As per the classification, all chemical admixtures fall under ASTM designation _________.

• A. C494
• B. C260
• C. C618
• D. C595

Answer: (A)

Chemical admixtures for concrete are governed by ASTM C494, the standard specification for chemical admixtures for concrete. This standard covers the additives used to modify workability, set time, early strength, and other concrete properties, and it defines how these products are classified, tested, and labeled to ensure compatibility with cement and aggregates. The reason this is the best answer is that C494 is the umbrella standard specifically dedicated to chemical admixtures, whereas the other designations refer to different material categories: C260 covers air-entraining admixtures specifically, C618 addresses fly ash as a mineral admixture, and C595 covers blended hydraulic-cementitious materials. So for chemical admixtures as a whole, the ASTM designation is C494.