What is the effect of aging on asphalt binder?

Aging of asphalt binder refers to the changes that occur in its chemical and physical properties over time, particularly when exposed to environmental conditions such as heat, oxygen, and ultraviolet light. As asphalt binder ages, the volatile components evaporate, and the binder undergoes oxidation. This process leads to a significant increase in viscosity, making the material stiffer and less workable.

The increase in viscosity is primarily due to the formation of larger molecular structures within the binder as the smaller hydrocarbon molecules are oxidized and reactive components are transformed. Additionally, the aging process can result in a reduction in the binder’s flexibility, leading to a propensity for cracking and brittleness, particularly under lower temperature conditions or applied stress.

Thus, the correct answer identifies that aging increases viscosity and can lead to brittleness, which is crucial for understanding the long-term performance of asphalt materials in pavement applications. This knowledge helps in making informed decisions regarding maintenance and rehabilitation of asphalt pavements.