What are the materials called that are mixed with cement other than cement, sand, or aggregate?

The term applied to materials mixed with cement, aside from cement, sand, or aggregate, is "admixtures." Admixtures are substances added to concrete or mortar to enhance specific properties of the mix. These can include substances that improve workability, speed up curing, reduce water content, increase durability, or impart other specific characteristics to the concrete.

Using admixtures allows for more control over the properties of the cement mix, making it possible to achieve desired performance aspects for various applications in construction. For example, chemical admixtures can alter the rate of hydration, which affects setting times and final strength.

The other terms listed do not accurately describe this function. Modifiers typically refer to alterations in material rather than specific additions to a mix. Composites denote materials made from two or more constituent materials that remain distinct upon forming, and fillers generally refer to materials used to fill spaces that do not specifically enhance the core properties of the concrete in the way admixtures do.