Blending and diffusion characteristics of virgin and aged asphalt based on improved bending beam rheometer (BBR) test and finite element method

The blending effect of virgin and aged asphalt has a significant impact on the performance of recycled asphalt. The objective of this study was to evaluate the influence of blending and diffusion characteristics of virgin and aged asphalt based on the BBR macroscopic test, FTIR microscopic analysis, and finite element numerical simulation. A BBR double-layer structure blending model was developed to analyze the evolution of the low-temperature performance of recycled asphalt under full blending and the equivalent relationship of blending effects under different blending conditions. The diffusion characteristics of virgin and aged asphalt were analyzed based on FTIR using the BBR double-layer structure. A finite element model for the BBR test was constructed, and a correlation analysis between the results of the BBR macroscopic test and FTIR microscopic analysis was conducted. Results showed that the low-temperature performance of fully blended asphalt with different content followed the model: K mix = (1 -α ) K vir + αK age . Based on the recommended blending degree index (BOD S ), it was found that the blending of virgin and aged asphalt followed the time-temperature equivalence principle, and a blending master curve model was established. I S O was recommended to predict the aged asphalt content. During the early diffusion stage, a significant concentration gradient formed in the diffusion direction, with the maximum diffusion rate occurring at the interface. However, the concentration gradient gradually became uniform as diffusion progressed. Finite element analysis showed that the simulated results have a linear correlation coefficient of 0.91 with the experimental BBR values, validating the effectiveness of the BBR-FTIR macro-microscopic correlation analysis.