What happens to the viscosity of asphalt binder as it ages?

As asphalt binder ages, its viscosity increases due to several physical and chemical changes that occur over time. Aging occurs from exposure to environmental factors such as heat, air, and UV radiation, which can lead to the oxidation of the binder. This oxidation process results in the formation of larger and more complex molecules, causing the binder to become thicker and more viscous.

The increase in viscosity affects the performance of the asphalt mixture, influencing its workability, adhesion, and resistance to deformation. In practical terms, higher viscosity means that the binder becomes less fluid, particularly in hotter conditions, which can impact the mixing and compaction processes that are crucial for achieving a high-quality pavement. Therefore, understanding the relationship between aging and viscosity is essential for asphalt inspectors and engineers to ensure proper material selection and long-term performance of asphalt pavements.