SEM and ESEM techniques used for analysis of asphalt binder and mixture: A state of the art review

This paper reviews techniques and analyses performed on microstructure of the asphalt binder and mixture using Scanning Electron Microscopy (SEM) and Environmental Scanning Electron Microscopy (ESEM). An extensive insight on the SEM and ESEM principle and techniques, different sample preparation methods and instrument techniques for capturing the micromorphology of the binder and mixture have been presented. The difference between SEM and ESEM in terms of challenges and limitation regarding the analysis of bitumen has been explained. In depth discussions on the surface properties, fracture morphology, network structure, dispersion, phase morphology, structural and strength mechanism, adhesion, deform mechanism and the formation of fibril structures of asphalt binder and mixture have been provided. Recommendations and useful techniques are outlined for future research to obtain any correlation between the microstructure and physical/rheological properties of the asphalt binder/mixture.