Synthesis, characterization and utilization of zinc oxide/expanded vermiculite composite for bitumen modification

The multi-dimensional nanomaterial modifier composed of nano-zinc oxide (nano-ZnO) and expanded vermiculite (EVMT) can significantly improve resistance to thermo-oxidative and ultraviolet radiation aging and road performances of bitumen. However, the nano-ZnO particles are susceptible to agglomeration and the homogeneity between nano-ZnO particles and EVMT is hard to be achieved in bitumen. In the study, a new bitumen modifier, a combination of ZnO particles and EVMT, was developed by composite technology to reduce or avoid the agglomeration of the ZnO particles and generate a synergistic effect on bitumen properties, especially for the aging resistance of bitumen. The newly developed modifier was synthesized with a modified hydrolytic precipitation method and characterized by X-ray diffractometer (XRD), field emission scanning microscope (FESEM), Fourier transform infrared spectrometer (FTIR), and UV-Visible spectrometer. Further, the modified bitumen was prepared and then aged with thin-film oven aging test (TFOT), pressure aging vessel (PAV), and ultraviolet (UV) radiation aging methods, respectively. Finally, the effects of modifiers on physical, rheological, and aging resistance of bitumen were evaluated. Results showed that with the synthesis operation, ZnO particles homogeneously loaded on the surface of EVMT, greatly restraining ZnO particles agglomeration and achieving the homogeneity between ZnO and EVMT. Furthermore, due to higher softening point, ductility, and complex modulus values for the modified bitumen compared with that of unmodified bitumen, the introduction of the newly developed modifier can potentially enhance the low-temperature tensile properties and deformation resistance of bitumen. Meanwhile, when the bitumen is exposed to various environmental factors, such as heat, oxygen, and UV radiation, the composites modifier in bitumen can synergistically play a role in reducing the effects on bitumen aging. For that, regardless of aging methods, the introduction of ZnO/EVMT into bitumen can efficiently retard its softening point increase and mobility deterioration, namely, hinder bitumen aging. Therefore, the newly developed modifier, ZnO/EVMT, is promising in both resisting bitumen aging and improving bitumen properties at low and high temperatures, and thus a longer service life for bitumen pavement can be expected with its application.