Which of the following type of coarse aggregate is preferred in road construction, so that greatest density of road layer is achieved?
- AAny type of aggregates
- BSingle-size aggregates
- CPorous aggregates
- DAll-in aggregatesCorrect
Solution
Concept
Well-graded (all-in) aggregates give the highest density because small particles fill the voids between large ones.
Step-by-step solution
1. Density of a layer is highest when voids are fewest. 2. Single-size aggregates leave large voids between particles. 3. All-in aggregates contain all sizes, so fine particles fill the voids of coarse particles. 4. So all-in (well-graded) aggregates give the greatest density.
Explanation
All-in aggregate has coarse and fine sizes mixed in a good grading. The smaller particles fill the gaps between the bigger ones, so voids are fewer and density is higher. This gives a strong, stable road layer.
Why the other options are wrong
A: Any aggregate will not give maximum density; grading matters. B: Single-size aggregates leave many voids, so density is low. C: Porous aggregates absorb water and are weak; they do not increase density.
Shortcut
Maximum density = well-graded = all-in aggregate.
Common mistake
Thinking single-size aggregate packs better; in fact it leaves more voids.
Correct answer: D) All-in aggregates