Peiliang Cong

This study proposes a method for separating asphalt and aggregates in recycled asphalt pavement (RAP) materials using surfactants as solvents. This method utilizes surfactants to soften the asphalt by reducing its surface tension, separating the RAP clusters, and washing away the asphalt from the RAP. The wastewater is recycled during the emulsification–separation process without discharge. Factors affecting the separation effect of RAP, including the type of anionic surfactants, the surfactant concentration, the emulsion-to-RAP ratio, temperature, the rotation rate and time, and the RAP’s particle size, were investigated in depth, and the separation effect and its influence on the aggregate properties were evaluated. The experimental results indicate that when using the optimal process to mix and treat 13.2 mm and 9.5 mm RAP clusters, it is possible to achieve 100% separation of the coarse RAP above 4.75 mm, with a 64.58% reduction in the asphalt content. The angularity of the aggregate remained unchanged after separation. It was observed from scanning electron microscopy (SEM) images that the asphalt on the surface of the coarse aggregate had been eluted, and the morphology of the aggregate surface was completely exposed. This environmentally friendly separation method provides new possibilities for high-content RAP recycling in pavement engineering.

Firstly, thermoplastic polyurethane recycled material (TPRM) particles were used to prepare modified asphalt. Then, the modified asphalt’s physical properties were investigated. The results show that the TPRM particles improved its high-temperature performance, low-temperature crack resistance, and shear behavior due to its increased cohesion and low-temperature fracture energy levels. Thermal susceptibility was affected by the degree of swelling and dissolution of the TPRM particles, the composition of the asphalt, and the interface effect between the asphalt molecules and both the regular and slender–irregular TPRM particles. The TPRM particles swelled and dissolved after absorbing the light components of asphalt. Changes in the shearing temperature and time made the TPRM particles swell and dissolve more than changes in the activation temperature and time. An increase in the shearing/activation temperature and time increased the hydrogen bond content in the modified asphalt due to the rearrangement of the polyurethane’s molecular structure and the hydrogen bonds formed by the asphaltene and polyurethane molecules. Slender–irregular TPRM and “sea–island” and hilly and gulley structures were found in the modified asphalt matrix.