The additives used to enhance the performance of concrete for special purposes are called:

• A. Admixtures
• B. Fillers
• C. Chemicals
• D. Binders

Answer: (C)

Additives that modify concrete’s properties for specific performance are called admixtures. They are added to the mix in small amounts to achieve things like easier workability, controlled setting time, improved durability in freeze–thaw or sulfate conditions, reduced water demand, and better air void structure. This term is more precise than the others: fillers are inert materials used mainly to occupy space or adjust texture without changing the chemical nature of the mix; chemicals is too vague a label for the specialized products designed to alter concrete behavior; binders are the cementitious materials that actually bind the mix together, not the added performance modifiers.