Spot the odd statement
Correct Answer: D. single-size aggregate
📚 Detailed Explanation: Shape Classification vs. Grading Classification
Aggregates can be classified in multiple ways: by shape (how particles look geometrically) and by grading (the distribution of particle sizes). These are two completely separate classification systems. Mixing them up is a common exam trap.
Why D (single-size aggregate) is the odd one: Options A, B, and C — rounded, irregular/partly rounded, and angular/flaky — all describe the shape of individual aggregate particles. These are shape-based classifications from IS 2386 (Part I). “Single-size aggregate,” however, describes the grading (size distribution) — it means the aggregate has been screened so nearly all particles fall within a narrow size range. This is a grading term, not a shape term, making it the odd one out.
Shape vs. Grading Classification
| Classification Basis | Types |
|---|---|
| Shape (IS 2386 Part I) | Rounded, Irregular, Angular, Flaky, Elongated |
| Grading / Size distribution | Well-graded, Gap-graded, Single-size (uniform), All-in aggregate |
Key Concepts for Students
- Shape affects bond strength with cement, workability, and aggregate packing.
- Grading affects void content, cement paste requirement, and concrete density.
- Single-size (uniform) aggregate has high void content; it is used in no-fines concrete and drainage layers, not in structural concrete.