Morphology and properties changes of virgin and aged asphalt after fusion

Abstract

The aging of asphalt seriously affects the pavement performance of asphalt mixtures. In this study, we investigated the changes in virgin and aged asphalt during the regeneration process of aging asphalt using atomic force microscopy (AFM), Fourier transform infrared (FTIR) spectrometer, and dynamic shear rheometry (DSR). Dynamic modulus tests were carried out for asphalt mixtures containing 30% and 50% reclaimed asphalt pavement. Comparatively DSR tests were performed to determine the complex shear modulus for asphalt binder blends containing 30.6% and 51% aged asphalt. Based on the Hirsch model, the predicted and measured values of the dynamic modulus were compared to obtain a macroscopic evaluation of the degree of virgin and aged asphalt fusion. The results show that the virgin and aged asphalt are fused with high uniformity. From AFM scans, with increase in virgin asphalt content, the size of the bee-like structure decreased and the number increased. This was reflected in roughness indexes (Rq, Ra, Pbee-like, and Rmax) exhibiting gradually decrease, tending more to the microstructure of virgin asphalt with increasing virgin asphalt content. FTIR results showed that the carbonyl index and sulfoxide index decreased as the virgin asphalt content increased, which was consistent with the AFM test results. With addition of an optimal amount of regenerant the microstructure and high-temperature rheological properties of aged asphalt were positively altered. The improvement in the microstructure and rheological properties of rejuvenated aged asphalt was found to be similar to that of blends altered with 49% of virgin asphalt. With the increase in the content of virgin asphalt, the complex shear modulus of the asphalt G*, the rutting resistance of asphalt G*/sinδ was found to decrease as δ increased. The comparison between the predicted and measured dynamic modulus value confirms the successful fusion of the virgin and aged asphalt from a macro perspective. The macroscopic and microscopic analysis results of the change law of virgin and aged asphalt fusion are consistent.