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Q: To check the quality control of a concrete mix design, the total number of test samples required to constitute an acceptable record for the calculation of standard deviation shall be :
  • A. not less than 30
  • B. not greater than 30
  • C. less than 25
  • D. greater than 25
Correct Answer: Option A - As per IS : 456 : 2000 clause (9.2.4.1) • The total number of test strength of samples required to constitute an acceptable record for calculation of standard deviation shall be not less than 30. • Attempts should be made to obtained the 30 samples, as early as possible, when a mix is used for the first time.
A. As per IS : 456 : 2000 clause (9.2.4.1) • The total number of test strength of samples required to constitute an acceptable record for calculation of standard deviation shall be not less than 30. • Attempts should be made to obtained the 30 samples, as early as possible, when a mix is used for the first time.

Explanations:

As per IS : 456 : 2000 clause (9.2.4.1) • The total number of test strength of samples required to constitute an acceptable record for calculation of standard deviation shall be not less than 30. • Attempts should be made to obtained the 30 samples, as early as possible, when a mix is used for the first time.