What is used to increase the rate of hydration and strength development in concrete?

The correct choice is a set accelerator, which is specifically designed to increase the rate of hydration in concrete. When a set accelerator is added to the concrete mix, it helps to speed up the chemical reactions that occur as water interacts with cement particles, leading to an earlier setting time and, subsequently, faster strength gain.

This can be particularly beneficial in environments where quick turnaround times are needed, such as in cold weather conditions or when rapid construction schedules are in place. By facilitating the hydration process, set accelerators effectively enhance the early strength development of the concrete, making it suitable for situations where load-bearing capacity is required sooner than what would be achieved through standard curing practices.

In contrast, other additives like air entrainers, plasticizers, and water reducers serve different purposes. Air entrainers are used to improve the durability of concrete by creating tiny bubbles within the mix, which can help resist freeze-thaw cycles. Plasticizers, also known as water reducers, enhance workability without significantly increasing the water content, making the mix easier to handle but not necessarily speeding up hydration. Water reducers help maintain strength while reducing water, but they don't directly accelerate the setting time. Thus, while all these additives contribute to the quality and performance of concrete, a set accelerator is