According to Hawaii Building Code, what is the required minimum rebar cover for concrete slabs exposed to salt air?
Correct Answer
B) 2 inches
Hawaii requires minimum 2-inch concrete cover over reinforcement in salt air environments to protect against corrosion from chloride exposure.
Why This Is the Correct Answer
The correct answer is 2 inches. Hawaii Building Code mandates a minimum 2-inch concrete cover over reinforcing steel in salt-air environments. This extra cover (compared to interior slabs which may require only 3/4 to 1.5 inches) creates a thicker barrier that slows chloride ion migration from salt air to the rebar, significantly delaying the onset of corrosion.
Why the Other Options Are Wrong
Option A: 2.5 inches
2.5 inches is more than the code minimum and while it would provide additional protection, it is not the specified requirement. Specifying more than required adds unnecessary cost and weight without a code basis.
Option C: 1.5 inches
1.5 inches is the minimum cover often used for interior or protected concrete elements. It is insufficient for salt-air exposure because chloride ions penetrate the thinner cover too quickly, initiating corrosion within the service life of the structure.
Option D: 1 inch
1 inch of cover is used for concrete cast against and permanently exposed to earth in some codes, not for salt-air slabs. At only 1 inch, chloride diffusion to the rebar would be rapid, causing early corrosion and structural degradation.
Memory Technique
Think '2 inches for 2 sides of Hawaii's threat': salt from the ocean and sun. The number 2 appears everywhere in Hawaii coastal concrete: 2-inch cover, 2000+ miles from the mainland. Two inches = coastal protection.
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