Which component is key in preventing water infiltration in asphalt layers?

The asphalt binder serves as the essential component in preventing water infiltration in asphalt layers. It acts as a glue that binds the aggregate particles together, creating a cohesive and impermeable surface. When properly applied, the binder fills the voids between the aggregates, which helps eliminate pathways for water to seep through.

The integrity and quality of the binder are critical, as it influences the durability and flexibility of the asphalt mix, allowing it to withstand environmental stresses while maintaining a waterproof barrier. A well-designed asphalt mix that contains sufficient binder will be more resistant to water damage, leading to a longer-lasting pavement surface.

While other materials like organic additives, aggregate texture, and silica sand may play supportive roles in enhancing certain properties of the mix, they do not primarily serve the function of preventing water infiltration to the same extent as the asphalt binder does.