1. n. [Well Completions]

Chemicals and materials added to a cement slurry to modify the characteristics of the slurry or set cement. Cement additives may be broadly categorized as accelerators, retarders, fluid-loss additives, dispersants, extenders, weighting agents, lost circulation additives, and special additives designed for specific operating conditions. Cement additives are commonly available in powder or liquid form, enabling some flexibility in how the cement slurry is prepared.

See: cement accelerator,  cement dispersant,  cement extender,  cement retarder,  fluid-loss additive