What effect does a high air void content have on an asphalt mixture?

A high air void content in an asphalt mixture leads to increased susceptibility to moisture damage. This is primarily because high air voids create spaces within the asphalt that allow water to infiltrate. When water enters these voids, it can weaken the bond between the asphalt binder and aggregates, leading to deterioration of the pavement structure over time.

Furthermore, the presence of excess air voids can result in a less dense mixture overall, which may negatively impact the mixture's ability to withstand stresses from traffic loads and environmental conditions. This susceptibility to moisture damage is particularly concerning in climates that experience freeze-thaw cycles, as water can freeze in the voids, causing cracks and pavement distresses.

In contrast, the other options suggest beneficial outcomes for high air void content, which do not align with the reality of asphalt performance. Increased durability, reduced aging, and improved strength are typically associated with optimal air void content in asphalt mixtures, rather than high void levels. Thus, the correct answer reflects the negative impact of high air void content on the longevity and integrity of asphalt pavements.