Admixture

An admixture is any ingredient — other than cement, water, and aggregate — added to a concrete batch before or during mixing to change its fresh or hardened properties. Common categories include water reducers, air-entraining agents, accelerators, retarders, and superplasticizers.

Admixture dosage is specified as a percentage of cement weight and recorded on the batch ticket, since over- or under-dosing can significantly change set time, strength, or workability.