Effects of different carriers for zinc oxide (ZnO) particles on microstructure of ZnO/layered silicate composite and aging resistance of composite modified asphalt

Abstract

• ZnO/layered silicate composite with three different carriers is synthesized. • Adding EVMT can significantly weaken agglomeration effects of ZnO particles. • Introducing ZnO particles can enhance UV absorption ability of layered silicates. • Exfoliated phase structure is formed in ZnO/MMT or ZnO/EVMT modified asphalt. • EVMT and REC are preferable to form composite and improve asphalt aging resistance. With the use of nanocomposite synthesis operations, the produced zinc oxide/expanded vermiculite (ZnO/EVMT) composite, a combination of ZnO particles and EVMT, has ZnO particles of the weakened agglomeration effects and can comprehensively improve the resistance of asphalt to thermo-oxidative and ultraviolet (UV) aging. However, the effects of different carriers for ZnO particles on the microstructure of ZnO/layered silicate composite and aging resistance of the composite modified asphalt are still unknown. In this research, three ZnO carriers, montmorillonite (MMT), expanded vermiculite (EVMT) and rectorite (REC), were employed to support ZnO particles (named ZnO/MMT, ZnO/EVMT and ZnO/REC, respectively). Then, the microstructure of different ZnO/layered silicate composites was investigated by field emission scanning microscope (FESEM), X-ray diffractometer (XRD) and UV–visible spectrometer (UV–vis) tests. Finally, the effects of different carriers on the morphology, phase structure, storage stability, physical properties and aging resistance of ZnO/layered silicate composite modified asphalt were discussed. Results showed that with the unique layered structure and its integrity, the three carriers are feasible to synthesize ZnO/layered silicate composite, and ZnO particles are supported or embedded on the surface of layered silicate sheets and have weaker agglomeration effects. Except for ZnO/MMT composite, the other two composites have sufficient composition connection strength. The exfoliated phase structure is formed in the ZnO/MMT or ZnO/EVMT composite modified asphalt systems. Additionally, the three ZnO/layered silicate composites have good asphalt compatibility and storage stability in asphalt, especially for ZnO/REC composite. The addition of ZnO/layered silicate composites into asphalt slightly influences physical properties of asphalt. Incorporating ZnO/layered silicate composites, regardless of the types, into asphalt could comprehensively enhance the resistance of asphalt to thermo-oxidative and UV aging. Comparatively, EVMT and REC are preferable to support ZnO particles and generate ZnO/layered silicate composite and comprehensively improve the aging resistance of asphalt.