Commercial Building Inspector B2Floor ConstructionHard
A commercial building inspector is reviewing the design for a new multi-story parking garage. The plans indicate that the concrete floor slabs are designed as two-way slabs. According to ACI 318, what is the minimum concrete cover required for primary reinforcement bars in a two-way slab not exposed to weather or in contact with the ground?
- A1 inch
- B3/4 inch
- C1/2 inch
- D1 1/2 inches
Show answer & explanationAnswer & explanation
Correct answer: B. 3/4 inch
According to ACI 318, for slabs, walls, and joists not exposed to weather or in contact with the ground, the minimum concrete cover for primary reinforcement is 3/4 inch (19 mm). This ensures adequate bond and fire protection.
Why the other options are wrong
- A. 1 inch cover is often required for beams and columns, or for slabs exposed to weather, but not for interior slabs.
- C. 1/2 inch is typically for #5 bars and smaller in slabs, walls, and joists where not exposed to weather or in contact with ground, but 3/4 inch is more common for general primary reinforcement.
- D. 1 1/2 inches is typically required for concrete cast against earth or for larger diameter bars in beams and columns exposed to weather.
ACI 318 Concrete Cover (Interior Slabs)
The minimum distance from the surface of the concrete to the outermost steel reinforcement, as specified by ACI 318, for interior slabs.
- Ensures bond between concrete and steel.
- Provides fire protection for reinforcement.
- Protects against corrosion.
Memory trick: For interior slabs, 3/4 inch is the concrete's armor.