Microscopic Observation of Absorption of Asphalt Binder into the Aggregate Pores Using SEM

In this study, an experimental scheme is developed to visualize asphalt binder absorption within aggregate pores using scanning electron microscopy. A suitable sample preparation approach, image magnification levels, and image processing techniques are utilized for the visualization of the aggregate pores (pore structure and binder occupancy) before and after adding asphalt binder. Three types of aggregate—gneiss, quartzite, and sandstone—are used in this study. The results indicate that sandstone exhibits maximum binder absorption, followed by gneiss, and then quartzite. Sandstone also shows the highest pore occupancy, indicating that a higher pore area enables more binder absorption. Further, the study highlights a progressive decrease in the absorption level as one moves from the aggregate boundary toward its interior.