Which factor has the greatest effect on the time available for compaction?

The time available for compaction in hot mix asphalt (HMA) primarily depends on lift thickness. When the lift thickness is greater, the volume of material that needs to be compacted increases, which consequently extends the duration required for adequate compaction. Thicker lifts retain heat longer, allowing for more optimal compaction conditions initially; however, once the material begins to cool, it becomes more difficult to compact effectively. Therefore, the lift thickness plays a crucial role in determining the timeframe within which effective compaction can be achieved, as larger lifts can significantly impact the cooling rate of the asphalt during the compaction process.

While factors such as air and base temperature, and wind speed also influence the cooling rate and compaction time, they do not have the as significant an impact on the overall available time for compaction as lift thickness does. Lift thickness directly relates to the volume of material and its ability to retain heat, which is why it is considered the most critical factor in this context.