Effect of multi-dimensional nanomaterials on the aging behavior of asphalt by atomic force microscope

The decline in properties of asphalt due to thermal-oxidative aging and photo-oxidative aging seriously affects the service life of pavement. Multi-dimensional nanomaterials composed by organic expanded vermiculite (OEVMT) and surface modified nanoparticles (nano-ZnO, nano-SiO2 or nano-TiO2) as an anti-aging composite modifier was used to improve anti-aging behavior of asphalt. The aging methods included thin film oven test (TFOT), pressure aging vessel (PAV) test and ultraviolet (UV) aging. The aging behavior and mechanism of asphalt were investigated by Peak force quantitative nanomechanical mode (PFQNM), a kind of Atomic force microscope (AFM) modes that can measure the topography, roughness, adhesion and Young's modulus simultaneously. AFM PFQNM results show that bee-like structure is destroyed, and the dispersed phase dramatically changes after adding modifiers, while the number of bee-like structures of modified asphalt is increased after TFOT aging. Compared with the control group, increased roughness and adhesion and reduced Young's modulus of modified asphalt prove that multidimensional nanomaterials could prevent asphalt aging effectively. Among the three modifiers, OEVMT + nano-ZnO shows the better improvement in aging resistance of asphalt by displaying lower Young's modulus and higher adhesion values than OEVMT + nano-TiO2 and OEVMT + nano-SiO2, and nano-ZnO possesses the best compatibility with asphalt among three types of inorganic particles. In addition, there is a strong correlation between adhesion and Young's modulus, and its correlation coefficient is -0.87. Furthermore, the correlation degree between microstructure and physical parameters is investigated by grey relational analysis. It is proved that the microstructure can be used for the characterization of asphalt performance. (C) 2020 Elsevier Ltd. All rights reserved.