concrete admixture

admixture

A material other than water, aggregates, lime, or cement, used as an ingredient of concrete or mortar, and added to the batch immediately before or during its mixing; used as a water repellent, as a coloring agent, as a retarder or accelerator (to modify its setting rate), etc.

McGraw-Hill Dictionary of Architecture and Construction. Copyright © 2003 by McGraw-Hill Companies, Inc.