What are the materials added to concrete or mortar to change its properties called?

The correct term for materials added to concrete or mortar to enhance or modify their properties is "admixtures." Admixtures can include a variety of substances that serve different functions, such as improving workability, accelerating or retarding setting time, enhancing durability, or changing the color or strength of the concrete.

Admixtures are crucial for achieving specific performance characteristics in concrete and mortar mixes, enabling builders to adjust the material properties for various environmental conditions and application requirements. For instance, if a fast-setting concrete is needed for a winter construction project, an admixture that accelerates the curing process would be utilized.

In contrast, additives generally refer to materials that may be introduced in smaller proportions to provide a certain function but are not classified explicitly as admixtures in the context of concrete. Aggregates are the granular materials mixed with cement and water to form concrete, while cement types pertain to the different kinds of cement available, each with unique properties suitable for specific applications. These terms do not accurately describe the function of modifying the properties of concrete or mortar.