What is the required concrete strength for residential foundations in Hawaii's seismic and coastal environment?
Correct Answer
D) 4,000 psi minimum
Hawaii requires 4,000 psi minimum concrete strength for foundations to resist both seismic loads and chloride penetration from coastal exposure.
Why This Is the Correct Answer
The correct answer is 4,000 psi minimum. Hawaii's Building Code requires 4,000 psi minimum compressive strength for residential foundations due to the combined demands of seismic loading and coastal chloride exposure. Higher strength concrete is inherently less permeable (fewer capillary pores), providing better resistance to chloride penetration, while also delivering the structural capacity needed to resist earthquake-generated forces transmitted through the foundation system.
Why the Other Options Are Wrong
Option A: 2,500 psi minimum
2,500 psi is a minimum strength acceptable for interior concrete elements or plain concrete not exposed to aggressive environments. It is far below what Hawaii requires for foundations, as it produces highly permeable concrete with insufficient durability for coastal conditions and inadequate strength for seismic loads.
Option B: 3,000 psi minimum
3,000 psi is a common minimum for standard residential construction in many non-coastal, non-seismic jurisdictions. It does not meet Hawaii's elevated requirements for foundations exposed to both seismic forces and marine chloride attack.
Option C: 3,500 psi minimum
3,500 psi is closer but still below Hawaii's 4,000 psi foundation requirement. While 3,500 psi may be sufficient for some structural applications in less aggressive environments, Hawaii's combination of seismic and coastal exposure demands the higher 4,000 psi minimum.
Memory Technique
Hawaii foundations = 4,000 psi. Think of Hawaii's '4' threats: (1) seismic, (2) coastal chloride, (3) hurricanes, (4) corrosion — and the 4 in 4,000 ties them together. Alternatively: 4,000 psi = 4 ksi = a round, memorable number for a high-performance environment.
More Hawaii Questions
A concrete mix design for coastal construction specifies a water-cement ratio of 0.40. If 650 lbs of cement is used per cubic yard, how many gallons of water should be added?
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Which roofing attachment method is specifically required in Hawaii's hurricane zones for asphalt shingles on residential construction?
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