The A in Type IIIA refers to

• A. Air Entrainment
• B. Alkali resistance
• C. Aggregate size
• D. Admixture

Answer: (A)

Air entrainment is what the A signals. In Type IIIA cement, the high-early-strength cement is formulated to include air-entraining properties, creating a controlled network of microscopic air voids in the concrete. These tiny voids help relieve internal pressures during freezing and thawing, improving durability in cold climates and enhancing workability and slump retention without sacrificing too much strength. The other ideas don’t match what the A denotes: it isn’t about alkali resistance, aggregate size, or an external admixture designation—the A specifically identifies an air-entraining characteristic built into the cement itself.