cracking is a major form of distress in much of the northern United States. Moreover, field performance data indicate that HMA mixtures in the intermountain region of the U.S. experience severe thermal cracking distresses that are not well covered by current technology. The objective of this research is to develop a binder/mix evaluation and testing system that can effectively simulate the long term properties of HMA mixtures in the intermountain region and to assess the impact of such properties on the resistance of HMA mixtures to thermal cracking.Particularly, the binder aging kinetics when there is free access to atmospheric oxygen was evaluated. One millimeter film of various asphalt binder types were subjected to long-term oven aging at various temperatures and time periods in ovens with full access to atmospheric oxygen. Mass change was monitored throughout the test. Various properties of the aged binders will be or are already measured: carbonyl growth to determine binder reaction rates and activation energies, rheologic properties, strength properties, and thermal expansion coefficient. Ultimately, the various properties measured will prove valuable during the development of a mixture aging model for the intermountain region.Additionally, environment and pavement temperature data from fourteen Long Term Pavement Performance sections and four WesTrack sections were available and analyzed. All sections are located within the intermountain region. This region represents a unique environment that impacts HMA mixtures in a manner that is different than the other regions of the United States. It was imperative that these unique features were closely investigated. A database containing pavement temperature rates as well as other relevant properties pertaining to thermal cracking is now available. Recommendations have been presented to better simulate environmental conditions present in the intermountain region.The two evaluations will ultimately be used in a mixture aging model. The impact of aggregate and mixture properties on the aging of the binder in the mix will be evaluated in another phase and will also be incorporated into the same mixture aging model.