Concrete Technology – Pick the correct statement about tests, curing, and aggregates Which one of the following statements is correct regarding concrete properties, testing, curing, and aggregate grading terminology used on site and in laboratories?
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APlain cement concrete is equally strong in compression and tension
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BThe slump test is performed to check concrete strength
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CCuring of concrete is done to achieve proper compaction of cement
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DFineness modulus is an index number expressing the relative sizes of aggregates
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EConcrete is a mixture of binder, coarse aggregate, and water (no fine aggregate)
Answer
Correct Answer: Fineness modulus is an index number expressing the relative sizes of aggregates
Explanation
Introduction / Context:Quality control in concrete involves understanding what specific tests measure, why curing is required, and how aggregate grading is summarized. Misconceptions here can lead to poor mixes, inadequate performance, and incorrect interpretation of site tests.
Given Data / Assumptions:
- Ordinary Portland cement concrete without special fibers or admixtures changing fundamentals.
- Standard slump testing procedures (workability measure).
- Aggregate grading described by sieve analysis and fineness modulus (FM).
Concept / Approach:
Concrete is strong in compression but weak in tension; reinforcement is used to resist tension. The slump test measures workability/consistency, not strength. Curing maintains adequate moisture and temperature for hydration; it is not about compacting cement. Fineness modulus is a single index derived from cumulative sieve analysis to indicate coarseness or fineness of aggregates.
Step-by-Step Solution:
Assess Option A: incorrect—tensile strength is roughly 1/10 of compressive strength.Assess Option B: incorrect—slump reflects workability, not strength.Assess Option C: incorrect—curing enables hydration and reduces shrinkage; compaction is achieved by vibration.Assess Option D: correct—FM is an index of aggregate particle size distribution.Assess Option E: incorrect—concrete includes fine aggregate (sand) as well.Verification / Alternative check:
Code-based QC procedures define slump as a workability test and curing as hydration support; textbooks define FM as the sum of cumulative percentage retained (divided by 100) on standard sieves.
Why Other Options Are Wrong:
They misstate fundamental definitions or conflate different processes (compaction vs curing, strength vs workability).
Common Pitfalls:
Using slump to infer strength; neglecting curing leading to surface dusting and low durability; ignoring the role of sand in concrete mix design.
Final Answer:
Fineness modulus is an index number expressing the relative sizes of aggregates