In the context of asphalt, what does the term "compaction" refer to?

Compaction in the context of asphalt refers specifically to the mechanical process of densifying an asphalt mixture. This process is crucial for achieving the desired density and strength of the asphalt layer, which directly affects the performance and longevity of the pavement. During compaction, the air voids within the asphalt mixture are reduced, allowing the asphalt binder to distribute more evenly and effectively throughout the aggregate. Proper compaction helps to ensure that the pavement can withstand traffic loads, resist deformation, and maintain a smooth surface.

The other options describe different processes associated with asphalt paving. For instance, mixing asphalt with aggregates refers to preparing the materials before compaction, layering asphalt on a road relates to the application technique of the asphalt mixture, and cooling of asphalt refers to the temperature changes that occur after paving, but none of these capture the essence of what compaction specifically entails. Thus, understanding compaction as a distinct and critical process helps underscore its importance in achieving high-quality asphalt pavement.