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Assessing the Effects of RAP, RAS, and Warm- Mix Technologies on Fatigue Performance of Asphalt Mixtures and Pavements Using Viscoelastic Continuum Damage Approach

Wei Cao, Louay N. Mohammad, Mostafa Elseifi


The objective of this study was to evaluate the effects of incorporating recycled materials, i.e., reclaimed asphalt pavement (RAP) and recycled asphalt shingles (RAS), and the use of warm-mix technologies on fatigue performance of asphalt mixtures and pavement structures using the viscoelastic continuum damage (VECD) approach. For this purpose, ten mixtures from the full-scale test lanes constructed at the Federal Highway Administration (FHWA) Accelerated Loading Facility (ALF) were acquired and characterized in the laboratory. The dynamic modulus test and direct tension cyclic fatigue test were employed to assess the linear viscoelastic property and fatigue characteristics, respectively. Within the VECD framework, two parameters, namely material fatigue sensitivity (MFS) and structure fatigue sensitivity (SFS) were developed to represent the fatigue resistance of asphalt mixtures and their performance in pavement structures, respectively. Both parameters can be easily obtained via the strain-based fatigue simulation using the experimental data without extra requirements on the specimen failure location and the number of cycles to failure in the cyclic fatigue test. The validity of MFS was verified by the critical strain energy release rate obtained from semi-circular bend (SCB) testing at intermediate temperature. Based on the obtained dynamic modulus and MFS data, an increase in the content of recycled materials was able to enhance the stiffness of hot-mix asphalt (HMA) mixtures while compromising the fatigue resistance. Implementation of warm-mix technologies benefited materials’ fatigue performance but the improvement was not substantial. Use of soft binder yielded pronounced fatigue benefits for HMA mixtures with high RAP content. The proposed SFS parameter resulted in the same performance ranking of the ALF lanes as the measured fatigue lives. Moreover, quantitatively a power-law function was found to adequately correlate SFS with the field measurements.

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