Air voids in concrete can reduce the requirements of which component?

• A. Increase water usage
• B. Increase fine aggregate requirements
• C. Reduce fine aggregate requirements
• D. Have no effect

Answer: (C)

Air voids increase the porosity of concrete, so part of the mix volume is occupied by air rather than solid material. Because of that, the solid portion that must be filled by cement paste and aggregates is reduced, allowing you to use less fine aggregate to achieve the same overall volume and workability. This is why air voids can lead to a reduced fine aggregate requirement. Keep in mind that introducing more air voids lowers density and strength, so this adjustment isn’t free of trade-offs and is typically managed to balance durability and performance.