According to Hawaii Building Code, what is the minimum concrete cover required for reinforcing bars in concrete exposed to seawater?
Correct Answer
B) 2.5 inches
The Hawaii Building Code requires 2.5 inches minimum concrete cover for reinforcement in severe exposure conditions such as direct seawater contact.
Why This Is the Correct Answer
Hawaii Building Code requires a minimum concrete cover of 2.5 inches for reinforcing steel in concrete directly exposed to seawater. This enhanced cover protects rebar from the accelerated corrosion caused by saltwater, which is a critical concern in Hawaii's marine environment.
Why the Other Options Are Wrong
Option A: 1.5 inches
Option A (1.5 inches) is incorrect. 1.5 inches is the minimum cover for interior slabs or concrete not exposed to weather. It is wholly inadequate for seawater exposure and would lead to rapid corrosion and structural failure in Hawaii's coastal conditions.
Option C: 2 inches
Option C (2 inches) is incorrect. 2 inches is the standard cover for concrete exposed to weather (but not seawater) under ACI 318. Seawater is a more severe exposure class that requires the additional half-inch — a detail that is easy to miss under exam pressure.
Option D: 3 inches
Option D (3 inches) is incorrect. 3 inches of cover is required for concrete cast against and permanently exposed to earth (such as footings). It is not the specific requirement for seawater exposure, though it exceeds the minimum.
Memory Technique
Seawater = 2.5 inches. Think: 2.5 is halfway between 2 (weather exposure) and 3 (earth exposure). Seawater sits between them in severity — more corrosive than rain, less abrasive than soil. The cover value mirrors the severity ranking: 2 < 2.5 < 3.
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