Three consecutive standard-cured acceptance-age strength-test results for a 4,000 psi mix are 4,100, 3,980, and 3,920 psi. Under the ACI 318-19 average-and-low-test criteria, what is the result for this set?
Correct Answer
C) Pass; the average is 4,000 psi and no test is below 3,500
The three-test average is (4,100 + 3,980 + 3,920)/3 = 4,000 psi. The lowest test, 3,920 psi, exceeds 4,000 − 500 = 3,500 psi. This set satisfies the two checks. These are strength-test results, each based on the required cylinder group, not individual cylinders. Other test sets and project requirements still need evaluation. Source: https://www.concrete.org/frequentlyaskedquestions.aspx?faqid=13
Why This Is the Correct Answer
The three-test average is (4,100 + 3,980 + 3,920)/3 = 4,000 psi. The lowest test, 3,920 psi, exceeds 4,000 − 500 = 3,500 psi. This set satisfies the two checks. These are strength-test results, each based on the required cylinder group, not individual cylinders. Other test sets and project requirements still need evaluation. Source: https://www.concrete.org/frequentlyaskedquestions.aspx?faqid=13
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