Difficulty: Easy
Correct Answer: With passage of time, the strength of cement increases
Explanation:
Introduction / Context:
Bagged cement deteriorates during storage because of slow moisture ingress and carbonation. This ageing reduces its potential strength compared to fresh cement. Understanding which statements reflect this reality is crucial for quality control and inventory management.
Given Data / Assumptions:
Concept / Approach:
As cement ages, early hydration and carbonation of the powder reduce reactivity. Therefore, the potential strength achievable at a given water content and curing regime decreases. Typical guidance notes strength losses of tens of percent over months; after two years, the loss can approach about half for poorly stored material. Concrete made from aged cement still hydrates and gains strength with curing time, but it starts from a lower reactive baseline and rarely reaches the levels of fresh cement concrete.
Step-by-Step Solution:
Evaluate each claim against known behaviour.(a) “Strength increases with storage time” contradicts the known deterioration → incorrect.(b) Decrease with time → correct.(c) ~50% after 24 months is consistent with many textbooks as indicative guidance.(d) Concrete still gains strength with curing time even if starting reactivity is reduced → broadly correct.
Verification / Alternative check:
Acceptance testing of stored cement often requires higher cement content or rejection to compensate for reduced activity; this confirms that storage does not enhance cement strength.
Why Other Options Are Wrong:
They align with practical experience and test data, whereas option (a) conflicts with basic chemistry of ageing cement.
Common Pitfalls:
Mixing up “strength with curing time” (which increases) and “strength potential of stored cement” (which decreases). The former is a material behaviour during hydration; the latter is loss of reactivity due to ageing.
Final Answer:
With passage of time, the strength of cement increases
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