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Effect of Antioxidant Additives and Recycling Agents on Performance of Asphalt Binders and Mixtures – Phase II
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2024-11-01
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[PDF-2.50 MB]
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Edition:Final Report
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Abstract:The use of reclaimed asphalt pavement (RAP) in combination with recycling agents (RAs) (i.e., rejuvenators or softening agents) has gained significant attention from the pavement industry as a sustainable pavement solution, reducing the carbon footprint of manufactured products through the conservation of energy and reduction on the use of raw materials. Current research has found that RAs can improve RAP recycled asphalt mixture’s cracking resistance, while being capable of maintaining their rutting resistance. However, there are some concerns about the effect of RAs on the moisture damage resistance and the long-term performance (aging) of these additives. The current need is to maximize the use of RAP in asphalt mixtures by adopting sustainable sources of RAs, such as Triglycerides and Fatty Acids (TF) based RAs which are mostly derived from vegetable oils. However, Phase I of this project found that TF-based RAs are more prone to oxidative aging, which can hamper the long-term performance of asphalt binders and mixtures. In the current project (Phase II), we focused on adopting the simultaneous utilization of RA and antioxidants to prevent the oxidative aging of RA-modified binders and mixtures. To this end, different binder blends and high-RAP mixtures were developed using five different antioxidants alongside the high-RAP binder modified with one source of TF-based RA. At the binder level, rheological performance tests were conducted focusing on high-temperature rutting, and mid and low-temperature cracking assessments at short and long-term aging conditions. Additionally, at the mixture level, two antioxidants were selected to develop high-RAP asphalt mixtures modified with TF-based RA, and mechanical performance testing focusing on mid-temperature cracking, rutting, and moisture damage susceptibility were performed. At the binder level, the results revealed that the addition of TF-based RA enhanced the binder’s cracking resistance but increased the rutting susceptibility. Antioxidants did not affect the rutting and cracking parameters; however, their effect on resisting long-term aging was antioxidant-type specific. At the mixture level, the selected dosage of TF-based RA could not enhance the mixture cracking resistance significantly. Also, the effects of TF-based binders were not observed at long term aging conditions. Similar to the binder level results, the use of antioxidants to retards oxidative aging was type-specific, and one antioxidant, Zinc diethyldithiocarbamate (ZnDEC), provided such superior aging-resistant function.
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