Correct Answer - Option 2 : Screes
Concept:
Angular aggregates:
- The angular aggregates consist of well-defined edges formed at the intersection of roughly planar surfaces and these are obtained by crushing the rocks.
- Angular aggregates result in a maximum percentage of voids (38-45%) hence gives less workability.
- They give 10-20% more compressive strength due to the development of a stronger aggregate-mortar bond. So, these are useful in high strength concrete manufacturing.
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Example: Crushed rocks of all types; talus, screes, etc.
Flaky aggregates:
When the aggregate thickness is small when compared with the width and length of that aggregate it is said to be flaky aggregate. Or in the other, when the least dimension of aggregate is less than 3/5 of its mean dimension then it is said to be flaky aggregate.
Example: Laminated Rocks, both naturally occurring as well as crushed
Elongated aggregates:
When the length of aggregate is larger than the other two dimensions then it is called elongated aggregate or the length of aggregate is greater than 9/5 of its mean dimension.
Rounded aggregates:
Natural aggregates smoothed by weathering, erosion, and attrition. Rocks, stone, sand, and gravel found in riverbeds are your most common rounded aggregates. Rounded aggregates are the main factor behind workability. These have the minimum percentage of voids ranging from 32 to 33%. It gives the minimum ratio of surface area to given volume and hence requires minimum water for lubrication.
Example: Rocks, stone, sand and gravels.
