Study on the Adhesion Characteristics of Asphalt-Aggregate Interface in Cold Recycled Asphalt Mixtures

The reclaimed asphalt pavement materials have been used for sustainable cold-recycling, significantly benefiting air quality and resource conservation, while its microscale interface properties greatly affected road performance during the cold-recycling processes. In this investigation, the cold recycled asphalt mixtures were prepared with different mixing proportions, considering the effects of cement content and mixing water amount. The adhesion characteristics of the asphalt-aggregate interface in different cold recycled asphalt mixtures have been comprehensively investigated based on the atomic force microscopic (AFM). The microscale morphology and the adhesion properties, including roughness, inclination angle, adhesion force, Derjaguin–Muller–Toporov (DMT) modulus, and dissipated energy were evaluated at the interface and noninterface regions. The micromorphology results showed that the addition of cement could enhance the roughness and inclination in interface regions. In addition, the content of mixed water showed the most significant effect when the water amount was 80%. The results showed that the adhesion force, DMT modulus, and dissipated energy increased with the addition of cement, indicating that the cement could improve the microscale mechanical properties of cold recycled asphalt mixtures. With the increase of mixing water content, the adhesion characteristics showed varied results, and the optimum water content of 80% contributed to the adhesive properties. In addition, the adhesion force, DMT modulus, and dissipated energy were all higher in the interface region by comparing with the noninterface region. The correlations between the macroscale splitting tensile strength and microscale adhesion characteristics of cold recycled asphalt mixtures were established.