Modulus of recycled hot mix asphalt: Micromechanical modeling and experimental approaches

To improve the availability of reclaimed asphalt pavement (RAP) in recycled hot mix asphalt (HMA), this study is focused on the mechanical performance of recycled HMA, which is beneficial for environmental conservation and consistent with the concept of sustainability. To alleviate the heterogeneity of the material composition of recycled HMA and enhance the usability and applicability of research means, micromechanical modeling is used to examine the modulus of recycled HMA, which is a critical parameter for asphalt pavement analysis. In this investigation, a four-layer built-in micromechanical model was constructed and derived to characterize recycled HMA. The micromechanical model indicated that the modulus of recycled asphalt was the main factor influencing the modulus of recycled HMA. Thus, the following study took the modulus of recycled asphalt as the main study subject. The frequency sweep test and three-point flexure beam test for recycled asphalt were designed and conducted to clarify the change trend of influence factors and further verify the reasonability and feasibility of the micromechanical model. Considering the diffusion behavior of the rejuvenator, the change trends of the factors are explored. The curing time apparently influences the modulus of recycled asphalt, followed by the curing temperature and the rejuvenator proportion. Finally, analytical results from micromechanical model matched well with the experimental results. The results of this study may be valuable for predicting the dynamic moduli of recycled HMA.