What is the typical minimum concrete cover to reinforcement for exterior slabs in moderate exposure?

• A. About 2 inches (50 mm).
• B. About 1 inch (25 mm).
• C. About 4 inches (100 mm).
• D. About 6 inches (150 mm).

Answer: (A)

Concrete cover to reinforcement is the distance from the outer surface of the concrete to the outer surface of the reinforcing steel. This cover protects the steel from moisture, chemicals, and freeze–thaw effects, helps ensure proper bond, and contributes to fire resistance.

For exterior slabs in moderate exposure, the standard minimum is about 2 inches (50 mm). This thickness puts the rebar well back from the surface to limit moisture and chloride penetration and to reduce the risk of corrosion and subsequent cracking. Using less cover would shorten the life of the reinforcement by making it more susceptible to deterioration; using more cover adds cost and may be unnecessary for this exposure level. In harsher environments (like marine exposure or where de-icing salts are common), greater cover would be required.