Effect of Sasobit warm mix on micro properties of asphalt with different degrees of regeneration

In this work, an aged asphalt was mixed with a new modified asphalt based on styrene–butadiene–styrene (SBS) in different proportions, and the warm mixing agent was added to simulate the asphalt fusion behaviour in the warm mixed recycled asphalt with different aged asphalt fertilizer (reclaimed asphalt pavement, RAP) content. Low field nuclear magnetic resonance (LF-NMR), atomic force microscopy (AFM), and Fourier transform infrared spectroscopy (FTIR) were used as analytical techniques to study the role of the warm mixing agent in terms of molecular bond energy, apparent morphology, and functional groups. It was found that the softening point and penetration of asphalt are reduced, and the ductility is increased, during the regeneration process. Sasobit warm mix agent can reduce the penetration and ductility of asphalt and improve the softening point. Its viscosity reduction effect is mainly achieved by adsorbing saturated components and decreasing the bond energy between 1H and other molecules; Sasobit warm mix agent can improve the aging state of mixed asphalt. On the AFM two-dimensional adhesion diagram, the number of bee-shaped structures and the single area is reduced; in the new and old mixed asphalt, the greater the proportion of new asphalt, the more evident the effect of Sasobit warm mix agent is.