Pick up the correct statement from the following
Correct Answer: D. All option are correct
📚 Detailed Explanation: Angularity, Shape Superiority and Surface Texture
This question tests knowledge of three distinct aggregate properties that are all described correctly in the given statements. Understanding each individually makes it clear that all three statements are accurate.
Why D (All option are correct) is correct: Statement A — The angularity number is defined as the percentage of voids in excess of 33% (the reference void content for rounded aggregate). It quantifies how far the aggregate deviates from the ideal rounded shape. Statement B — Angular aggregates provide better mechanical interlock and surface bond with cement paste, making them superior to rounded aggregates for structural concrete strength. Statement C — Surface texture is indeed governed by the parent rock's hardness, grain size, pore structure and mineral fabric; these are inherent geological properties.
Summary of the Three Properties
| Property | Definition / Key Point |
|---|---|
| Angularity Number | % voids above 33% reference; higher = more angular |
| Angular vs Rounded | Angular = better bond; rounded = lower voids but weaker bond |
| Surface Texture | Determined by parent rock mineralogy and geological history |
Key Concepts for Students
- Angularity number of 0 = perfectly rounded aggregate; typical crushed stone has angularity numbers of 7–11.
- IS 2386 (Part I) covers the angularity number test using a specific cylinder and filling procedure.
- Surface texture ranging from smooth to rough affects the workability — rougher aggregates need more water for the same slump.