Which factor primarily influences the selection of aggregate types in asphalt mixtures?

The selection of aggregate types in asphalt mixtures is primarily influenced by traffic load and environmental conditions. This is crucial because aggregates must provide the appropriate structural support and durability that align with the expected stresses from vehicle loads and the specific climate where the asphalt will be placed.

For instance, areas with heavy traffic require aggregates that offer excellent strength and stability to withstand significant pressures, while regions subject to freeze-thaw cycles might benefit from aggregates with lower absorption rates and better resistance to weathering. Additionally, environmental conditions such as temperature and moisture can dictate the performance requirements of the asphalt mixture, leading to the choice of aggregates that can maintain their integrity under these conditions.

While cost, size, and aesthetic factors are important considerations in the overall selection process, they do not directly dictate the structural and performance requirements that aggregates must meet in relation to the demands of traffic and the environment. Focusing on traffic load and environmental conditions ensures that the asphalt mix will perform effectively throughout its intended life cycle.