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Mid-America Transportation Center

Research on High-RAP Asphalt Mixtures with Rejuvenators and WMA Additives

Final Report
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Researchers

  • Principal Investigator: Yong Rak Kim (ykim3@unl.edu (402)472-1727)
  • Project Status
    Complete
    Sponsors & Partners
  • Nebraska Department of Roads
  • Abstract
    This study is to evaluate the mechanical and chemical properties of the asphalt concrete (AC) mixture, fine aggregate matrix (FAM), and binder modified by three different rejuvenators and warm mix asphalt (WMA) additive. In this regard, for testing of AC mixtures, the dynamic modulus, dynamic creep, and semicircular bending (SCB) fracture tests were conducted. For testing of FAM mixtures, three types of strain-controlled torsional oscillatory shear tests (i.e., strain sweep, frequency sweep, and time sweep) and the static creep-recovery tests were employed for comparative purposes. For binders, the Fourier transform infrared (FTIR) spectroscopy, saturates-aromatics-resins-asphaltenes (SARA) analysis, dynamic shear rheometer (DSR), and atomic force microscopy (AFM) were used to characterize the physicochemical and mechanical aspects of the asphalt binders. Based on test and analysis results, the rejuvenators can soften the materials, increase the rutting potential and may mitigate moisture damage resistance, while improving cracking and fatigue resistance of the asphaltic mixtures. A comparison between AC mixtures and corresponding FAM mixtures revealed the interrelationships between the two length scales. From the binder tests, it appears that the rejuvenators decrease either carbonyl or sulfoxide or both indices. Addition of rejuvenators to the mixture of recycled asphalt binder and virgin binder led to a decrease in the amount of asphaltenes. Furthermore, rejuvenators improved colloidal instability index (CII), which implies that the aged binder has become more stable due to rejuvenation. The AFM phase images of binders indicated that the softening effect of rejuvenators corresponds to the mechanical test results from DSR.
    Project Amount
    $ 161,451.02