Which of the following is NOT a factor in the "Environmental conditions" affecting compaction?

The correct answer indicates that the type of binder used is not considered an environmental condition affecting compaction. Environmental conditions typically encompass factors that can influence the effectiveness of compaction processes at the site.

Temperature plays a crucial role in compaction because it affects the materials' workability. For instance, hotter temperatures can make asphalt more pliable, while colder temperatures can cause the materials to become too rigid, impacting how easily they compact.

Moisture is another vital environmental factor, as it can either enhance or hinder compaction. The presence of too much moisture can lead to a muddy, unstable base, while insufficient moisture can make materials dry and less cohesive.

Wind speed, while less influential than temperature and moisture, can also impact compaction, particularly for asphalt paving. High winds can lead to rapid cooling of asphalt materials, adversely affecting their workability and compaction timing.

In contrast, the type of binder, while essential for the properties of the mix and the overall quality of the pavement, does not fall under the category of environmental conditions. Instead, it is a material characteristic that influences the performance of the compacted layer rather than external factors that impact the compaction process itself.