Confocal Laser Scanning Microscopy - Observation of the Microstructure of Bitumen and Asphalt Concrete

Confocal Laser Scanning Microscopy (CLSM) has gathered interesting new results regarding the microstructure of bitumina as part of a comprehensive study on bitumen and asphalt concrete. Compared to normal fluorescence microscopy, the CLSM technique has been proven to be the method of choice for bitumen. The main advantage is a much stronger fluorescence signal due to the higher intensity of the excitation laser, which is higher by several orders of magnitude compared to conventional lamps (e.g. Mercury-vapour lamps). Also, the smaller aperture used to scan the surface creates much better special resolution. Since the definition and improvement of asphalt concrete is the great challenge the ever rising expectations and requirements of roadworks puts in front of the bitumen industry. Thus, the search for techniques allowing an assessment of the adhesive and rheological properties of bitumen is very essential. The CLSM technique makes the detailed observation of the fluorescent centres in bitumen accessible, and thus provides important information on the microstructure and on the asphaltene micelles. Additionally, it is possible to observe the changes implied by the introduction of mineral aggregates into the bitumen, and thus to draw conclusions about the interaction of bitumen and the mineral components inside the asphalt concrete. Especially for polymer modified bitumina these experiments have shown intriguing results regarding structural phenomena that influence and practically define their improved mechanical properties.