Concrete testing — the slump test of fresh concrete is primarily used to assess which property? Pick the most appropriate parameter.
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AStrength
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BDurability
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CWorkability
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DWater content
Answer
Correct Answer: Workability
Explanation
Introduction / Context:Before placement, concrete must be workable enough to be transported, placed, compacted, and finished without segregation or excessive bleeding. The slump test is a quick field indicator of consistency/workability and is widely used for quality control on site. This question ensures you identify the property directly evaluated by the slump test.
Given Data / Assumptions:
- Standard Abrams cone, standard rodding and lift procedure.
- Measurement is vertical subsidence (slump) in millimetres.
- Mixtures may vary in water, admixtures, and aggregate grading.
Concept / Approach:Slump is an empirical measure of the ease of flow/consistency of fresh concrete. While water content influences slump, the test does not directly measure strength, durability, or precise water content. It provides a comparative index of workability for mixes of similar composition.
Step-by-Step Solution:
1) Fill and rod the cone in layers; lift the cone vertically.2) Measure the drop of the concrete top relative to the cone height (slump in mm).3) Interpret values: higher slump generally indicates higher workability (within limits).4) Use alongside specifications to accept or adjust the mix on site.Verification / Alternative check:Standards (e.g., IS/ASTM) define slump classes for different placement methods, confirming its role as a workability indicator.
Why Other Options Are Wrong:
- Strength: Determined on hardened specimens (compression tests).
- Durability: Multi-factor property inferred from permeability, cover, mix design—not measured by slump.
- Water content: Influences slump but is not measured directly.
Common Pitfalls:Using slump to compare dissimilar mixes; ignoring temperature and admixture effects on workability.
Final Answer:Workability