Importance of air void in flexible pavement
Air void content of bituminous material is an important control parameter for the quality of bitumen being laid and deposited. If the air void content is too high, it allows infiltration of air and water. In addition, it also increases the hardening rate of binders that cause premature brittleness of the pavement. In addition, too much void material will also cause differential compaction under traffic load and result in the formation of ropes and grooves along the wheel track.
However, a minimum amount of air void must be maintained to avoid instability during the compaction process and to provide room for bitumen flow in long-term consolidation under traffic loads. Sufficient air voids should be designed to allow for expansion of the binder in summer and for compaction by road traffic, otherwise bleeding and loss of stability may occur and the pavement will deform easily under severe load.