Introduction
Bitumen is a kind of solid petroleum that is used widely in the asphalt and also used in other construction materials. Bitumen reacts with oxygen or air moisture to produce oxidative softening properties that improves its flexibility, which makes it desirable in various construction applications. The variation of bitumen properties is being affected by many factors like source of bitumen, the production process, quality and technology of application, the environment and so on. Therefore, analyzing the structural properties of bitumen has been widely accepted as an important measure for characterizing the differences among bitumen samples.
Structural analysis can be conducted by both optical and electron microscopic methods for bitumen. The main objective of a structure analysis is to provide quantitative information about the size and distribution of the bituminous particles within a sample. An optical microscope needs traditional radiographic methods for analysis, and a finer resolution is obtained with the use of an electron microscopy. The results from the optical microscopic method can be used as reference data in order to compare with those obtained by any electron microscopic technique.
Optical Characterization of Bitumen
Optical methods are mostly based on measurement of the bituminous particles. This method requires the development of samples in thin layers with liquid emulsions or solvents, followed by examination under a polarized light microscope. For example, light microscopy is done with a polarized light source and a vertical stage which is used to rotate the sample. A negative image of the sample is obtained that provides a better contrast between the dispersed bitumen particles and the binder.
In order to measure the optical characteristics of bitumen such as particle size, size distribution and particle shape, a special instrument such as an image analyzer can be used. The image analyzer is able to measure all these aspects directly from the microscopic images of the surface of the bitumen sample. The results from the image analyzer can be used to compare the bitumen samples and to determine the differences between them.
Electron Microscopy of Bitumen
Electron microscopy is a powerful technique for analyzing the structural properties of bitumen. The electron microscopic technique provides greater resolution and has been used in many studies for the structural analysis of bitumen. This method is used to characterize the size and shape of the bituminous particles by using a scanning electron microscope (SEM).
For the structural analysis of bitumen, the SEM is equipped with an electron detector which is used to detect the electrons emitted from the bitumen sample. This method has been used to determine the size, shape, size distribution and the surface characteristics of the bituminous particles. The SEM also can provide information about the internal structure of the bitumen and its microstructure. In addition, the SEM technique has been used to investigate the cement and binder content of the bitumen samples.
Conclusion
Bitumen is an important component in the construction materials and its quality is determined by the variation of its properties. Structural analysis of bitumen can be done by both optical and electron microscopy techniques. Optical methods are mainly used to measure the optical characteristics of bitumen such as particle size, size distribution and particle shape. For the structural analysis of bitumen, electron microscopy provides greater resolution and can be used to characterize the size and shape of the bituminous particles, the surface characteristics and cement and binder content of the bitumen sample.
