What is a key factor in the performance of concrete or asphalt?

The moisture content of aggregates plays a crucial role in the performance of concrete or asphalt. Proper moisture levels in the aggregates are essential for achieving the desired workability, strength, and durability of the final product. If aggregates are too dry, they can absorb water from the mix, leading to an insufficient amount of water available for hydration of the cement or bonding in the asphalt, which can compromise the integrity of the concrete or asphalt. Conversely, excessive moisture can lead to issues such as segregated or overly fluid mixes, affecting workability and ultimately leading to performance problems like cracking or a decrease in strength.

The other factors, while important in their own right, do not impact performance as significantly as moisture content. For instance, the chemical composition of the cement influences various properties of concrete, but it does so indirectly in relation to the aggregates' moisture. The color of the aggregate materials may affect aesthetic properties but has minimal impact on structural performance. Lastly, while air can be beneficial in controlled amounts (as in air-entrained concrete for freeze-thaw resistance), excessive air can weaken the structure. Hence, moisture content is a more direct key factor influencing the overall performance of the mixture.