How does the size of aggregates affect concrete hydration?

The correct choice highlights that larger aggregates have less surface area, which in turn reduces the rates of hydration. This is significant in concrete mix design, as hydration is the chemical reaction between cement and water that leads to the hardening of concrete.

In concrete, the hydration process primarily occurs at the surface of the cement particles. Therefore, when larger aggregates are used, there is a reduced amount of surface area available for the interaction with water which can limit the overall hydration process. This affects how well the concrete can achieve its desired strength and durability properties, since proper hydration is essential for optimal bonding and development of the concrete structure.

Understanding this relationship is crucial for technicians when designing concrete mixes, as varying the size of aggregates can aid in controlling hydration rates and ultimately affect the performance of the concrete in application.