Retarders are added to mortar to delay what aspect of the mixture?

Retarders are specifically added to mortar to delay the setting time of the mixture. This is crucial in various masonry applications as it provides additional working time with the mortar, allowing for adjustments and ensuring that the application is carried out smoothly.

The use of retarders can be particularly beneficial in hot weather conditions where the natural setting time of the mortar might be reduced due to higher temperatures. By slowing down the chemical reaction that occurs during hydration, retarders help maintain workability, allowing masons to position bricks or blocks without the mortar setting too quickly.

While the hydration rate, which refers to the speed at which the cement reacts with water, is affected by the presence of retarders, the primary purpose of these additives is to extend the amount of time the mortar remains workable before it begins to set. Thus, the correct association with retarders is primarily with setting time rather than merely the hydration rate, as they serve to extend the time before the mixture becomes unworkable.