Browsing by Author "Cash, Kristen"
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Item Development of Superpave 5 Asphalt Mix Designs for Minnesota Pavements(Minnesota Department of Transportation, 2022-06) Yan, Tianhao; Marasteanu, Mihai; Le, Jia-Liang; Turos, Mugurel; Cash, KristenHigh field density is desired for improving the durability of asphalt pavements. This research aims to develop Superpave 5 mixtures (more compactable than traditional Superpave mixtures) by using locally available materials to improve the field density in Minnesota. First, previous projects in Minnesota were investigated. The mean and standard deviation of field density in Minnesota were about 93.5% Gmm and 1.5% Gmm, respectively. Significant correlations were identified between field density and mix design indices, i.e., Ndesign, NMAS, and fine aggregate angularity (FAA). Four traditional Superpave mixtures were then selected and modified to Superpave 5 mixtures by adjusting their aggregate gradations while maintaining the asphalt binder content. Laboratory performance tests were performed to check the mechanical properties of the modified mixtures. The results showed it was feasible to design Superpave 5 mixtures (more compactable mixtures) by adjusting aggregate gradations, and the improved compactability of the mixtures did not adversely affect the performance of the mixtures for rutting, stiffness, and cracking resistance. Therefore, Superpave 5 mixtures can increase field density as well as other performances of asphalt pavements if implemented.Item Investigation of Rutting Resistance of Superpave 5 Asphalt Mixtures(2021-12) Cash, KristenThe Superpave mix design method has been used for more than two decades to design asphalt mixtures used in the construction of asphalt pavements. While permanent deformation (rutting) distresses have been virtually eliminated, the durability distresses, e.g., cracking, moisture damage, and raveling, have become the predominant distresses that control the service life of asphalt pavements. A new method, the Superpave 5 design method, was recently developed to reduce this issue and to improve the durability of asphalt pavements. The new method increases the compactibility of asphalt mixtures, which results in increased as-constructed densities of the asphalt mixtures placed in the field. While there is evidence that this new mix design reduces durability issues, there is concern that the increased compactability will negatively affect the rutting resistance of the mixtures. To investigate the validity of this concern, four traditional Superpave 4 (SP4) asphalt mixtures were modified to match the requirements of the new Superpave 5 (SP5) mix design by changing their aggregate gradation to make them more compactable. The compacted specimens were subjected to performance tests, such as SCB (semi-circular bending) test, |E*| (diametral dynamic modulus) test, and flow number test. The performance test results showed that the SP5 mixtures have better rutting and cracking resistance, compared to the original SP4 mixtures, and the concern associated with more compactable mixtures is not valid.