What is the air content specification for concrete intended for bridge decks?

The air content specification for concrete intended for bridge decks is crucial for ensuring the durability and long-term performance of the concrete in varying environmental conditions, particularly exposure to freeze-thaw cycles. A specification of 3 to 5% air content helps to provide adequate air voids within the concrete without compromising its structural integrity.

Maintaining the air content within this range allows the concrete to resist damage caused by expanding ice during freezing, thereby improving its durability. Air-entrained concrete reduces the risk of spalling and cracking, essential in structures like bridge decks that are often exposed to moisture and temperature fluctuations.

This range balances the need for workability during placement and the requirements for strength and durability. Higher air content percentages, as suggested in other options, could lead to decreased strength or increased porosity, which would not be suitable for a bridge deck's demanding applications.