The structural drawings specify f'c but do not name a different test age. For standard-cured cylinders used to verify f'c, the default ACI test age is which one?
Correct Answer
B) 28 days
ACI 318 strength acceptance is based on the specified compressive strength at 28 days unless another test age is designated, so the default verification age is 28 days. Other choices: 7 days is often used for early information, 56 days can be specified for some mixtures, and 90 days is not the default f'c age.
Why This Is the Correct Answer
ACI 318 strength acceptance is based on the specified compressive strength at 28 days unless another test age is designated, so the default verification age is 28 days.
Why the Other Options Are Wrong
Option A: 7 days
In concrete work, 7 days is the wrong selection for Standard test age: 7 days is a different published number than the cited Standard test age value; ACI 318-19 Ch. 2 definition of f'c and 26.12 strength testing supports 28 days.
Option C: 56 days
Choice C gives 56 days. Its specific error: 56 days is a different published number than the cited Standard test age value; ACI 318-19 Ch. 2 definition of f'c and 26.12 strength testing supports 28 days. The accepted answer is 28 days.
Option D: 90 days
Choice D (90 days) is rejected because 90 days is a different published number than the cited Standard test age value; ACI 318-19 Ch. 2 definition of f'c and 26.12 strength testing supports 28 days. The cited answer is 28 days.
Memory Technique
Make standard test age a tabbed card: cite the exact condition, then choose 28 days.
Reference Hint
Open ACI 318-19, Building Code Requirements for Structural Concrete; use ACI 318-19 Ch. 2 definition of f'c and 26.12 strength testing to confirm that ACI 318 strength acceptance is based on the specified compressive strength at 28 days unless another test age is designated, so the default verification age is 28 days.
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