Testing of Cement Questions and Answers

Answer: A

Correct answer: the expansion disrupts concrete that has already hardened

Unsoundness comes from free lime or magnesia that hydrates long after setting, expanding as it does so. Because the concrete has already hardened, that expansion has nowhere to go and cracks and disrupts the member from within - with no remedy but removal. It is the reason soundness is tested before the cement is used and never inferred afterwards.

Answer: B

Both are true and the reason gives the necessity: nobody can wait years to release a consignment, so boiling or autoclaving compresses the timescale into hours at the cost of some realism. The correlation with field behaviour is accepted rather than exact.

Answer: C

The first two are correct. The third ignores the physical requirements, and a cement may satisfy every chemical limit while failing on setting time, soundness or strength. Compliance requires every clause to be satisfied together.

Answer: D

Indian grades, European classes and American types each use their own definitions and test methods. Comparing them requires care, since a nominally similar figure may have been obtained differently. Direct substitution between systems is rarely safe without checking.

Answer: A

Correct answer: a trial mix using the intended materials and proportions

A mortar cube result characterises the cement under standard conditions with standard sand; it does not predict what the same cement will do with a particular aggregate, water-cement ratio, admixture and placing method. Only a trial mix with the intended materials answers that, and it is why trial mixes are required for structural concrete however well the cement has been certified.

Answer: B

Cement testing classifies the binder under standard conditions, while concrete testing measures what a particular mix achieves. Both are necessary and neither substitutes for the other. One classifies the material and the other qualifies the mix.